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back brakes grabbing harder than front


JStumpalump150
11-28-2009, 08:14 PM
its been a while since i have posted something on here but i have quite a big problem. when i hit the brakes my back brakes grab way harder than the front and it causes the backs to lock up. how do i fix this? i already bled the front brakes in hopes of fixing the problem but no luck. what should i do next? oh, and the front brakes and rotors have less than 3000 miles on them, the rear pads and drums have 9,000 or so.

534BC
11-29-2009, 09:43 AM
Try to verify that ther fronts are working and have enough travel. The trouble seems to be in the front and not the back, right?

JStumpalump150
11-29-2009, 05:45 PM
well it turns out there was a bunch of black gunk in the master cylinder and fluid reservoir that was the problem, took it apart and washed it and now it works although im not sure what that black gunk was

JStumpalump150
12-03-2009, 10:24 AM
well that was a temporary fix i guess cuz they are doing the exact same thing again. i read in a bunch of places that aftermarket shoes dont fit exactly how they should and only the ends would grab the drum causing it to lock up the back wheels, so people have been shaving the ends down a bit to make the whole pad touch and not just the ends. has anyone heard of this before and does it work? at this point im desperate cuz its winter and when snow hits this is going to be a disaster, i cant have my back brakes doing all the work cuz ill crash and die so please chime in with any tips you have lol

J-Ri
12-03-2009, 06:48 PM
I've done probably hundreds of rear brake jobs on Cavaliers (and cars that share the exact same design) with aftermarket (Raybestos) shoes with no problems at all. You could give shaving them down a shot, but first remove the drums and remove all the brake dust with brake cleaner and then reassemble. For some reason, that makes the brakes grab sometimes.

I don't see how less contact would make them grab... plus if that were true, then you couldn't machine a drum or that would always happen unless you used new drums.

Also make sure the parking brake isn't partially engaged, having the parking lever pushing the shoes out takes out the free play and makes the shoes grab as soon as you touch the brake.

JStumpalump150
12-03-2009, 09:03 PM
well its the leading edge i guess that will dig into the drum instead of letting the whole shoe gently grab, but i have no idea about this stuff, thats just what i read on a bunch of forums. and the brakes were cleaned last weekend when i was trouble shooting this the first time :/

J-Ri
12-04-2009, 06:43 PM
I missed that you said you had 9k miles on these shoes, any edge would have worn away by now.

What about the parking brake lever? I would pull them back apart and check it, maybe even remove the bars (the ones that go from shoe to shoe, that overlaps the parking brake lever on the one side) and take it for a test drive. After adjusting my brakes I accidentally left the parking brake on just a click or two and I locked up the rear brakes pulling out of the shop, barely touching the pedal.

Was the friction material at any time contaminated with brake fluid? I've seen leaking gear oil do that on a RWD vehicle.

If you can spare the cash, maybe even buy a new set of shoes (I strongly reccomend Raybestos Professional Grade) and see if that fixes it. Either you fix the problem or you have a set the next time the brakes need doing.

That black goo you had in the master cylinder would make me wonder if maybe the proportioning valves might be stuck, but yours has a split-diagonal system so both would have had to stick at the same time or just one would be appling hard. I believe yours has a combination valve (combination valve is part of that), on mine it's right under the master cylinder or next to it or behind it. I know for sure if you follow the lines from the master cylinder you'll run into it eventually :). If nothing else fixes it, remove the valve and clean it out. If you get any goo out of it, I'd replace it, cleaning it out you may miss some. Brakes are one of the systems you shouldn't hope something will work, don't want some that may have held on to stick a valve on ice :) After that, bleed the brakes and drive it.

Otherwise maybe the front brakes aren't doing enough, making it seem as if the rear are applying too hard.

JStumpalump150
12-05-2009, 11:57 AM
well i ended up taking it to the stealership they charged me $50 to "adjust them" but now they work, wish i could have figured it out myself but i could not wait cuz it snowed and it was getting scary to drive. but thanks for the help!

Jmrec100
12-23-2009, 10:19 PM
What kind of adjustment did they do? Sounds like the parking brake adjustment?

RacerE7773
12-24-2009, 03:32 AM
:sarcasmsign:My LR brake in my 2000 cav (good riddance) locked up the same way and it was the adjuster needed looked at as did the parking brake.

JStumpalump150
12-24-2009, 08:47 PM
i dont know what they did but it worked till i sold the car lol.

RahX
12-25-2009, 05:11 AM
This is going to sound crazy but I promise it has fixed nearly 100% of the cavys I've had with the same problem- the rear brakes are OVER adjusted. They need to be adjusted DOWN. The easiest way to do this is pull the rear wheels/drums and loosen the adjuster and then put it all back together. With the rear wheels off of the ground, adjust them up slowly from the back while spinning the wheel until you hear the the shoes just start to scrape the drum then stop. That should be about perfect. And anything that is in the drum that is not dust, water (depending on the weather) or lube on the backing plate needs to be corrected.

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