Very squeaky brakes after new pads

[S1_RS]

The "mechanism" which draws back the piston/pads is actually built into the shape of the seals within the caliper. The seals are not dead flat against the pistons and so distort when pressure is applied, when released they return to their normal shape which in turn draws the piston back slightly.

http://www.eng-tips.com/viewthread.cfm?qid=284644

[XG332]

I had a really bad squeal that turned out to be the edge of the st shield had been bent in a little and touched the back of the disc when braking.

[chryslerben]

S1_RS said:

The "mechanism" which draws back the piston/pads is actually built into the shape of the seals within the caliper. The seals are not dead flat against the pistons and so distort when pressure is applied, when released they return to their normal shape which in turn draws the piston back slightly.

http://www.eng-tips.com/viewthread.cfm?qid=284644

This ^^^^^

[S8QUATTRO]

Dino D said:

Ozzie Osmond said:

Manufacturers put considerable efffort into engineering brake materials which don't squeal. Aftermarket parts are not so rigorously tested.

That's the same bs story Honda tried to tell me when changing pads on a Jazz for stupid money.
The pads and calipers were branded Nisin, not Honda. The motor factors sold me the same Nisin pads for a fraction of the price. I don't think any car maker makes the brake pads they use in the cars they make.

Car manufacturers dont make brake pads. They are produced by friction companies and designed in conjuction with the car companies based on the requirement of the models, the same goes for shocks, springs, discs, wipers, headlights etc.. The factory fit pads in most cases will have a more expensive friction material. This is normally a higher quality and hopefully means the customer of the new car wont have any issues with the brakes. The parts you buy aftermarket are made to a standard. Only a few brands are like for like factory fit product such as some Textar part numbers on some VAG, Merc, BMW.

Good topic though

[chryslerben]

S8QUATTRO said:

Car manufacturers dont make brake pads. They are produced by friction companies and designed in conjuction with the car companies based on the requirement of the models, the same goes for shocks, springs, discs, wipers, headlights etc.. The factory fit pads in most cases will have a more expensive friction material. This is normally a higher quality and hopefully means the customer of the new car wont have any issues with the brakes. The parts you buy aftermarket are made to a standard. Only a few brands are like for like factory fit product such as some Textar part numbers on some VAG, Merc, BMW.

Good topic though

True on both counts

[maniac0796]

S1_RS said:

The "mechanism" which draws back the piston/pads is actually built into the shape of the seals within the caliper. The seals are not dead flat against the pistons and so distort when pressure is applied, when released they return to their normal shape which in turn draws the piston back slightly.

http://www.eng-tips.com/viewthread.cfm?qid=284644

Yes, rotation of the seal helps to pull the piston back, as does run out from the disc.

As for brake squeal, that is high friction between the pad and disc, which causes the pad to vibrate against the piston or caliper. Rubber, copper slip, adheisive backings can help damped this squeal. Grease on the end of the pads simply helps to lubricate them so they can slide easily in the carriers.

What you have to be careful of is not mistaking squeal with grinding or rubbing.

I would say take the car back to the garage, or have a crack at it yourself.

[P I Staker]

chryslerben said:

P I Staker said:

The run out in the disc is what pushes the pad away, if you had a perfectly manufactured disc with no run out you would have this problem.

ETA: AT the garage I worked at and at college we always put copper grease on the back of pads. Its common practice.

Can I just stop you there mate your obviously still at college and copper grease on pad backings stopping squeal is bull, 99% off squeal you will experience on customers vehicles will be caused by friction lining contact with disc normally through either mismatch, pad glaze or just cheap ste pads.

Fair enough.

[NHK244V]

chryslerben said:

I'm not talking inches or even mm buddy I'm talking 10ths to 100ths of mm. Ask any race driver why they tap the brake pedal after a hard corner?

You may or may not believe what I say buy I've been doing this a long time commercially and on proffesionally on track

yep because of pad knock off, twas a huge problem for rally drivers back in the 70's with the rear calipers that had no mechanical handbrake to hold the pad close to the disc, still is to an extent especialy with fully floating axles as the bearings have more play in them than the normal type bearings.

[PhillipM]

Not really, that why we run floating discs, anti-knockback springs and residual pressure valves, don't have to worry about it any more, haven't for a long time.

[Gafferjim]

penryar said:

Personally I'd take the pads out, file a small chamfer onto the leading edge of the pad, copper slip on the backing plate and refit. Should remove all squeal until they've bedded in fully.

This is the correct way to stop pad squeal.

[Ozzie Osmond]

S8QUATTRO said:

Car manufacturers dont make brake pads. They are produced by friction companies and designed in conjuction with the car companies based on the requirement of the models, the same goes for shocks, springs, discs, wipers, headlights etc..

That's exactly the point. OEM means original equipment on the car and specifically engineered for the car. Just because something looks the same doesnm't mean it IS the same and certainly doesn't mean it's better. There's a strong case to be made for buying original parts for safety-critical applications.

As for someone who said disc brakes need a tap of the pedal before you get to a corner because that's what all the racing drivers do - it's absolute twaddle. Your steel disc brakes are quite happy left alone until you need them. But then if you're Ayrton Senna and need your carbon disc/pad brakes at a constant 700 degrees .....

[airads]

Hi I have been around cars for the last 40 years and more rebuilding and making them and in all that time when it came to squealing brakes I have put a finger tip of copper slip on the dices face just in front of the pads this then lubricates the pads and stops them from squealing it is burnt off when the pads are bedded in and it will not contaminate the pads and make them u.s

[Otispunkmeyer]

BlueMR2 said:

I found with new pads that often alot of dust comes off and a good wash with a hose on the disks and pads until it flows clear water off the wheel usually stopped squeaking for a fair while.

Worth a try as its free and braking performance usually improved a little after as well.

Coincidently I did wash the car on Friday and while the squeaking stopped I nearly had a heart attack when the pedal seemed to do nothing. Probably got some degreaser on the discs I imagine.

It had calmed down a lot now, done close to 1000 miles now. I guess with the light squeaking on the move they are not releasing cleanly.

I'll just take it back to them when I have time ( free time is scarce). It does still squeal like a piggy and goes through phases of high pitched squeal, rough grating sound. I guess I am
Wearing through layers on the pad. As I said, probably dirty cheap pads. Buy cheap but twice eh!

Thanks for all the input though!

Edited by Otispunkmeyer on Sunday 18th March 13:33