RebuiltRunner

For those who might know? What causes caliper lock-up? I was thinking of driving up to Chicago and needed an inspection sticker. While I was there I decided to get the brakes looked at. I was shown how my right front was wearing very unevenly (not just more than the left, the bottom of the right shoe was worn more than the top). I was told by the guys at Brake Specialists here in Austin that it was due to caliper lock-up. I asked him what causes that, he said it was due to brake dust.
I got my truck after it'd been hit and I wondered if the frame naot being completely straight could have something to do with it?
They quoted me $364 dollars for labor and a "caliper kit", pads brake fluid flush, rotation (after I thought he said it didn't need it), caliper adjustment...

I'm sure I can do the pads myself, but what of the adjusting the calipers? Should a novice leave that to the guys in the black in grey shirts?

Mohamed

Okay, so he looked at your rear brakes (you mentioned shoes) and he said it was because of your front caliper locking up? First off I have never heard of a term of "caliper lock-up", second if the bottom of the shoe is worn more than the top, more than likely the assembly has something incorrectly installed (like a return spring or possibly the shoe hold down spring) or your wheel cylinder maybe going bad on one side. It is quite possible you have an axle out of shape in the rear, but it doesn't affect braking wear in shoes, in a dual-servo brake drum assembly, the wheel cylinder pushes (with it's small piston) on the top of the shoes and the action of the wheel movement, moves the shoes to press on the side of the drum. It's kinda hard to explain I know, but get a second opinion.

Oh and calipers aren't adjustable, there is a square cut seal in the middle of the bore that sort of serves as an adjustment when the pads start wearing, and help resess the piston to where it needs to be when the pads wear. Only shoe clearance on drum assembles are adjustable.

RebuiltRunner

good info, the rear brakes aren't the issue this is just the right front. I do think I''ll run and have the break checked somewhere else....


thanks

amusement

Mohammed is right. there is no such thing as caliper lock-up.
I also agree with Mohammed's idea of the return spring not properly installed.

The front CV axel being bent ... I would disagree. Front CV axel bent would make noise at highway or less speed.

Things I would consider when taking it in:

The overall thinkness and groves of the rotor.
The shape of the front caliper. Warped? Cracked?
brake pad return spring(s) .. bent .. broken .. missing

Last note: You would have very squeeky brakes if there was too much brake dust on the rotor and the brake shield. Some organic pads make the rotor very shiny.

A good brake mechanic will rough up the rotor a little to help the new pads were in.

My 2 cents.

RebuiltRunner

I just got the estimate out of the truck. this is what that shop said it needed:

"Resurface/replace rotors, isntall new brake hardware, rebuild calipers , bleed system..." $160.66

the parts are:
brake fluid $16.23 (?!?)
brake pads (bendix) $76.53 ?!?!
Caliper Kit $48.84
brake hrdwr $34.86

I still plan to take it somewhere else - as soon as I can figure out how to replace my broken wheel lock key.

So if it is a caliper rebuild is that something a novice can handle? At the least, I'm going to buy as much of the parts myself. That price for pads just seems kind crazy to me w/o being an upgrade of some kind.

Mohamed

Broken wheel lock key? bummer, but any tire shop should be able to take out the key lock lug, they have special stuff in the shop for that. If you want to, you can go ahead and just buy another key lock set. It sometimes ends up being cheaper than buying another key, and quicker (prices at alot of shops are around $8-$15) price of a key can be $10.

Rebuilding a caliper is not hard, but I say...nah , ya we did it in class, take off the caliper, gotta remove the dust boot, then there is a clip that hold the boot in (sometimes you gotta remove the clip first then the boot), then place a small block of wood near the otherside of the piston bore and with shop air in the brake line hole, release air, MAKE SURE YOUR FINGERS ARE NOT IN THE WAY OF THE CALIPER PISTON. Remove square cut seal. If it's badly scored inside (shouldn't be) not good to machining the bore (in fact it's very bad practice to do so), just get a new remanufactored caliper at this point. If the housing is okay, put in new square cut seal, lube the bore with special grease in the kit, insert piston into bore (work around the piston with your fingers, while pushing it in, it has to go all the way in), put on new dust boot (or clip depending on the way it's setup), attach caliper to brake line, attach pads, (gravity bleed that caliper first, by cracking bleeder screw and when fluid oozes out, close) then, bleed car in normal method (included the caliper worked on again). But I think it's just easier to swap a remanufactored caliper in and DON'T throw away the old one, those have a core charge on them...

Are you sure you're calipers are bad? The only way they are bad is if they are leaking, sticking, well you get the idea...

RebuiltRunner

Errrr, that sounds likd something I DON'T want to do. Somehow, I figured changing out the whole caliper would be easier.

I'm not sure whether it's the caliper or not. That's why I'm going to take it to another shop. Although, given the way that pad was worn, it does seem like it would be something with the caliper.

I've actually already had some locks taken off be a shop without a key. I think I'm about to give up on the locks completely. If I get another set now, this will be the 3rd since I got the triuck last year. Tan mucho trouble.

Thanks for the input, gents.

hypnotoad

easy way to tell if the caliper is frozen: after driving, put your hand on the wheel - if it's hot the caliper is stuck!

More practical method:
remove caliper from the wheel (leave rotor in place) and use a C-clamp to attempt to drive the cylinder back into the bore - only checking for the ability to move it slightly, don't drive it all the way back in! If it moves, caliper is fine. If not, replace the whole thing. If the cause of junk in the bore (causing it to freeze) is a scored wall then a reman kit won't help. They're not that expensive and the peace of mind is worth it.

You can even get a "loaded" caliper with pads already in it, but that only saves you a minute or two so shop for price.

BTW - the standard recommendation is to replace both calipers together. I've never done that and never had a problem.

Mohamed

Oh ya forgot about that point.