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Take a Brake!

A Step By Step Guide to Replacing Pads, Disks & Overhauling Callipers

Introduction

Well, when Jacqui had her MOT, I got an 'Advisory' on the state of the brake disks, that were noted as being a bit rusty, and told I'd b best to get them changed before the next test. Eight months on, and a trip to Wales, doing more miles in one go than I usually do in a couple of months, the familiar grating noise of metal on metal was heard!

Strange, echoes of Bert here, and I am getting some curious Land-Rover Deja Vu! Coming back from Weston with the Caravan on Jacqui, we ran out of steam, just like we had in Wheezil, coming back from Wales we develop a rear hub fault, just like we did in Bert! Better make sure I don't go to any scout Gang Show's in Staffordshire, 'cos it was coming back from one of them, Bert's engine boiled over leading to the infamous V8 tear-down!

Any way, to the point, brakes, and over-hauling them. MOST of the time, you can just get away with changing the pads, and in my case, I could probably have done so too, except for that advisory, cautioning the amount of rust in the venting. So a pad and disk change then?

Well, no, because sure as eggs is eggs, come to put the new pads in, and you are pretty likely to find a sticking calliper piston. In my case, I'm pretty sure of it, I think that one of them was sticking before the pads went, possibly leading to a bit of dragging, and premature wear, but even if that's not the case, as the pads wear, the pistons poke further and further out of the calliper, accumulating more and more crud, and when you come to push them back in to fit new, thicker pads, they don't want to play ball.

Give them a bit of persuasion, and they may go back in, but that's often a recipe for the corroded piston to cut up the tired old seal, which isn't good. An 'Overhaul' kit for a Range Rover or Land-Rover calliper is less than a fiver, so it seems a prudent investment. With it, you can remove the calliper, take the pistons all the way out, clean them thoroughly, inspect them, and if necessary replace them, again they aren't THAT expensive, less than a fiver each, but either way, renew the seals, and put them back together, fairly certain that they will work well and reliably for a fair old while.

Worth noting, that the Land-Rover spares emporiums list rear calliper on a Rangie for around 50 each, fronts for around 90. Five quid for an overhaul kit, and five for each piston you need to replace, and a DIY overhaul, changing ALL the serviceable parts will cost you about 15 for a rear calliper, and 25 for a front. THAT is a BIG saving, for a little time and effort!

So, three jobs;

But, to take the disk off you need to dismantle the hub; and when it's all back together again, we need to bleed the system through, so w may also need to have a look at:-

First of all - Jack the Wheel

First of all, loosen the wheel nuts, jack the axle, and remove the road wheel.

Note here that the wheel nuts and the drive flange are all nicely covered in coppa-grease. Whoever worked on this before, must have been a kind mechanic. Oh yes, he was. That's right, it was me!

Seriously, I say this a lot but removing the wheels on a spare Sunday afternoon, before you give it its monthly wash, and coppa-greasing the nuts and flange, and then putting it back together with the wheel nuts tightened by hand with the standard wheel brace is well worth the effort.

It means that when you come to do a job like this, you don't have to waste half your time, and skin your knuckles before you even get into the job proper, and should you end up stranded with a flat down some lonely lane in the middle of no-where, you'll know that you can fix a flat with the minimum of hassle.

You REALLY don't want to find out that the nuts have been done up to 160ft-lb and you cant undo them with the wheel brace, or that they have corroded solid, or that the wheel has corroded onto the drive flange, on a cold wet hard shoulder in the dark of a winter rush hour.

Any way, the wheel is off. In this case nice and easily. So get it on an axle stand, and chock the front wheels before you do anything else, and the whole lot falls on you.

Part 1 - Brake Pads - Removal & Refitting

Part 1; Step 1 - Remove the brake pad retaining pins

 

Stick your head under the wheel arch and have a look at the top of the calliper, and you'll probably see something like this. It may benefit from a quick dust off with a wire brush to remove loose crud and rust, to let you get at the bits and pieces more easily, but what you are interested in first, are the two pad retention split pins, indicated with the yellow arrows in the first pic.

They should be bent over to hold them in place at the back. standards and practices vary; some people bend just one side, others both, and sometimes into curious shapes. If possible, straighten them out at the back, so that you can pull them back through, as shown in the middle pic. You may have to twist the heads to get at the the 'tang'.

If they are particularly stubborn, just cut them through the middle, over the brake disk, in the middle of the calliper, and pull the ends out from either side.

Part 1; Step 2 - Remove Anti-Rattle Clips, and Pads

The anti-rattle clips are the thin metal plates that sit over the pads, under the pins, and they will probably 'ping' out of the way when you draw the pad retaining pins, but if not, lift them out of the way, and keep them safe.

If you try and tug the pads out, though, they will probably be a bit tight, held in place by the piston. If the piston is reasonably 'free' you should b able to loosen them off by waggling them, or giving them a couple of light taps with the end of your hammer handle.

If they are a bit more stubborn, and / or the piston is seized, (as in my case), I introduce, 'General Purpose, Specialized Tool 24'... a small G-Clamp! Useful little gizmo's and this one will be getting a lot of use in this article. You can usually get them from a hardware store or off a market stall, for a couple of quid, or 5 a pair, which is well worth the investment. Alternatively, most motor-factors sell 'piston retractors' that work pretty much the same way, but have more conveniently shaped clamps to get into the calliper.

Using the bracket end on the calliper, and the screw end on an exposed bit of pad, you can use the clamp to wind the piston a bit back into the calliper, and make some clearance to get the pad out, as shown in the second pic.

IF you are not going any further, and are simply replacing the pads, you may want to wind both pistons as far back into the calliper as you can, so that you have room to get the new pads in. If you are carrying on, and doing a calliper overhaul, then it can be helpful to leave the pistons poking out a bit.

BUT, in either instance, follow next step, and decide what you want to do, first.

Part 1; Step 3 - Inspection of Pads, Pistons & Disk

Pads

The first pic, shows three brake pads, the lower two the ones I removed from my calliper, the upper one 'A' a brand new pad. 'B', is 'Bad', it is thin, and shows signs of uneven wear, but is probably still serviceable. 'C' though, is 'Chronic'! There is absolutely NO pad material left on the backing plate, and THAT pad has been rubbing metal on metal on the disk!

IF you have pads, as I did, where one is obviously a lot more worn then the other, it's a good indication of a sticking calliper piston.

If you have a pad, as 'C' that has worn right through the pad material, then look VERY Closely at your disks, because rubbing metal on metal, it could have damaged or scored it, and it's likely it may need replacement.

Pistons

The next picture shows the calliper, actually removed from the axle. I took it off because I knew it was going to come in for attention, but also, it was easier to photograph the detail. But you should be able to see all of the pertinent bits with the calliper still attached.

See the piston protruding from the calliper; it's not very nice, its got a layer of at least surface rust and crud on it, and probably some flaking of the chrome, if not pitting.

THIS is why I suggest you DON'T wind the piston all the way back into the calliper when you take the old pads out. If you do, then you will force all that muck and corrosion past the piston seals, with two possible results.

Pay heed, most 'serious' braking faults, occur shortly after a pad replacement, and these are the primary causes!

