Seized caliper pistons
 

Anyone else come across this, I've had AP 4 pot brakes on the car from the day I had it, originally they were installed on my STi2 wagon, last year braking efficiency started to suffer, I changed pads and nothing improved, investigation revealed that the inner pair of pistons only were seized in the caliper block, freed up they were fine until about 5 months ago when again efficiency suffered, looked like the discs were dead and pads close to the metal so I rebuilt new discs onto the bells and got some DS2500 pads to go on, in doing this work again found the inner pistons were seized, freed up and all ok for three weeks when seized again, stripped and rebuilt them complete this time, no signs of corrosion damage etc so I'm sort of puzzled, since the last rebuild they have been fine and have to say the DS2500 pads suit my driving style to the ground.

I don't use the brakes alot under normal driving conditions but the car is used every day.

thoughts anyone ?

bob

Hi Bob,

Are they road calipers i.e. with dust seals etc.

Have you spoken to AP or an AP agent about them?

I've been very happy with service and advice from BG Developments (http://www.bgdevelopments.co.uk/). Give them a ring?

You don't want brake problems on a Scooby and certainly not a Bob Rawle tuned one ;-)

Best regards,

Ian

I wouldnt recommend DS2500s with your sort of performance Bob! I would regard them as fast road only. Can recommend Pagid RS29s. However what the root cause of the piston seizing is another matter. Have you changed the seals? They suffer heat stress too and can perish, maybe yours are just starting to go. Any sign of dirt ingress? Fluid leak maybe? Echo the call into AP.....

Mark

Thanks for the replies, no there was no sign of any ingress or corrosion, they were just "stuck", took a deal of force to move them, seals look ok as well. Cleaned everything up and still ok now back together.

Went for the DS2500's as they seemed a good compromise, most of my miles are road and I intend to sprint it not track it so not that essential to go any further, any advice is welcome though so I'll bear the Pagids in mind for when I change.

So far they seem fine even when braking from very high mph down, no fade or judder but I have not given them repeated heavy stick.

I was going to shout up AP but thought some input here would be useful first.

Wheels are Oz Super T's shod with Dunlop Super Sport Race 215-45-17's. And very good these tyres are in all but standing water even though they are race construction (but dot legal).

cheers

bob

Few months ago I asked about Wilwood superlight 6 pot brakes as they haven't dust seals and someone in Nasioc mentioned that changing to ATE super blue brake fluid solved his problems with partially seized pistons after years of use without piston-seal changing, I can't remeber though why and how.
JIM

Thanks Jim, I put in Motul RBF600 fluid when I rebuilt, maybe that has something to contribute.

bob