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Sierra Brakes
mistergrumpy - 15/8/10 at 12:31 PM

Just after some advice. I've always had issued with my brakes since I built the car and they'r still going on. At the moment I've a kind of squeak going on on the front nearside brake. Its once every revolution of the wheel. I've changed the bearings and its still there so I wondered if I had a warped disc. I went to swap the fronts around earlier and I noticed that the brake piston seal looks like it may be trapped a little on one edge or at least not uniform like the rest of it so I've pressed the brake pedal and found that I can fully depress it to the bulkhead and the piston only moves a few mm outwards. This can't be right I'm guessing.
Any ideas before I start the job tomorrow. I've to leave for work in a bit so won't be able to start it now

Mark Allanson - 15/8/10 at 12:43 PM

Possibly rear shoe adjusters not working properly - yes really!

When you apply the brakes, the shoes move out to meet the drum and should stay really close for the next application, if they don't the springs pull the shoes back onto the cylinder and push fluid back into the system and the only place it can go is into the front calipers causing the pads to drag. Would also explain you small movement in the front piston as the effort is being used in opening the rear shoes.

mistergrumpy - 15/8/10 at 12:50 PM

Sorry. Calipers all round with a Fiesta MC and each front caliper having its own dedicated line and one to the rear splitting into two.

Mark Allanson - 15/8/10 at 12:56 PM

Bugger - It took me ages to type that too!

interestedparty - 15/8/10 at 01:37 PM

quote:
Originally posted by Mark Allanson
Bugger - It took me ages to type that too!


Good point, though, and it's one I will take note of, never know when it might crop up, so time to type not wasted

Mix - 15/8/10 at 04:16 PM

Hi

Depressing the brake pedal will only result in a very small movement of the calliper pistons - probably no more than 2mm. In normal use the pads are positioned a few thou off the discs by the elasticity in the seals. Don't expect to see a large movement.

Regards Mick

mistergrumpy - 15/8/10 at 10:59 PM

Ah right. I had it in my head that the piston would come right out. So its right in what it's doing then?

Mix - 16/8/10 at 04:07 PM

Hi

It may be that the dust seal, (I assume that's the one you think may be nipped), is stopping the piston retracting as it normally would when the brake is released, resulting in light contact between pad and disc and generating the squeak.

Regards Mick

mistergrumpy - 16/8/10 at 10:23 PM

Bang on Sorted now. Thanks all.

silky16v - 17/8/10 at 03:14 PM

quote:
Originally posted by mistergrumpy
Bang on Sorted now. Thanks all.


what was it?

mistergrumpy - 17/8/10 at 06:02 PM

Dust seal trapped slightly on one side stopping the piston fully retracting.