Something else to note, rear brakes tend not to wear out as fast as fronts. Most cars are 'nose heavy', but even those that aren't, under braking you get a 'weight shift' to the front of the car, so more weight on the front wheels, hence more traction, hence greater braking effect. This is why most cars have disks on the front and drums on the back, or bigger disks and or more powerful callipers at the front to at the back, as well as 'duel circuit' brakes and compensating valves to 'balance' the braking effect at either end.

Anyway, point is, that with most braking effort coming from the front, the front pads tend to wear out faster than the backs, and so get changed more frequently, especially if the car is not often heavily loaded with luggage or passengers over the back axle. This means that rear brakes are often neglected, and have far more time between services, for the pistons to corrode up as mine have.

The other fault you should be looking for, this calliper has also suffered, and that is deterioration of the seals. If you look closely, you can actually see, around the base of the piston, shreds of rubber ripped away from the wiper seal. This does not bode well, and really demands that the calliper be properly overhauled with new seals.

Often, failure is not as obvious, so look closely, both for signs of deterioration on the seal, but also the tell-tale of any brake fluid weepage. In this case, there was no dampness, either on the piston or around the calliper, which suggests that while the outer 'wiper' seal has 'gone', the inner fluid seal, is probably 'OK', but with that piston, and the wiper seal demanding over-haul, it's going to get changed any way.

Disks

Disks can be tricky to assess visually, and even more tricky to measure empirically! In my case, I had that 'Advisory' on them, so they were going to get swapped out, But.... The book tells you that there is a minimum disk thickness. Look at the edge of the disk, though, and it will probably look pretty good.

But, one of the reasons you had to wind the calliper pistons back in to get the pads out, was that the pads don't bear right on the edge of the disk, and they will tend to wear a 'groove' in it where they do rub, leaving a 'lip' on the edge, and you have to pull the pads past this to be able to lift them out.

Pic shows the 'rubbed area' with arrow 'A'; and the lip with arrow 'B'. Also shown is scoring, the rough ridges and grooves denoted by arrow 'C'

The Haynes goes into some length about how to measure a disc up with a Dial Test Indicator, to check the thickness and the 'run-out'... If you have a DTI and the knowledge to use it, feel free, other wise such procedures are, for the amateur best farmed out to a professional machine shop, who would expect the disc removed from the car... and would probably charge you more than most factors would for a new disk... so if in doubt, you might as well just replace it. Rear discs for the Range were actually cheaper then the pads, so not an inordinate expense, just a bit of a pain to fit.

You can measure the disc thickness with a vernier gauge, and digital 'calipers' are now often less than a tenner, and handy to have in the tool box, however to be able to measure the rubbed area you will have to get past the step on the edge of the disk.

I put two 1/4" drive sockets between the jaws, then 'zero' the caliper, open them out, put the sockets on either side of the disk, on the rubbed area, then close the callipers round all three. Having zero'd the caliper on the height of the two sockets, reading should be the thickness of the rubbed area of the disk.

Alternatively, you can use a 'short steelie', or small steel ruler. Does need to be an engineers rule though, with the scale starting right from the edge. As a rough reckoned, this is probably good enough.

Measure the thickness of the disc at the edge, mine was 15mm give or take 1/2 a mm or so. Then put the steelie end on against the rubbed area and the wear ridge. and measure how high it is. In my case it was about a mm and a half, give or take a bit.

Marking on the edge of the disc says min thickness 11.7mm, or about one and a half mm wear on either side, so if its much over a mm on the side you can get at, it's pretty much a judgement call, anything less and you should be pretty much OK, PRESUMING of course that the wear's pretty even on both sides.

If in doubt, swap it out!

Scoring, though is another question, and that is very much subjective. A disc will actually work a bit better when a bit 'roughed up', it gives the pads something to bite into, but ridges and grooves can make measuring the thickness a bit more awkward, your measurements will be from the top of the ridges; so make the reading a bit 'low'.

This disc wasn't that great, one of the brake backing plates had actually been rubbing against it due to a sticking calliper piston, but that was on the other side. Front side, seen in the picture was marginal. Ridges weren't too wide or too deep, and fairly even across the rubbed area. If the ridges are more pronounced, or there are some that are visibly deep, then its prudent to not use the disc. Again.

If in doubt, swap it out!

If you are happy that these operations aren't needed, or have already done them, then continue, with straight pad replacement, as final steps, putting it all back together again.

Part 1; Step 4 - Replace Pads

Pictured during the calliper overhaul, with the calliper off the car and on the bench for ease of photography, I fitted the pads up before putting the calliper back on the car. If you are undertaking a calliper overhaul, you may want to do likewise, but it's probably easier to fit the pads after the calliper is replaced.

The picture, though, makes it nice and easy to see where the pads live, without a disc in the way, though you should be able to see it all with the calliper and disc 'in situ'.

The first step, if you haven't already done so, is to completely retract the pistons into the calliper. They may 'push' in by hand, or you may use a specialised calliper piston retractor tool, or my 'General Purpose, Specialized Tool 24', as shown earlier, or as again shown in Part 2; Step 9 - Fitting the Pistons, bearing directly on the piston, rather than 'skew' on the top of the old pad. The pistons need to be fully retracted, so that there's enough clearance to get the thick new pads in either side of the disc.

However, the calliper will probably be full of corrosion, crud and old brake pad dust, and before you try and fit the new pads, it's worth giving it a good going over with a wire brush and scraper Again, indication of where to pay particular attention is given in Part 2 - Brake Calliper - Removal & Overhaul, but the main area of attention is the pad guides, which are in the corners of the calliper casting, that the two red arrows facing forward in the pic are indicating.

A lot of crud tends to accumulate here, and will have built up behind the old pads as they wore and were pushed closer to the disc by the piston. With the piston pushed all the way in to fit new pads, it's likely that the new pads will be a tight fit or not seat nicely with that crud in the way. Easiest way to remove it is a good scrape with an old blunted screwdriver or chisel. There are proprietary 'brake calliper' cleaning solvents on the market, but to b honest, I've never found one that shifts the accumulated muck as quickly or effectively as a good old fashioned scrape!

Don't be too eager to wallop the new pads in and get on, give this preparation plenty of attention, because it is well worth it, the pads go in an awful lot more easily, and the brakes tend not to develop squeaks or start dragging so readily.

So, thoroughly cleaned up in the guides, they should be treated to a smear of coppa-slip. Coppa grease was developed especially for this job, and though it has a multitude of other uses, THIS is what it is really for.

DO NOT use graphite grease or anything else. Coppa-grease is the ONLY lubricant designed to withstand the sort of localised temperatures you get in brakes, and not melt.

After the guides have been greased, then so can the back of the brake pad, and IF you are careful, you can wipe a smear onto thee edges that will run in the guides, just to be sure. But do be careful not to get any on the brake pad material or face. I also add a smear, as arrow to the face of the piston

All cleaned and greased up, the pads can be slid into their guides.

Part 1; Step 5 - Replace anti Rattle Clips & Pad Retention Pins

This is the nadgery bit; the anti-rattle clips tend to be a bit of a pain, and the pins can be recalcitrant.

Book tells you to fit new pins, and it is good practice, to do so. If you have had to cut the old ones out, or the old ones have been a bit mangled by enthusiastic bending to secure them, it may be essential.

Once upon a time, they used to put a set of pins in the box with the new brake pads, and occasionally new anti-rattle clips too! But these days they seem not to do so so often, which can leave you cursing trying to use the old pin, or find a Factors open at 4pm on a Sunday afternoon with a suitably long split pin in one of their oddment tubs!

