Brake Pedal Travel

[TomL]

Hi NevSpit,

 

It does still sound like a classic case of air in the system.  Anyway, I'm glad to hear you've sorted it out.  Always good when you see some results from your work.

 

Regards,

 

Tom 

[David Mather]

On 23/01/2017 at 4:00 PM, derekskill said:

This may be is a bit long-winded, please bear with me. I changed my brake calipers before Christmas and have had problems since with brake pedal travel. On the first push of the pedal, the travel was too much but they did bite and have a solid "feel" to the pedal. Give the pedal another push and it was spot on, however the next time the brakes were used it was the same again, too much travel. I tried bleeding the brakes with a vacuum bleeder; I found that it was drawing air in around the bleed nipple and need a smear of silicone grease around the nipple to stop it. I then tried a standard one-way bleed valve, got over adventurous and clicked the brake valve out of position. While putting this right I decided to replace the rear drums, there was a good degree of ovality. Success there, handbrake fine but still the dreaded excess travel. I've tried checking the wheel bearings and leaving the pedal under pressure overnight but no joy.

So today I thought I'd try a different approach, have a look and see if there was anything obvious. The first thing that I noticed after taking the wheel off was that the pads were clear of the disc, half a millimetre maybe? Pumping the pedal while watching the pads, I could see the pistons easing back. Taking the pads out one at a time, I've pumped the pedal, nice and easy, to move the piston in and out, to get a bit of fluid on the bores and further in to the seals and it has worked, we now have a fully solid pedal and the brakes are superb, problem solved at last. All that grief and it ended up taking an hour to sort...

A few thoughts though...  I wondered if anyone has come across this before? Perhaps the calipers had been assembled with very little lubricant on and the seals were rolling instead of sliding  in the bores? Could this be another reason why leaving the pedal under pressure works for some, lubricating a dry seal where it contacts the bore? I made the big mistake of getting stuck on one line of approach. My apologies for the length of this but I did want to pass it on and any comments would be interesting.

Thanks for this post.... exactly the same with mine (GT6) after fitting new calipers. The inner disc pad on both sides was loose in the caliper. Followed your same steps and problem solved in less than an hour.

Was going to start the re-bleeding all over again unless a little forum research. No apologies required for the length of your post. Perfect info. For me at least.

Cheers.

David.

[daverclasper]

Thanks a lot for that info. Changing my pads soon on Vit.

Dave

[Gully]

I've had the same issue with Pistons pulling back ever since I replaced my front calipers late last year. I'd put it down to not replacing the pads (they had little wear on them), but all the symptoms are as derekskill and David Mather have described - they creep back a little once the pedal has been released to leave a distinct gap pad to disc. Will have a crack at that fix at the weekend. Out of interest, what did you find the best method to push each piston back after extending it?

Thanks,

Gully

[Anglefire]

I suspect I’ve had a bit of this- but use seems to have sorted it out. Though I must adjust the handbrake on Saturday as I think the rear shoes have bedded in now too. 

[Andrew]

Hi all

i had exactly the same problem.  Bought two new callipers for my Herald from the club shop last year.  After fitting I could only  get a solid pedal after pumping.  The usual cause of this is adjustment on the rear.  The theory for this is that as you pump the first time the shoes expand and the second pump the shoes contact the drum.  Then when left for a few seconds the return springs pull them back to the starting position and the whole process starts again. So the fix was to clap,each flex hose all four at once. One by one taking a clamp off. After removing both rear clamps my pedal had a long travel.  This then lead to a fault at the front.  I noticed there was a cap between the pads and the disc.  So I removed both pads on side at a time, got an assistant to press the pedal until the pistons were exposed by about 1/2 inch pushed them back in replaced the pads and a short travel on the pedal was returned.  Cause of all this the seals in the callipers were pulling the pistons back in.

regards

Andrew

[Pete Lewis]

Simplest way to return the piston is a lever with something strong with pad of ply or whatever as its surprisingly easy to dig a mark into The disc face

 

Always check the HB cable is not holding the shoes open or rear adjustment is a waste of time  once set you, neve have to touch it again

Thats remove the cable clevis   lock the adjust up fully ,  adjust cable to just fit the clevis. Back off adjuster 4 clicks to free the wheel

unless you have self adjusters  but similar if the cable holds the shoes open the self adjuster cannot work as it never returns to off.

[Gully]

Success! Removed each pad in turn yesterday, pumped each piston out, gave the seals a squirt of brake cleaner, pushed them back and lo and behold my pedal travel is shortened back to how it was before the calipers were replaced. Thanks for the tips!

Gully