Brake woes, front disc failure at low miles and other problems

Pinkythelabrat

A2OC Donor
I had used the mintex disks for about 50k and agree to that ratio - two sets of disks and four sets of pads over the period. I did get a bit of a lip on the first set towards the end (maybe 30k in) but not as bad as yours look.

Im using ATE disks now but only because they were cheap (from SteveA2), looked nice and came with LOW DUST pads. Which make a lovely difference to my front alloys.


Sent from my iPhone using Tapatalk
 

audifan

A2OC Donor
Had several A4s in the past that had a brake drying function that effectively pulsed the front and rear discs calipers to dry them out, Pads and discs were changed every 10000 as they were worn out. Never noticed the brakes getting any hotter because of this.
 

Howey

Member
I had a 98 passat did 50k on the pads but discs started to get tatty after 8 years so changed them when half worn, 10K sounds like harsh breaking or a V8 automatic to me?

Well no you wouldnt as the brakes would be working as intended
 

philward

A2OC Donor
Are the pads free? Do you often jet wash the wheels?
Never jet wash, can't say about the pads. Had to use a wrecking bar on them, stuck behind the hard expanded outer ring on the discs.

Edit: I always lubricate them with copper grease to keep the moving for as long as possible.

Edit2: I'll get some better pictures so you can see the problem better.
 

KekseKaempfer

A2OC Donor
Check that your wheels are not buckled. I had a constant issue with warping disks and it was only when I span and checked the wheels that i noticed one of them was out of true. Unfortunately we sold the car before we could verify that this was the actual reason. It'd be a good thing to check regardless.

Chris
 

philward

A2OC Donor
Check that your wheels are not buckled. I had a constant issue with warping disks and it was only when I span and checked the wheels that i noticed one of them was out of true. Unfortunately we sold the car before we could verify that this was the actual reason. It'd be a good thing to check regardless.

Chris
Will do, thanks or the tip.
 

philward

A2OC Donor
Things that weren't wrong:
- Wheels weren't warped / buckled
- Brake fluid looked good (I don't have a moisture detector)
- Caliper pins are in good order

Things that were wrong:
- Pistons were corroded, one caliper weeping brake fluid
- Rust build up compressing caliper pin rubber bushes

Things that may have been wrong:
- Hard pad soft disc combination (this would be a manufacturer problem as I have used the same brand of pad and disc for many years)

Result with less than 10k miles
- Rust build up on outer edge off disc where the pad does not contact, this chips off with a hammer.
- A further 10mm of hardened discolored disc with concentric grooving which is thicker then the normal worn portion. This does not chip off.
- Normally worn disc before more defects on the inner edge.

IMG_6444.JPG
 
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philward

A2OC Donor
What I have done:
- New pistons
- New seals including pin bushes
- Fitted ATE brand discs and pads

IMG_6449.JPG


Unless anybody recognises the cause of this failure, with 100% confidence, all I can do now is drive and see what develops, or hopefully not, over the next 10k miles. Thank you all for your advice and comments.
 

audifan

A2OC Donor
While the discs were off it is worth checking the face of the hub is clean, rust free and running true. If it has a run out then the disc will not run flat inside the caliper, this could cause early wear and disc warping. it can even produce a braking imbalance between the 2 front wheels. Wheel bearings can also effect the path the disc takes in relation to the caliper.
 

cheechy

A2OC Donor
While the discs were off it is worth checking the face of the hub is clean, rust free and running true. If it has a run out then the disc will not run flat inside the caliper, this could cause early wear and disc warping. it can even produce a braking imbalance between the 2 front wheels. Wheel bearings can also effect the path the disc takes in relation to the caliper.
I can definitely testify to the wheel bearing point - I had uneven wear on one side due to this but the bearing wasn't quite showing it was on the way out. This was the first sign and I didn't pick this up so was left scratching my head around reasons for the uneven disc wear, after I'd replaced the caliper seals etc.
 