Worth noting, when you order your pads, check if the box contains pins and clips, and if not see if you can order them separately, as it CAN save a lot of hassle!

Clips go on top of the pad, under the pin. Give the tangs on the clip a light smear of copper slip, and a little more liberal smear on the top where the pin goes through.

You have to make sure you get the clip in the right way round, which can take a bit of head scratching, then push the pin through the calliper, the pad and over the op of the clip, then through the hole the other side. sounds easy, SHOULD be easy, but one of those infuriating jobs where if the spring clip doesn't want to play ball, or if you have a 'kink' in the pin, you can be swearing at  the thing for ages! In which case, remember rule one, and go make a cuppa and come back to it!

Once pins are through, bend the tangs out. Tip they only need to be bent out so that they cant shake out of the hole, they don't need to be twisted into exotic shapes or bent back over the top of the calliper! That can make straightening them to get them back out next time more difficult!

Part 1; Step 6 - Final Check & Replace Road Wheel

Last job is to put the road wheel back on, and lower the car off its stands or jack. BEFORE doing so, though, have a good check round EVERYTHING you have worked on, and double check all the nuts and bolts are tightened; look at how things are seated, look at hoses and pipes and stuff and generally look for ANYTHING that looks out of place, wrong, or not quite right!

THEN go make a cuppa! Come back, mug in hand, and have ANOTHER look with fresh eyes!

Happy? Then put the wheel back on, lower the car to the ground and tighten the wheel nuts up!

After ANY work on the brakes though, do an immediate and CAUTIOUS test. Start by taking the hand brake off, and with the car in gear, or park, and the engine 'off', just pump the brakes and make sure the pedal is firm.

Next gears in 'Neutral', do a 'rock' test, which is to rock the car forewords and back with your leg out of the drivers door, and your other foot on the brake pedal..... works well enough in a Mini...... but you may need an assistant in a Landy, if you don't have a 30"+ inside leg!

Happy the brakes are functioning, progress to a 'driven test'; but again, be cautious, and as you start moving, one hand on the hand brake, just in case, try the foot brake!

Confident that they are effective, go round the block, anticipating junctions VERY carefully and give the brakes a little more effort each time. Finally, when happy they are working OK, go find a quite bit of road or industrial estate, and from 30mph in a straight line, do some braking exercises, working up from a gentle deceleration to a full emergency stop.

DON'T just try an emergency stop and if it goes ok presume all's good. A prolonged 'light' breaking can actually show up a multitude of faults, like rattles and rubbing, and 'strong' but not 'sudden' braking should show up any balance problem making the car veer, that wouldn't be so pronounced under the sudden application of an e-stop.

Also remember, that brakes take time to 'bed in', but also the warning that MOST brake faults occur after maintenance on them, particularly if you haven't done a complete overhaul, but only a pad swap.

Part 2 - Brake Calliper - Removal & Overhaul

Part 2; Step 1 - Remove Brake Pads from Caliper.

The first jobs in removing and overhauling the calliper, is to remove the brake pads from the calliper, with the calliper still attached to the axle. As shown in Part 1, following:

With that done, it's possible for the calliper to be removed. It is held on by just two bolts on the BACK of the calliper, and the brake lines. BUT before you start, for the overhaul, we will want to remove the pistons from the calliper.

Part 2; Step 2 - Protruding the Pistons

If the pistons are pushed all the way into the calliper body, it's very difficult to get them out. The further they are sticking out to begin with, the easier it is to remove them completely, first because there is more to grab hold of, and second, because there's less inside, holding it in.

The simplest way to get the pistons to protrude to the limit of their travel is, with the brake pads removed, and the calliper still plumbed into the brake line, to simply 'pump' it out with the brake pedal.

But don't rush off.

For the first problem, there are a couple of solutions. One is to remove the pads from both callipers and protrude the pistons from them before disconnecting either from the plumbing.

The next, is to completely overhaul one side at a time. Protruding the pistons on the calliper you want to work on, as you get to it, removing it, overhauling it, then replacing it, and plumbing it back in, before you look at the other calliper. (Though you may need to bleed the brakes between fitting the first calliper and tackling the second)

Lastly, I introduce improvised tool 39. Which is a 'blanking piece'.

This is a 'female' brake pipe union around a short piece of double flared brake pipe so that it will screw onto the male union that normally plumbs into the calliper. (See A Bit of Flair! for making brake pipe.)

However, having left enough pipe for the union to move up and down on, I lightly, so not to split it, hammered the pipe flat for about three inches, then filled the remaining end with solder. (Flat section is coiled up to make it a bit more compact)

Bit belt & braces, either flattening the pipe or soldering it should be enough to stop brake fluid dribbling out of the pipe, which is the main reason for making the thing, BUT, I also wanted to be sure it would hold braking pressure so that I could, IF I wanted, use it to blank the line while I pumped a piston out of another calliper.

Getting on with it then; you may find an assistant to pump the brake pedal, while you watch the calliper, useful, but with care, not essential. With the pads out, and the calliper sill around the disc, the pistons shouldn't come all the way out of the calliper, they will come up against the disc and stop with about 1/4" of piston still inside the calliper.

However, pump them against the disc, and you'll struggle to get the calliper off, as the pistons will press against the thinner, rubbed area of the disc, and wont slide past the wear ridge.

The pic shows how I used a pair of thin pieces of plate as travel stops. these mean that you can 'waggle' them out and leave a bit of clearance to get the pistons past the wear ridge on the disc as you take the calliper off.

Another improvised tool, these are actually bits of an old bracket, but an old baked bean can hammered flat would do just as well!

With the travel stops removed, you should be ready to move on, BUT, if one or other piston is sticking (this is where watching the pistons come out as your assistant pumps can be helpful, watch for one piston coming out before the other starts moving) you may want to 'pump' the pistons out of the calliper BEFORE you uncouple the brake line.

If the pistons look or seem sticky, you may want to leave the calliper plumbed in until it's removed from the axle; so skip ahead to Step 5A - Alternative 'Popping' the Pistons, and remove the calliper, but DON'T lift it all the way off the axle, just off the disc, and with it still connected to the brake line, pump the pistons all the way out of the calliper, before undoing the brake line. But see relevant step, its fiddly, and it's messy!

Part 2; Step 3 - Uncoupling the brake lines

(IF you are NOT removing the calliper for overhaul, merely to allow replacement of the disk, then you may not need to disconnect the brake lines. Not undoing the brake lines, can then save having to bleed the brake system through. See Part 3; ALTERNATIVE Step 2 - Removing Calliper, without disconnecting Brake Lines)

The first picture shows me unfastening the union to the calliper on a rear brake, attached with a single 'hard-hose'. The second picture shows some of the plumbing on Jacqui's front callipers. Because she is a later EFi model, she had duel circuit, four piston front callipers. Older models, I seem to recall had single circuit, four pot callipers, (I think Bert had them), while very early examples I THINK had twin piston callipers, like the back. Point is, plumbing arrangements vary.

Important thing is, that there are 'hard-hoses' and there are 'flex-pipes', and you may have one or the other, or both to undo. On Jaqui's fronts, there's both.

