Seized caliper, or something worse?

brakes
#1

This is probably a simple issue, but I’ve not had it before. The rear brake pads on the left side quickly ground down to the carriers and scored the disc. On the right, it looks like the pads aren’t even making contact with the entire disc, just the inner part (i.e., more toward the center hub). What could cause this? I always figured the hydraulic pressure would equalize the side to side application, but clearly something is wrong. Or perhaps the caliper on the right is partially frozen, making the left do all the work. Anyone BTDT? Recommendations on cures?

#2

You need to tell us what type of vehicle you’re talking about before anyone can help.

Tester

#3

The vehicle make/model would help, but if your disc brakes are not wearing evenly it is likely that you have at least one bad caliper. I would replace the calipers and discs on both sides and then keep an eye on it. I would also replace the flexible line to the caliper at the same time.

#4

do you do your own brake jobs?

it sounds to me like the last time the rears were done the caliper slide pins weren’t greased. (but you havent given any pertinent vehicle info, yr, mileage since last brake job, etc.)

typically if the brakes are wearing unevenly it is because the caliper and slides aren’t “equalizing” the pressure on the inner and outer pads. the caliper slide pins (or rails depending on your model car) need maintenance too.

#5

1998 Audi A8 Quattro. Yes, I do the brake jobs myself. All four corners were done in June 2006, and the car has run about 15,000 miles since then. The front brakes are holding out fine.

#6

“typically if the brakes are wearing unevenly it is because the caliper and slides aren’t “equalizing” the pressure on the inner and outer pads. the caliper slide pins (or rails depending on your model car) need maintenance too.”

clean and grease the slide pins and or rails. they sell a specific slide pin grease for this at the auto part store. you dont need alot, but cleaning them, and regreasing is important.

and make sure you dont contaminate the pads with the grease.

#7

Check that the parking brake cable is not hanging up.

#8

one more issue. (although probably not related since you have uneven wear on both R and L sides)

when you retract the caliper piston you must first clean all the residue from around the flexible rubber bellows that seals the piston. these bellows only fold in one specific way, and any crud in there can jam the piston from acting properly. if you look at the piston as you push it in (however you do it is up to you) you will see that a fully extended piston will fold the rubber bellows in two to three times. it is an amazing feat of rubber molding to see it work! if the bellows aren’t folded in properly (due to crud in there) they can jam, and not “relax” when you let up on the pedal. this will cause premature brake wear on the side with a sticky boot (since the brake pad never fully lets go of the rotor).

#9

another thought.

you can tell which (piston or slide pin) is sticking by which side of the pad is wearing. if it is wearing on the caliper side of the pad the caliper piston is sticking, and if it is wearing on the opposite side, the caliper slide pins are sticking.

#10

Does VW/audi use that funky “sliding caliper” design, or do the calipers have pistons on both sides of the disc?

#11

When ever I do a brake job I remove the pins…take them down cellar…and use the wire wheel on my grinder to get them nice and clean and smooth. Then I grease them up with some good grease…(I have a tub of Amalie that I’ve been using for the last 5 years). I’ve found that just regreasing the pins without cleaning them first is almost as bad as NOT greasing them.