Merlin3046

Member
Following this thread with keen interest. I have a similar disc consumption rate, with the pulsed braking returning about 6 months after replacing discs and pads (Brembo), becoming unbearable after 12 months. Next time it'll be new callipers too, I reckon. And this is with new wheel bearings and all other suspension joints. Mind you, I haven't checked the wheels. Should probably do that first.
 

kp 115

A2OC Donor
Following this thread with keen interest. I have a similar disc consumption rate, with the pulsed braking returning about 6 months after replacing discs and pads (Brembo), becoming unbearable after 12 months. Next time it'll be new callipers too, I reckon. And this is with new wheel bearings and all other suspension joints. Mind you, I haven't checked the wheels. Should probably do that first.
Hi Merlin,
My brembo’s were fine until I had to drive through deep water !
There after no clean disc surface & judder increasing each month.
Hth
Keith
 

philward

A2OC Donor
Do your wheels expose the front discs, seems very strange like those discs look like they have been on for ages!

What make hasnt been lasting??
Sorry I misread your question, I’ve been fitting Pagid discs and pads.
 

Howey

Member
Thats even more confusing as most pagid discs have a coating that seem to protect the non contact area of the discs really well and are indeed good quality, i dont know why you have been having so much trouble!
I fitted Bosch discs in January as the discs the car came with were quite tarnished and tatty making the brake pedal feel a touch "soft" on initial application, will update if they do the same as i have standard 15" wheels also.
A product that is fantastic for all things rubber is rubber grease, its red and i use it on tons of stuff for example slide pins on brake calipers
 

Rusty911

A2OC Donor
I've been watching this thread with some consternation as have never worn through a set of discs since I started driving in 1988. This includes several thousand miles of towing. Naturally cars have arrived with worn or corroded pads / discs and they are attended to, but after that, no, they just run and run. I should say perhaps that I live in a hilly area and few of my miles are of the relaxed motorway sort.

So ... I do use 'decent' brands, so TPS economy brakes (which are fantastic), Pagid, Ferodo or Brembo. Usually whatever I can get at the time.

I have a feeling that nearly all of the above issues are down to calipers not releasing fully. If you're not getting a good 20-30K out of a set of pads on a manual car, let alone discs, something's horribly wrong. This may be mechanical, or in some cases, dare I say, driving style. Let's assume the former as obviously we're all perfect drivers on here.

A few things: if a front caliper is happy, there should be no friction at all when the car is jacked up and the wheel turned. The design of the piston seal is such that it slightly grips the piston and retracts it a fraction once the brake pedal is released. The slider rubbers do the same. The sliders should allow the caliper to slide easily enough that if you retract the piston a fraction by levering the caliper over a touch, you should be able to slide the caliper by hand (no leverage).

The pads should be able to slide by hand within the caliper: if you need to lever them, they are too tight.

Common faults on the actual caliper:

i) Corrosion (rust) up behind the caliper bellow seal, pressing the bellows hard onto the piston. No amount of levering piston back and forth will deal with this.

ii) Ditto for the main piston seal (the square section one).

iii) The piston itself is corroded.

All three will leave a piston that is unable to self-retract. Therefore, when you come to a halt you have a very hot disc with pads clamped hard onto it in one place. This means one area is cooling at a completely different rate to the rest, leading to warped discs and a pulsing when the brakes are applied, especially lightly.*

Cure for all three is the same: get a drip tray, remove the caliper but leave it connected. Pump the brakes gently until you feel the pedal suddenly go soft. Gently press the pedal all the way down and wedge it down with a bit of wood between that and the driver's seat: no more brake fluid will come out. Remove the piston from the caliper, working it out from the bellows. Remove the bellows carefully by collapsing it inwards. Some designs are held in with an spring clip. Use a hook tool or tiny flat screwdriver, lift out the square section piston seal. Clean seal and bellows: almost always they'll be fine to go again.

Use a Dremel with wire brush and plenty of WD40, clean out the inevitably corroded bellows and piston seal channels. They'll almost always release a ton of rust: keep going until they are bright again.

1500 grit the piston using WD40 and polish. Not a huge issue if the last 5mm or so is a bit pitted, but replace if the pitting encroaches upon the seal.

Give the inside of the caliper a good spring clean: ideally brake cleaner, but WD40 will do, you're cleaning it all with some clean rag / paper towel anyway. Make sure it's clean, dry and debris free: use a torch to make sure.

I should say, it's very satisfying at this stage: rust has all gone, inside of caliper is lovely and clean and you have a little row of seals / piston all ready to go back in.

Lollop red rubber grease into the piston seal channel and refit the seal. Refit the bellows, again on a bed of red grease. You should see both will sit right into the channels now.