For hard hoses, care is needed, because the pipe often corrodes into the union. When you come to unfasten them, the pipe will twist with the union and shear through, which is not too helpful.

To try and avoid that, loosen off, or remove the plumbing from the calliper BEFORE loosening or removing the calliper from the axle. This means that you have something solid to twist against. Then, whilst you are turning the union, hold the pipe steady with your other hand. If it's a bit stiff, it's often useful to 'waggle' the union, 1/4 turn or so back and forth to break the grip between the union and the pipe, before trying to unwind it all the way from the calliper.

If the hard hose starts to twist, then just cut the pipe through, before removing the union. The pipe will need replacing, but see A Bit of Flair! for how to make up your own replacement.

On Flex-Pipes, you have a little more 'give', but the hose screws in to the calliper housing at one end, and twisting the hex-head to unscrew it will twist and strain the pipe. If it 'kinks' you can internally collapse the pipe, so you need to undo the other end, usually connected to a hard hose, via a bracket, before winding it out of the calliper.

In Jaqui's case, there are two brackets, one on the swivel, and one on the inner wing, and the flex-hose connects to hard-pipe at either end, so it's easier to undo the hard-pipe on the calliper, as for a rear calliper, to remove it, but the swivel end bracket needs detaching before the calliper can be removed.

With the brake lines disconnected, it's helpful to put the loose end into a plastic bag, taped around the loose end, to catch any fluid that dribbles out, to save mess, and possibly ruined paintwork, as brake fluid is corrosive.

Alternatively, I return to improvised tool 39..... stops dripping, so no wasted fluid, less bleeding to do, and no corrosive mess!

See A Bit of Flair! for making brake pipe. You can make up a blanking piece with any union on the end to suit. The pipe's a few pence, the union a few more, so they cost less than 50p and a little time. And I reckon that they are REALLY useful!

Books tell you that you can use 'brake hose clamps' on flex lines, but personally I don't like them, and find their usefulness limited. On a front brake, the flex hoses are usually fairly close to the calliper, so the clamp will 'choke' the hose near the end, and close to where you are working. On the rear, though, particularly on a live axle car, like a Land-Rover, the flex hose is in the middle of the axle, so not so close to where you have disconnected, leaving a lot of fluid downstream of the clamp to leak out, as well as being more awkward to get to.

However, MAIN reason I don't like pipe clamps is that I am VERY nervous about collapsing the brake line! On standard rubber hoses, they may work OK, and the rubber may 'revert' to its original shape OK, BUT, if the hose is a bit old, it is likely to have gone hard, and you CAN cause the pipe to crack internally, which can lead to it 'ballooning' internally. Possibly not a high likelihood, but I don't like to risk it.... I've rarely had the luxury of nice new hoses on my cars!

Other thing is that you cant use them on braided hoses, or reinforced 'nylon' hoses. Reinforced nylon hoses, often look like standard rubber, but they have a nylon tube running inside them. Stiffer than rubber, they offer better braking feel, but are still 'flexible', but squash one and the nylon WILL crack, as they don't have the elasticity of rubber. Braided hoses, usually have a nylon inner tube, so would have the same problem, BUT there's a stainless steel armour 'braid' around the outside.... crush that and the steel WONT spring back..... though you'd be lucky to squash it with a hose clamp!

Hence I find blanking pieces far more reliable and convenient, and made from off-cuts of pipe, or failed flares, the few pence they cost a LOT cheaper than a clamp!

Part 2; Step 4 - Un-bolting the Calliper

With the brake lines disconnected, the calliper can be unbolted from the axle. NOTE: Calliper bolts are BEHIND the hub

I say this because there are some bolt heads on the front of the calliper, but if you undo these you could be in real trouble - they hold the two halves of the calliper together, and they are NOT supposed to be 'user serviceable'. That is to say, that there are seals between the two halves that aren't usually available to the public, and if you cant get them, then undoing the wrong bolts COULD prove expensive, as the only way to fix it will be to buy a new calliper!  (See footnote 'Splitting Callipers')

So, take a look, bolts to be undone are the ones highlighted in the yellow circles in the picture on the left, that have sockets on them, so you can see where they are more clearly under all of the dirt! Picture on the right, shows the front of the calliper, with the two bolts you shouldn't touch, highlighted in yellow circles, with red crosses through them!

With the bolts un-done, the calliper can be lifted away from the disk and axle, for overhaul operations, 'on the bench'. So I don't loose them, I screw the calliper bolts back into their holes on the axle.

Part 2; Step 5 - Pulling the Pistons

Before you start, the calliper is probably covered with a lot of flaky old rust and or brake dust and road crud. So before exposing the innards, its a good idea to get as much of that off as you can to begin with, with a thorough wire brushing and a bit of scraping with a blunted screwdriver or chisel. Pay particular attention to the brake pad 'guides' inside the gap in the calliper, in the corners.

In this case both pistons were pitted & corroded beyond redemption. If they are only lightly corroded and have only 'spots' of dimpling on them, then they can usually be salvaged by lightly cleaning them up with diesel wetted fine grade wet & dry sand paper.

From the pic on the left, if the pistons aren't too bad, they SHOULD waggle free by hand, with a little twisting and tugging. More stubborn slugs might need a bit more persuasion, as the pic on the right which I am twisting and tugging with a pair of pip grips! THIS is certain to dent and score the finely ground surface of the piston, and if you have to resort to this kind of treatment, then it is probably best to scrap the piston and replace it. Amount of corrosion on this one, though mad that an inevitability any way!

As the piston comes out, it will release all the brake fluid that's in the cylinder through, so do do it somewhere that wont matter, like in an old washing up bowl, and have a rag or something underneath to mop it up.

Part 2; Step 5A - Alternative 'Popping' the Pistons

If the pistons are VERY stuck, or you don't have enough protrusion to get a good enough grip, then you may need to use the hydraulic pressure from the brake line to push them a bit further, or even ALL the way out.

NOW, idea is to plumb the calliper back onto the brake system, and pump the brake pedal, until the piston comes free.

Murphy's Law, will mean that you'll discover this necessity ONLY after you have prised one piston out, which means that you cant put the calliper back on the line to pump out the other! Trick here is to put that piston BACK! and hold it in with specialised tool 24 (G-Clamp!) while you do the other.

OK, warnings about re-using old seals and such, but you are ONLY putting it back JUST to get the other out, so don't worry too much, it doesn't matter if it leaks a bit, you are going to release a whole LOAD of fluid in a minute ANY WAY! One tip, if you have already flooded your work area with fluid taking that piston out, fill the calliper cylinder with fluid before refitting the piston!

Right, this will probably be a two man job; one to pump the brake pedal, and the other to hold and fiddle with the calliper.

First of all, you will ONLY be able to 'pop' one piston, as mentioned, so with the calliper on the brake line, hold it around the disc, and using some plate pump the pistons out as far as they will go, as step 2 - protruding the pistons.

Now, lift the calliper away from the disc, just far enough to get clearance in the gap, but NOT so far as to stress the brake pipe. Again, some creativity with home-made pipe can give you a bit more 'play', and using a couple of lengths of old flex hose and some made up unions can mean you can actually put the thing on the floor while you work and not worry too much about the brake pipe on the car, though you may have to bleed the extension pipe through before you can get it to take pressure.

