Uneven brake wear?

[tevake]

I am about to open up the pistons to replace the rubber parts. but am wondering what may have caused such uneven wear on both rear calipers. the outer pads seem to have worn twice as fast as the inner pads. What would cause this?? Didn't happen on the fronts. This is a 1980 SC
Thanks Richard

[Flieger]

Sticky pistons. The outer one is the only one moving and doing the work. Very common.

[T77911S]

+1

i had a stuck piston on each caliper.
bad break lines can do it too. always a good reason to upgrade to braided.


my conclusion to this after recently dealing with another car that had stuck pistons is that the breaks are not getting used hard enough. i have noticed this with my driving. i have been letting off the gas a lot sooner when coming up to stop lights and then lightly touching the breaks to slow down. because of this, i believe one piston may do all the work in stopping the car, then the other gets stuck from lack of use. so now i make it a point to lay on the breaks pretty hard at least once a day, which is not a problem.

a freind told me he has nearly 100k on his breaks, i told him he may be saving money now, but when it comes to putting pads on, he may really pay due to the extra labor in a caliper rebuild or just in getting the pistons unstuck to get new pads in. i spent 3 hours on a volvo that should have taken less than 30 minutes.

[tevake]

You are both right on about the stuck pistons. I went on yesterday trying to dissasemble
the calipers for seal replacement. and have been unable to move some of the pistons
with air pressure. I did all four corners at one time to get on with the job. So now it seems that I will have to reassemble and get fluid back into the lines to be able to free up the pistons.
Any one have an easier way to break them loose?

[burgermeister]

You can use 100+ psi air pressure. Also remove dust boots and squirt lubricant of some sort into the bore. Push out a bit, push back in with pliers, back out with air ... they'll pop out eventually.

Note: Safety glasses & wood block in caliper are a MUST - when they pop out, it's like a gunshot. If you have a body part in the way, be prepared to not get it back ...

[Flieger]

I found it was easier to buy some restored calipers from Eric Shea at www.pmbperformance.com and then sell him my cores to re-coup some of the cost.

[tevake]

With the calipers reinstalled on the car W/O the discs, and with the help of my 12 YO son Alex to do the peddle work for me. The pistons did free up . It took quite a few trips around the car to get them all moving well.

Burger Meister, I was thinking about your words of caution as the 2x2" piece of wood splintered between the pistons. While I was working on the other side . Yikes there is lots of power there!!

Flieger, Those are some slick looking calipers you have there, is that ceramic coating on them. The travel time plus cost of shipping made going on with this here seem the way to go for me
Thanks for the helpful input
Richard

[Flieger]

They are clear anodized Aluminum S calipers. He now uses a frosted anodizing more like RSR Fuchs. For M calipers he does silver cad with a quick flash of yellow for the factory look.

[Eric_Shea]

cost of shipping

$10.20 Flat Rate boxes

(thanks Max)

[Flieger]

BTW, I got new the Zimmermanns and Porterfield R4S's all around working well on the canyon twisties. Fresh ATE Blue, no dust shields, and nice, shiny S calipers.

[Eric_Shea]

Happy? Working well?

[Flieger]

Yep, bedded them in as you said (interesting smell) and they look good- nice and "burnished" but still have some "cross-hatching" marks on the rotors. They stop the car very well. Pedal is firm but easy to modulate. They do not pull anymore or squeak occasionally. I am happy.