Now the tricky bit, red grease the piston and try to get one 'side' into the bellows and then try to work the other half over the piston. This is the worst part of the whole job. I've got various little blunt hooky tools I use to ease the bellows over the piston. This done the piston can be eased into place in the caliper. You may have to wiggle it a bit but it will start to slide in eventually. If you've done all of this O.K., the air pressure will try to push the piston right back out: that's how free it should be.

EDIT: The caliper slides on pins that run on rubber inserts. If the caliper doesn't move freely, carefully remove the slider rubbers (they can be eased out by pulling in a circular action). Clean these in and out (or replace) but importantly, use a loose fitting drill bit to clean the hole in the casting of rust, debris, old grease etc. Refit the slider rubbers with plenty of red grease, check the pins slide smoothly and without binding up. Often rust in the hole can force the rubber into the pin, restricting movement.

O.K. , that's the piston area, there's another area of potential issue: the pads. With the pads and anti-squeal shims out, file up any area of caliper that contacts either shim or pad. Corrosion often builds up under the shims unseen, clamping the pads in place. Reassemble using Copper Ease or similar under the shims to slow future corrosion. Do a quick reassembly and try sliding the pads: you should be able to move them with a finger: so not rattling loose, but an easy slide. If they are tight, gently file the very ends where they contact the anti-squeal shims. Refit with some anti-seize of some sort (Copper for cast steel / iron, white for aluminium).

Once re-assembled, bleed the brakes. Be aware that if you've fitted just new pads, any disc ridges on inner and outer edges should be nipped off with flap disc in a grinder or even with a file. You may find that if you use new pads on used discs (perfectly acceptable assuming discs will go again) it may take a few miles for the brake pedal to finally firm up. This is because the give you are feeling through the pedal is often the new pads flexing slightly as they try to match to the disc.

As is usually the case with my little interjections, note the total cost of my caliper clinic is in the region of £5, assuming discs and pads going again. A couple of Dremel wire brushes, a dab of copper grease, a splash of brake fluid and some elbow grease (priceless). I've had a little practice I'll admit, but could probably do the front end of a car in roughly 90 mins all in. Allow a couple of relaxed evenings or a weekend morning if you've not done it before and you'll be fine.

Key thing is to make sure the road-wheel can spin perfectly freely: ideally just after someone has stomped on the brakes with the engine running. That's the greatest test and replicates actual driving.

*On trackdays / racing, you never apply the handbrake when parking in the paddocks post session: you always put the car in gear or chock the wheels. This helps to prevent warping.
 
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Rusty911

A2OC Donor
I should probably add an extra thought: if the car is a daily driver, always make sure you can undo the brake bleed nipple before starting any work requiring a brake bleed. Yes, you can sometimes twist the caliper around to get the hose near the top and crack that, but that's real red-neck get you home stuff.

Ultimately though, if the nipple shears off before you start any work, it's no big deal: you have time to think it through and get organised. The car stills drives. If it shears later on, well that's a whole heap of pain if you're due into work the next morning ... :eek:
 

Joga

A2OC Donor
I've been watching this thread with some consternation as have never worn through a set of discs since I started driving in 1988. This includes several thousand miles of towing. Naturally cars have arrived with worn or corroded pads / discs and they are attended to, but after that, no, they just run and run. I should say perhaps that I live in a hilly area and few of my miles are of the relaxed motorway sort.

So ... I do use 'decent' brands, so TPS economy brakes (which are fantastic), Pagid, Ferodo or Brembo. Usually whatever I can get at the time.

I have a feeling that nearly all of the above issues are down to calipers not releasing fully. If you're not getting a good 20-30K out of a set of pads on a manual car, let alone discs, something's horribly wrong. This may be mechanical, or in some cases, dare I say, driving style. Let's assume the former as obviously we're all perfect drivers on here.

A few things: if a front caliper is happy, there should be no friction at all when the car is jacked up and the wheel turned. The design of the piston seal is such that it slightly grips the piston and retracts it a fraction once the brake pedal is released. The slider rubbers do the same. The sliders should allow the caliper to slide easily enough that if you retract the piston a fraction by levering the caliper over a touch, you should be able to slide the caliper by hand (no leverage).

The pads should be able to slide by hand within the caliper: if you need to lever them, they are too tight.