Next, 'set' the least sticky piston with the G-Clamp to stop it coming all the way out before the other, does, THEN put the calliper in a polythene carrier bag, ready to catch ll the 'bits' and the fluid that will go every where as the piston 'pops'.

Once set up, pump the brake pedal, and the hydraulic pressure SHOULD pop the sticky piston right out of the calliper. It will be followed by a flood of brake fluid, and possibly the wiper seal, hence the carrier bag. But it will be 'out', so now you can unfasten the G-Clamp, on the other piston, and pull that one out by hand, and uncouple the brake pipe, and go work on it on the bench.

Part 2; Step 6 - Removing the Seals

There are two seals in each calliper cylinder. The outer on is retained under a bezel in a rebate around the top of the cylinder, the inner in a groove in the cylinder wall. Both will 'pry' out with a blunted screwdriver, as shown.

 

The outer seal, usually pops out fairly easily, but the inner one can be a bit more awkward, and may need 'stabbing' with something a little sharper to get a start, but once lifted from the groove, it will usually pull out readily enough.

Be CAREFUL! The calliper relies on a close tolerenced 'fit' between the piston and the cylinder, and you don't want to be gouging any auxiliary grooves in it!

Take not; the seals you remove may look in pretty good shape, but NEVER be tempted to re-use them. Brake fluid contains special solvents known as 'seal swellers' that actually soak into the neoprene rubber of the seals in the system, making them 'swell' and provide a greater sealing pressure.

As soon as you take a piston out of a calliper or master cylinder, you relieve that pressure, and the seal will NOT swell any more, so will lack sealing ability.

Remember the 'caution' in step 4 about not undoing the bolts that hold the two halves of the calliper together; there's a rubber seal between the two halves, where the brake fluid is 'ported' between the cylinders on either side; it's not in the spares catalogue, and if you split the calliper you wont b able to replace that seal (at least not with an 'assured' like for like replacement), and re-using the 'old' seal will almost certainly result in the seal not sealing. (See footnote 'Splitting Callipers')

Part 2; Step 7 - Cleaning up the Calliper

I struggled to get decent pictures of the 'innards' of the calliper. All awkward angles, and if I could actually 'see' something with the camera, then trying to light it properly without getting white-out or heavy shadow proved a nightmare! These were the best I could do, I'm afraid!

First pic then, I am using my blunted screwdriver to scrape clear the outer seal rebate. Care is needed, the 'flat' is something you don't want to score, but the seal is held against that flat by a steel ring sitting against the edge of the rebate and in the corner, and the old one will tend to leave a lot of crud and corrosion behind it.

When it comes to fitting the new outer seal, that retaining ring can be a right royal nightmare, but it helps if you have got that rebate as crud clear as you can to begin with.

Second pic shows me using that blunted screwdriver again to pay a bit more attention to the pad guides, as mentioned earlier. That's the point where most old brake dust, road crud and corrosion tends to build up and where thee pads often 'stick' and chatter or squeek.

Having paid attention to those two areas, it's worth looking inside the cylinder. As some of the shots show, you can get a build up of 'fur' for want of a better description, and where the old inner seal was pulled out, there will usually be a gummy residue.

It's NOT recommended to use anything either solvent based or abrasive to clan this lot out; you do NOT want to leave any chemical in there that might contaminate the brake fluid, nor anything abrasive that can score wear or worry the close tolerances or seals.

I use an old nylon toothbrush and a little old brake fluid to 'scrub' out the cylinder and seal groove, then wipe with a lint free cloth. If you are patient, it's usually enough.

IF the calliper gets wet, make sure that it is THOROUGHLY dried out; leave it in th hot sun for a few hours, or on a radiator or something of that ilk. Don't rely on just wiping it dry.

BLEED NIPPLES

Often forgotten, but after cleaning the calliper up, undo the bled nipple! If it shears, you will need to hoik it out with an EZ out! And it is FAR better to find out that the nipple is seized when you can mess about with it on the bench, or even take it to a pro-machine shop to get removed, than it is to completely overhaul the calliper, and only discover its a 'bit stubborn' when you have put it all back together and on the car and are trying to bleed the system through. Here speaks the voice of experience!

If it's 'free' though, all well and good, and it can be nipped up finger tight and not worried about until everything  is sorted, though for a few pence, you may want to renew the nipple any way.

Part 2; Step 8 - Removing the Seals

I struggled with thee pictures here too, and didn't manage to get anything half reasonable for fitting the inner seal, which is the one to do first, really. It's not too tricky though, and its just a case of flexing it a little and squeezing it into the groove, though a little care is needed not to twist it, so fiddle it in, and check its seated square, and then fiddle it a bit more to make sure its seated comfortably all the way around.

Also, be sure that you use the correct seal. In the kit are two different kinds of seal. The inner seal is a plain square section, with flat sides. The outer seal, is thinner, and has a 'double-lip'. The inside face that wipes on the side of the piston has a concave 'V' shape form, so that there's a lip, top and bottom.

 

And it's that outer seal, that is a bit of a bludger to fit. Actually, the SEAL isn't the problem, its that little metal ring that holds it in that's the tricky thing!

First pic; the ring seems to big for the hole. Middle pic; a little bit of 'persuasion' results in 'whoops!'. Last pic, they DO go in, ultimately, if you don't loose your patience and sling the whole calliper through a window first!

OK, so a few how NOT to do it. First of all, look at that last pic. If you look carefully, again, apologies for the photography, but the retaining ring isn't a plain 90 degree 'L' shape. The outside edge is actually a little bit slanted, and the top face actually 'curves' out from the edge.This ISN'T a 'lazy' pressing off old tooling that's got past the QC, it's supposed to be like that.

The 'curve' on the top edge is intended to give a little clearance so that as the piston is pushed out when you apply the brakes, the wiper seal lip comes a little way with it before reaching the inner face of that ring. When you take your foot off the brakes, the pressure is taken off the piston; BUT, there ISN'T anything to positively 'pull' the piston back into the cylinder.

There is a bit of 'stand-off' pressure between the disc and pads, that sees them pushed a LITTLE clear of the disc, but thy would still be nearly touching, and 'something' is needed to pull the piston back JUST that fraction to get some clearance. And that 'something' is that initial bit of movement of the outer seal into the retaining ring! Because with the pressure relieved, it would rather 'drag' the piston back a bit, than slid across it.

As you let the brake pedal come back up, it wont suck much fluid out of the calliper cylinder, in fact, any 'suck' that there is is filled by the master cylinder so that the brakes 'self adjust', so that wiper seal, and the bit of 'lag' that that gap between it and the retaining ring allows, is what actually maintains the running clearance between your brake pads and the disc.

OK, so do NOT try and 'press' the retaining ring into the rebate, by pushing on that front face! push that face down onto the rubber (as many thing thy should!) and you will not have any gap for the outer seal to flex into, so it wont move forwards with the piston, and it wont be able to pull it back again after, which means that you are likely to eith brakes that 'drag' and wear out quimag0051

Right, so how DO you get it in? Carefully!

As first pic, you put the seal inside the ring and fit both together. Its faffing awkward because the thing is so thin and flimsy, but you have to push it in slightly 'cocked' then gently 'square it up, working around the rim pushing the side of the ring into the rebate with your thumb, or if you have big banana fists like me, EFFOFF carefully with the flat of a small screwdriver.

