Front Brakes - Help

[stevedohc2b]

Take them back and exchange for a different set if new.

All so check dia of each piston as some are larger ie abs

Stephen

Edited September 14, 2014 by stevedohc2b

[Richard Grove]

This afternoon we tried bleeding the caliper with it off the vehicle holding up as high as possible. Definitely no air in system but still no improvement. We are working on one caliper only with other side blocked off at the master cylinder with a bleed screw.

 

Have just removed caliper from car and stripped it down on bench. All seals are good and piston measures 53.9mm i.e smaller non ABS version.

 

Can't think of anything else so will try some new calipers.

 

Thanks for all the suggestions.

 

Richard

[Grim]

did you retract the piston fully into the caliper before bleeding? that can sometimes trap a little air in if you don't.

Otherwise, is there a fluid leak allowing air to be drawn in?

[megadodo]

Why can I see the piston seal in the first picture? If there is a pad in there I shouldn't be able to see it! You have fitted both pads and that picture is just to show the spring position?

[Grim]

or is it the caliper for 260mm discs?

[Longboarder]

The rear edge of the piston is visible on my pics as well and my brakes work fine. I think this is correct and correctly assembled. As you can see from the pic below the rearmost central tang which grips the inner wall of the piston is positioned so the rear part of the piston will be off the rear edge of the pad. Odd but as intended I guess.

 

Nigel

[stevedohc2b]

Are the disc the right thickness?

[megadodo]

I'm going to have to go and have a look at mine now! It may be because the caliper piston is painted orange that I "think" there's an issue with pad position.

[johnlrichardson]

The metal part of the pad does not seem to be fitting properly onto the caliper. and the disc seems a lot thicker on one side

 

Think wrong calipers or disks

 

HTH jon

[richardm6994]

Well I now know the problem must be the calipers themselves. We clamped the flexi hoses just before they enter the caliper and brake pedal is solid.

 

When you did this test, was the engine running / servo functioning? If it wasn't, I would try again with the engine running to definatley eliminate or identify the servo being the cause of your problems because from what you've said and done, the servo is what my mind keeps coming back (assuming everything has been fitted correctly).

 

 

If it's not the servo, then it's a real head scratcher.......if the calipers leaked, you'd see fluid on the floor....you say they are bled properly so the only other thing that would cause those results at the caliper end would be a broken / cracked caliper body....but I've never heard of that before.....

Edited September 15, 2014 by steamer

[Guest zerorace]

Just a thought when you had the caliper of how did you stop the piston moving when you bled the air out?

With the caliper of if you had a ratchet type G clamp holding the piston in and had hard peddle it would indicate nothing wrong with the caliper and point to the assembly of the rest of the components .

Just my thoughts

Edited September 15, 2014 by zerorace

[richyb66]

Given that you've got a pair of new calipers and one new master cylinder, the chances of having 2 faulty calipers seems highly unlikely and I can't see them being completely the wrong calipers for the car.

 

I'm not certain either that blocking off the ports on the master cylinder and getting a decent pedal proves anything if there's 2 seperate pistons in the cylinder. With 3 ports blocked off, either the front or rear circuit could be faulty but you'd still get a decent pedal.

 

With the front ports blocked off and the rear brakes connected you also get a decent pedal, but it doesn't prove that the front circuit isn't faulty.

 

I think I'd be looking at a collapsed seal in the master cylinder or some other fault and I'd be swapping that first or pull it to bits and check the seals.

[Richard Grove]

Thanks again for all the ideas.

 

We have ruled out the servo and the rear brakes as when the 2 front outlets on the master cylinder are blocked we get a nice firm pedal with engine off and engine running. We know the servo vacuum is working OK because you can feel the brake pedal move down when the engine is started.

 

So it must be the calipers themselves. I bought them off e-bay 6 months ago and I confess they were quite cheap. They look fine and we are convinced we have the right pads discs etc. When we tested the caliper off the car/hub we used the brake disc itself to clamp onto. As you press the brake pedal it feels normal as the caliper clamps on the disc but as you keep pushing it look like the caliper is twisting on the guide pins and never seems to lock solid. We think the calipers must be machined wrong so not pulling square.

 

Any ways we decided rather than get another set of sierra calipers we would upgrade to Willwood powerlite calipers which were ordered this afternoon.

 

Richard

Edited September 15, 2014 by Richard Grove

[Guest zerorace]

Which kit have you ordered I would just like a look

 

thanks.

Edited September 16, 2014 by zerorace

[Richard Grove]

http://www.rallydesign.co.uk/product_info.php?products_id=10508

 

Went for these with drilled & grooved discs and Powerlite 4-Pot - Smart Pads - BP10.

 

I already have this set up on my 2B and it works fine with no servo, so should be good on the new 2B which we are building for my son.