Common faults on the actual caliper:

i) Corrosion (rust) up behind the caliper bellow seal, pressing the bellows hard onto the piston. No amount of levering piston back and forth will deal with this.

ii) Ditto for the main piston seal (the square section one).

iii) The piston itself is corroded.

All three will leave a piston that is unable to self-retract. Therefore, when you come to a halt you have a very hot disc with pads clamped hard onto it in one place. This means one area is cooling at a completely different rate to the rest, leading to warped discs and a pulsing when the brakes are applied, especially lightly.*

Cure for all three is the same: get a drip tray, remove the caliper but leave it connected. Pump the brakes gently until you feel the pedal suddenly go soft. Gently press the pedal all the way down and wedge it down with a bit of wood between that and the driver's seat: no more brake fluid will come out. Remove the piston from the caliper, working it out from the bellows. Remove the bellows carefully by collapsing it inwards. Some designs are held in with an spring clip. Use a hook tool or tiny flat screwdriver, lift out the square section piston seal. Clean seal and bellows: almost always they'll be fine to go again.

Use a Dremel with wire brush and plenty of WD40, clean out the inevitably corroded bellows and piston seal channels. They'll almost always release a ton of rust: keep going until they are bright again.

1500 grit the piston using WD40 and polish. Not a huge issue if the last 5mm or so is a bit pitted, but replace if the pitting encroaches upon the seal.

Give the inside of the caliper a good spring clean: ideally brake cleaner, but WD40 will do, you're cleaning it all with some clean rag / paper towel anyway. Make sure it's clean, dry and debris free: use a torch to make sure.

I should say, it's very satisfying at this stage: rust has all gone, inside of caliper is lovely and clean and you have a little row of seals / piston all ready to go back in.

Lollop red rubber grease into the piston seal channel and refit the seal. Refit the bellows, again on a bed of red grease. You should see both will sit right into the channels now.

Now the tricky bit, red grease the piston and try to get one 'side' into the bellows and then try to work the other half over the piston. This is the worst part of the whole job. I've got various little blunt hooky tools I use to ease the bellows over the piston. This done the piston can be eased into place in the caliper. You may have to wiggle it a bit but it will start to slide in eventually. If you've done all of this O.K., the air pressure will try to push the piston right back out: that's how free it should be.

O.K. , that's the piston area, there's another area of potential issue: the pads. With the pads and anti-squeal shims out, file up any area of caliper that contacts either shim or pad. Corrosion often builds up under the shims unseen, clamping the pads in place. Reassemble using Copper Ease or similar under the shims to slow future corrosion. Do a quick reassembly and try sliding the pads: you should be able to move them with a finger: so not rattling loose, but an easy slide. If they are tight, gently file the very ends where they contact the anti-squeal shims. Refit with some anti-seize of some sort (Copper for cast steel / iron, white for aluminium).

Once re-assembled, bleed the brakes. Be aware that if you've fitted just new pads, any disc ridges on inner and outer edges should be nipped off with flap disc in a grinder or even with a file. You may find that if you use new pads on used discs (perfectly acceptable assuming discs will go again) it may take a few miles for the brake pedal to finally firm up. This is because the give you are feeling through the pedal is often the new pads flexing slightly as they try to match to the disc.

As is usually the case with my little interjections, note the total cost of my caliper clinic is in the region of £5, assuming discs and pads going again. A couple of Dremel wire brushes, a dab of copper grease, a splash of brake fluid and some elbow grease (priceless). I've had a little practice I'll admit, but could probably do the front end of a car in roughly 90 mins all in. Allow a couple of relaxed evenings or a weekend morning if you've not done it before and you'll be fine.

Key thing is to make sure the road-wheel can spin perfectly freely: ideally just after someone has stomped on the brakes with the engine running. That's the greatest test and replicates actual driving.

*On trackdays / racing, you never apply the handbrake when parking in the paddocks post session: you always put the car in gear or chock the wheels. This helps to prevent warping.
Excellent write up of caliper and pad roles in brake bindning problem, I can just fully agree based on my observations and reflections.
As other have indicated here and there, I also see one more potential problem source, the disc "position" related to the caliper.
If the new disc slightly wobbles due to uneven or uncleaned mounting surface on the hub, or wobbles due to a low quality wheel bearing with too much play, pads will be slightly touching the disc causing heat build up which fully in line with @Rusty911 text can cause more warping in it self.
 
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