See middle pic. THAT is what happens WHEN you slip, or push too hard. Don't Panic; Don't worry; Haynes may pretend that it's a simple 'on-shot' operation, but I don't know many practiced, professional mechanics that can get these things in each and every time, first time. In fact I don't think I know ANY! (and if any-one suggested they COULD, I'd b very sceptical!)

You WILL bend, twist or other-wise 'ding' a few of these trying to work them in.

See Murphey's Law, working on the principle of the 'inverse law of sod', before I began this job, I prepared myself by buying THREE calliper overhaul kits. Each kit contains four inner seals, four outer seals and four retaining rings, which means that one kit has the same number of seals and rings as are in either ONE front calliper, or TWO rear ones.

I was only overhauling the REAR brakes so 'theoretically' I ONLY needed ONE kit to do all four cylinders! I bought TWO kits, one for each side, KNOWING that that gave me two spare retaining rings, and a couple of spare seals for each calliper, and I could afford to scrap a couple in the inevitable 'miss-haps'.

BUT, just to be on the SAFE side, and working on the 'Inverse' principle, which suggests that if I had only ONE ring per cylinder, I was Guaranteed to ding it, and if I had ONE spare, Murphy would see to it I dinged that too, just for being cocky, I bought a THIRD overhaul kit, to give me THREE times the number of rings I needed, so that I had SO many of the dang things, Murphy would 'assist' me to get them all in 'first time', so that he could laugh at me for having been so paranoid and watch me mutter about paying for so much stuff I didn't need! AND, it pretty much WORKED, and I was rather stunned, that that, on THAT calliper at last, that was the ONLY retaining ring I scrapped!

Though, as my theory on Mr Murphy goes, he did seem to look elsewhere to get his 'cut'.... and BOY did he take it! On another job, my 9" angle grinder disc shattered. It was only lightly loaded, but was running out of balance and shook itself to bits, shortly after I had run it up, ripping the guard off the grinder as it went, thank heavens THAT was there, but the guard mashing the fingers of my right hand as it went! OUCH! and STILL ouch! I'm typing this with two fingers, and keep forgetting when I go to hit the 'shift' key!)

Any way, back to the plot! These are naggery little bludgers, and there is no 'trick' to them, you just have to apply patience, perseverance, and a firm but gentle touch; but a surplus of them before you begin in anticipation of the inevitable slip, and smile when you bend one, consoling yourself that it WAS inevitable, and THAT is why you bought 'spares'.

As mentioned before, careful preparation of the rebate and making sure that it is completely clear of crud and rust before you begin will help.

Other than that, just b firm. Once you have the ring inside the rebate all the way around, don't be TOO hasty to try and push it all the way down. Press on on side, and it will just pop right the way out the other.

Apply Firm pressure with the ball of your thumb on the side opposite the one you are working on, and once you have the ring in the rebate 'flush', to drive it home, just 'LIGHTLY' use the side of that blunted screwdriver, so that you are pushing on the very edge over the top of the bit in the hole, not pushing that face into the rubber, and drag it around the rim, 'gently' squeezing the ring 'home'.

Part 2; Step 9 - Fitting the Pistons

Basically, having renewed the seals, the piston just needs to be pushed back into the cylinder, but, because the seals are 'dry', it may be a bit 'sticky'. It's also a bit awkward to get the piston in straight, it will try and twist 'cock' on you.

BE careful, because if you are pushing hard, and have only got it into the outer seal, when it twists, there's a good chance it will pop the seal, and that painstakingly fitted retaining ring out of the rebate!

First of all, give the piston a wipe over with brake fluid to help it slid in. Don't listen to any-one that suggests washing up liquid or anything! As previous comments you don't want to contaminate the brake fluid!

'wiggle' the piston past the outer, wiper seal until you feel it 'grip' on the inner seal, then GENTLY, but firmly push it as squarely as you can. Slow gentle pressure, and it WILL go in.

Once you have worked it in about half way BY HAND and it is square in both seals, you can use 'General Purpose, Specialized Tool 24', to carefully pull it 'home'.

Repeat the operation on both sides, or on all four pistons, if you are doing a front, and THAT is about it, calliper is overhauled, and SHOULD be good, all you need to do, is put it back on.

Part 2; Step 10 - Re-Fitting the Calliper to Axle

Pretty much the reverse of removal, as they say. IF you are replacing the brake disc, though, then you will need to complete that task from Part 3; Step 3 - Removing the Hub, to Part 3; Step 6 - Replacing the Hub., which will actually redirect you to, Hubs Inspection, Maintenance & Overhaul, for the actual hub removal and replacement. So as far as this bit's concerned, I'll presume that the disc is on the hub, and the hub securely on the axle.

As shown, the calliper needs to be slid onto the brake disc, and the mounting bracket aligned with the mounts on the axle, and the bolts screwed back in and torque up to the specified tightness, which you should check, but from memory is 60ft-lb, and use of a thread lock is optional. Brakes are subject to a lot of vibration, so it may be a good idea, though.

With the calliper secured, the brake pipes may be re-attached and fasted tight.

Part 2; Step 11 - Replacing Pads

The procedure for replacing the pads is covered in part one, following:

NOTE: As explained in Pt 1, I actually re-fitted the brake pads BEFORE I fitted the calliper back on the axle. This was mainly for ease of photography, but if you think you may find it easier, you can follow suit. However with the pads in the calliper and no disc between them, they can move about a little, or fall out from under the anti-rattle clips, and it can be a little 'tight' pushing the calliper over the disc.

Part 2; Step 12 - Bleeding the Brakes and Replacing Road Wheel

It is ESSENTIAL that you bleed through the brake system after overhauling any or all of the callipers. It is just as essential if you have merely disconnected a brake hose to allow a disc replacement. The process is covered in:-

But please note, that after a full calliper overhaul, the system may need a LOT of fluid and it is advisable to actually 'flush thru', and make sure that you get new fluid in the callipers, both to ensure that you have eradicated air-locks, but also to put 'new' fluid around those new seals, so that the seals will swell and seal properly. Remember comments earlier on the matter of solvents in the brake fluid for this purpose, old fluid will break down and those solvents may, after use, not be as effective.

Once the system has been flushed or bled through, the road wheel may be re-fitted, and the car lowered onto its wheels, as:-

AFTER a calliper overhaul, be aware that the brakes will take a little time to bed in and 'settle'; they may need re-bleeding, and you DO need to remove the road wheel and look for any indication of weepage or seal failure periodically until you are confident that the brakes have 'bedded in'.

Part 3 - Brake Disk - Removal & Replacement

Part 3; Step 1 - Remove Brake Pads from Calliper.

The first jobs in removing and replacing the Brake Disk, is to remove the brake pads from the calliper, as part 1, following the steps:

Part 3; Step 2 - Removing Calliper from Axle

The next job is to remove the Calliper from the axle, which is covered in Part 2, Following Steps:

However, if you are NOT overhauling the calliper, it is possible to save some time and effort by NOT uncoupling the brake lines, and not completely removing the calliper, but unbolting it, and leaving it 'supported' near it's mount, still attached to the brake-lines.

This would be good, as it saves having to bleed the system through afterwards, but you do need to be particularly careful that you dont damage or stress the brake lines by not removing them, or in the way or position you support the calliper while you ar working on the Hub.

Part 3; Step 2A - Alternative Removing Calliper, without disconnecting Brake Lines

First of all, CONSIDER comment in Part 2; Step 3 - Uncoupling the brake lines, about what kind of brake lines you have, then trace carefully th routing of pipe work from the calliper, before deciding whether to try and lift the calliper clear without disconnecting them.

Flex-pipes, as used at the front, will allow the calliper to be lifted clear of the disk more easily, BUT, you need to be able to support the calliper, and not leave it 'hanging' on those flex-pipes.

More rigid 'hard-hose, is less easily 'flexed', though provided it's not forced, and kinked, it CAN give a fair bit of movement, copper pipe more so, but be careful with copper that you don't 'work harden' it or crack it bending it back, when you put the calliper back!

So, give yourself some room, make sure that the hoses or pipes are loos of any guides, or clips or anything that will stress them when you move the calliper, and work out where and how you are going to support the calliper, whilst you are working on the Hub & Disk.

In the picture I think I've supported the calliper on a length of copper wire, between a mounting bolt hole and one of the upper coils of the spring, but however and whatever you attach it to, just make sure that it is strong enough and secure enough first.

Then follow instructions for, Part 2; Step 4 - Un-bolting the Calliper, but keep careful hold of the calliper, and keep it supported until you have it securely supported.

Part 3; Step 3 - Removing the Hub

The sequence for removing and overhauling the hubs, bearings and seals is detailed in Hubs Inspection, Maintenance & Overhaul, but, unless full overhaul is being undertaken to the hubs, some stages are unnecessary. However, given how many 'Common' stages there are, If you are renewing the brake disk, it is probably worth using the opportunity to at least inspect the hubs and wheel bearings, and if nothing more, a couple of quid on a new hub-seal could save a lot of hassle at a later date.

The steps given in the hubs article, to be followed then, are:-

Part 3; Step 4a - Removing & ABS Sensor ring, IF fitted.

On REAR brake disks, ABS equipped models have an ABS sensor ring inside the disk, a the rear of the hub, covering the heads of the dist retaining bolts, and this has to be removed before the disc can be undone from the hub. (Note; there is a sensor ring for the front brakes, but that is inside the swivel housing on the CV joint, and for a disc replacement need not be disturbed)

The ABS sensor ring is fastened to the brake disc by five M6 studs, with nyloc nuts situated in the gap between the brake disc and the hub flange. Ie, a typically 'awkward' little corner! They have to b diligently turned with a 10mm open ended spanner, and the nuts will probably be corroded onto the studs, so the studs will probably unwind out of the sensor ring, rather than the nuts unwinding off the stud! If so, the stud is too long to get out through the gap, so will stay hanging loose through the disc until you have beaten that off the hub!

Take note, because when you come to fit the new disc, IF you have nuts corroded on the studs, you either have to get the nut off the stud and refit it to the ring before you put the ring back on, renew th studs and the screws ('preferred' option), or you have to fiddle the studs through the disc before you put it on the hub, so that they are there to be screwed into the sensor ring after wards!

The ring is 'centred' on the hub on the same boss as the disc, and it's likely that it will be a tight fit and reluctant to come out. Before you wind the studs right out of the holes, or the nuts right off the end, having worked round all five studs, you can help ease the ring off its seating by using an old screwdriver or chisel to pry between the hub flange and the stud nut.

Work round each stud, using a 'LITTLE' pressure each time until it comes unstuck, then after winding the studs all the way out or the nuts all the way off, turn the hub disc side down and a little 'agitation' should see the ring fall out, use a rag or something soft to catch it in!

Part 3; Step 4b - Removing & Disc from hub.

The disk is bolted to the hub with five 14mm 'double-hex' headed bolts. That is, instead of having six sides, they are a twelve pointed star.

This bolt head form demands the us of a twelve point socket. It's NOT a fancy head form, it isn't a 'Torx' or 'Security' pattern or anything, its designed to exploit standard 12-point sockets, which instead of having six sides to bear snugly on the walls of a normal nut, has two hexagons superimposed on each other in a 12 point star, that will fit a nut two ways and bear on the corners.

These sockets are generally weaker than six sided ones, so the usual advice is to buy straight six sided sockets.

In THIS instance though (and I seem to recall I also came across it on a number of fasteners during the Dead, to RED! overhaul of Bert's V8) they are essential.

Reason for using 'double-hex' head fasteners is that the head can be smaller, so convenient where clearance is tight, but they can usually take a lot more torque than an 'internal' drive, like an allen screw.

These (& the nuts & bolts inside Bert's V8 that needed 12-point sockets), do need a heft torque to be applied, so if you have a set of six sided sockets or a 'cheap' set of twelve point sockets, I strongly advise a trip to thee motor factors for a set of 'reliable' quality 12-point sockets, a rail covering the range 10mm-17mm should be less than a tenner, and is usually thee most economical way to buy them.

The torque on these bolts is specified as 38ft-lb, which is not a HUGE torque, but, they should also be thread-locked, which mans that it will probably take a fair bit more than that to 'Crack' them out. It's certainly more than you'll be able to react holding onto the disc, so you'll probably have to use a Tommy bar across the wheel studs (suitably protected) to stop the hub twisting as you try and undo the nut.

As the hub is off the car, a 'tip' that was suggested to me, which I have to confess I have never tried, for cracking off brake disk bolts, is to bolt the hub back onto the road wheel with ALL the wheel nuts, then lay the wheel face down and stand on the tyre to hold the assembly still while you tackle the disc bolts...... I have absolutely NO idea whether it makes life any easier than a Tommy bar across a couple of the studs, but you may like to try it!

Once the bolts are removed, the disc SHOULD slid off the back of the hub, but chances are it wont, and will need a bit of persuasion before it drops off the boss in the middle.

You may have the notion of trying to 'jemmy' between the gap between the disc and the hub flange, but I found it awkward and couldn't get enough purchase or hold the hub hard enough to achieve anything, and you risk 'tilting' the disc on the boss making it jam harder. It MAY work if the disk isn't too tight, though and you work around carefully and evenly.

I used the age proven method, of resting the disc on four bricks, putting something sift underneath to catch the hub when it fell, and 'wamping'  the boss as hard as I could with a hammer, until the hub fell off!

If you elect to use this method, please be aware that IF one of the bricks falls over or cracks under more 'enthusiastic'... er, 'wamping', thn you could get hurt!

You should ALSO note that that boss ion the middle of the disk contains the hub bearing and the rebate for the hub seal. Significantly enthusiastic wamping MAY deform, damage or crack the hub, and even more 'considerate' wamping can peen over the metal making a hub seal replacement rather difficult!

I used a piece of steel plate over the boss centre to take the direct impact of the hammer blows, and spread the force as evenly across it as I could, and I worked around the boss to avoid it tilting and jamming. As soon as I had a gap, I 'eased off' and used lots of lighter blows, around the boss and it eventually dropped out of the middle of the disc.

As shown in the pic, I'm actually prising the hub-seal out, after bating it out of the disc.

Part 3; Step 5a - Fitting New Disc To Hub.

As supplied, a new disc has a course honed surface, and usually a smear of light grease storage protection. The course honed surface tends to be quite 'smooth' and it will take bit of use to se that machined finish 'roughed up' by the brake pads, and the disc 'bed in' and settle.

Some authorities advise cleaning the 'storage film' off a new disc with solvent before fitting up to prevent tit contaminating the brake pads, others advise the contrary and not risking contaminating the pads by using any kind of solvent to remove the storage film!

Personally I'm in the latter 'camp', discs are normally cast iron, which is porous, and using a solvent is as likely to dissolve and soak the grease into the metal of the disc as it is to remove it. I give them a hard 'wipe over' with a rag, and that is it.

The 'bedding in' of a new disc sees it a little less 'grippy' and during that 'bedding in' the small amount of lubrication offered by th storage grease is not significant, and use SHOULD get the brakes up to temperature sufficient to 'burn off' that storage film, very quickly and effectively.

Actually fitting the disc is a relatively simply matter, it slides over the hub-boss and bolts down with the five 'double-hex' headed bolts mentioned when we took it off.

However, there are a few cautions; If you check the factory service book or rave manual, or look in the Haynes manual, there is mention of measuring 'disc run out', which is basically making sure that the disc runs straight to the hub, and there is advice given for measuring it with a Dial Test Indicator. This is NOT something that is done on the factory floor during original assembly, the run-out presumed to be controlled by assurance of the tolerances of the piece parts. And If you are fitting a new disc, you should be able to rely pretty much on the same assurance and presume that a new disc will run true. If worried, though, See Part 1; Step 3 - Inspection of Pads, Pistons & Disk, but to be assured that the disc will mate up good and true, pay attention to cleaning up the mating faces and the centre of the hub-boss, before you try fitting the disc.

Having done so, you can lowed the disc over the hub boss, and a bit of 'wiggling' to get the disc sated comfortably is a good idea, then you can fit the disc bolts loose and 'dry' to line them up and pull them up and be sure of a good seat.

Then working around the pattern on 'opposites' remove a bolt in turn, add thread-lock, and tighten it up finger tight, before going over the pattern again, 'wrench tight', THEN, remember its a setting tool, not a big ratchet, go over the pattern a final time setting th bolts to the correct torque, which again you should check, but from memory is 38 ft-lb.

Unlike when you took the old disc off, this shouldn't be so tight that you cant hold the disc and hub while you apply that force, so you shouldn't need to brace it with a Tommy bar across the (protected) wheel studs or try 'bolted to wheel trick.

Part 3; Step 5b - Re-Fitting ABS Sensor ring to disc, IF  fitted.

The ABS sensor ring should be thoroughly cleaned and inspected prior to re-fitment.

In my case, failure of the hub seal had seen it covered in grease, to which was stuck a lot of  brake dust, and where the pad backing plate had been running against the metal of the disc, metal filings.

Before removal, I HAD seen an intermittent ABS warning, and that magnetic material clocking the sensor ring was probably a big part of it, but regular brake pads contain sintered metals that can also 'fool' the sensor, so it IS worth cleaning thoroughly.

The Haynes suggests also paying attention for any sign of marking on the rotor, as well as to the studs behind.

In my case the studs had wound out with the nuts, and attempts to remove the nuts from the studs were not happy. 'good form' would have been to replace the studs and nuts altogether.

I pondered making up my own studs from M6 'uni-thread' rod, as the thread is the same on both ends, and the lack of the small portion of plain 'shank' wouldn't have been too worrying. However, I ultimately decided to re-use the old studs. This meant that I had to fiddle them into the holes in the disc BEFORE I fitted the disc, but that was fairly easily done using some spare M6 nuts on the ends in place of th ABS ring to hold them in place while I fitted up the disc. NOT ideal, but often a real world necessity. HOWEVER, because I was using them as a 'bolt', effectively, and they are a 'low torque' fastening, normally secured the other end by the nylock in the nut, I DID use a thread-locking solution to make sure they stay put!

I also, before fitting the ABS ring, gave the heads of the disc bolts a lights smear of cuppa-slip against any moisture and consequent corrosion, once they were hidden behind it, and similarly gave the inner edge of the ABS ring, where it centres on the hub boss a light smear. NOTE: 'light Smear' means a little dab on your finger wiped around so it 'wets' the surface, NOT great gloops of the stuff so it looks like it has been touched by the hand of Midas!0

Part 3; Step 6 - Putting it all back together!

Is all detailed in the other sections and in  Hubs Inspection, Maintenance & Overhaul, but to provide the sequence, it's as follows:-

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Foot-Notes

Splitting Callipers

On some vehicles, the callipers are 'strictly' not serviceable; they don't offer overhaul kits, and the length of the piston and the clearance between the two halves is such that you cant actually pull the pistons. Hold one in and pump the other out, and it clamps up hard against the 'in' slug before the bottom comes out! The only way to get the pistons out, is to 'split' the calliper.

I HAVE attempted the overhaul of such callipers before, and discovered that the lack of 'approved' seal or over-haul kits NEEDN'T be too great an impediment, and it is possible to buy individual seals from specialist 'industrial' bearing and seal stockists, of the right size and shape AND grade of rubber, including the 'joint' seal, for most applications.

BUT! Get it wrong, and have a seal fail on you, and you COULD have some very difficult explanations to make as to why you tried messing about with a part that the manufacturer advised SHOULD have been scrapped! So I don't generally advise such things!

But it does mean that you DO undo the wrong bolts on your calliper, or if you find that the pistons are so corroded that they will not come out of of the cylinders and the only way to get at them is to crack the calliper apart and get a bit brutal with it, all may NOT be lost.

However, for an old Land-Rover or Range Rover, unless your circumstances demand it, brand new callipers aren't horrendously expensive, and 'good' second hand callipers are often pretty easy to come by, and that would probably be the 'safer' way to sort the job, and less hassle that trying to track down suitable seals.

My experience splitting 'non serviceable' callipers actually stems from my MG Metro - 'Q-Car. And with a little 'inside info' was able to split and rebuild its 'non serviceable' callipers, and include a couple of 'tweeks' to make them a bit more powerful!

It was something that the AP lads did quite a bit, for their own hot-road cars or budding club racers, and quit commonly, they would build 'special' callipers and master cylinders, with bigger pistons in them to go into 'blue-print' racers. Built from 'stock' components, they looked like catalogue parts.... and the scrutineers wouldn't question them! MORE than a few such 'specials' found their way into 'production' consignments, in 'tagged' packaging, and were built into show-room cars, that conveniently happened to be shipped to the 'dealer-sport' operations, or be pulled off the line for the factory race teams, to compete in 'standard production' or 'Group-N' classes!

Which is all a little bit of a diversion, but, there are ways and means, and IF you have something you are trying to 'hop-up' to be a little bit more potent, without throwing lots of obvious 'performance' parts at it, or if you have something rather more exotic than a Land-Rover you are trying to restore, and are suffering trying to track down suitable parts, callipers CAN be split, and even really BAD cases where the internal ports are all furred up or the cylinders badly worn or scored, it is possible that they can be refurbished.

I seem to recall, a 1960's Massaratti posing something rather difficult in it's braking department, and a master cylinder that couldn't be replaced. A 'substitute' would have spoiled the car's 'concourse' originality, and the original was so badly worn and corroded that new seals and pistons just wouldn't work, but some 'precision' machining, was able to bore out the old cylinder, and shrink fit a thin steel 'liner', salvaging the part and maintaining the originality; NOT cheap, not cheap AT ALL!, but possible if really necessary!

 

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