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brake when wet. grind and shake?


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Okay, so I've noticed a very odd problem on my '02 OBW (75k)...

 

Occasionally, not always, when i brake moderately to heavy in the heavy rain I get a grinding type noise (does not sound like metal on metal), and a pretty bad steering wheel shake. The harder the braking, the louder and more violent the shaking.

 

When I brake in the dry I get an occasional shake, kinda like a 'warped' rotor, but no noise, and not as near as bad of a wheel shake.

 

The rotors and pads are pretty new (oem), maybe 5-7k old. Rotors are smooth, I don't see any odd patches. I recently pulled the calipers off, and check and re-lubed the slide pins.

 

Any thoughts? Could this be suspension related at all?

 

Thanks for the help..

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I think one of your new rotors is out of round, I have bought new ones before and had one be bad. You can get one new one from Auto Zone for around 28.00 dollars. Try it on the right front, if that dont fix it put the one you took off on the front left.

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Hmm, cheapest Autozone lists is ~40, but that's a good idea. I have the old rotors I took off, maybe I can get them turned for cheaper and then test.

 

I torque the lugs to ~68-70 ft-lbs, star pattern. Tires have about 15k on them. I took apart the calipers and relubed the pins, they seemed okay, not sloppy. What else can I check on them?

 

ABS kicking in> I don't think so, but I hadn't thought of that.. It's kinda like a roar/grind. I don't brake very hard so it shouldn't have seen any wheel lock-up. Next time it rains I'll have to pull the ABS fuse.

 

Thanks for the help!

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Here's another thought that may be contributing to your grabby brakes. An 02 has now had the same brake fluid in its system for 5 years, if it has never been flushed out and replaced with new fluid. Three years is the usual life span of brake fluid before a flush and replacement, otherwise water starts the rusting cycle inside the brake calipers and starts to seize up the pistons. Yours may be at that state, and are starting to grab at odd times. One way to tell (unless you've been following the factory recommendations and already have changed it at least once) is to look at the colour of the fluid in the reservoir. If its not clear, but rusty to black in appearance, then its been long overdue for flushing. If you suspect that sticking pistons might be your problem, you can pop them out of the calipers one at a time to check them, and if not badly scored, you might be able to clean them and the caliper bores up with 0000 steel wool. But then, maybe this isn't the cause of your problem at all. Just a thought. Good Luck!

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Thanks for everyone's comments, they're much appreciated.

 

Okay, so it rained again last night, and I got the same behaviour. Pulled the ABS fuses and the same thing happened.

 

Now, oddly enough I did notice that the shake/grind was only under moderate braking. When I really put my foot down the shake and the grind went away and everything was smooth... not sure what that means!

 

gbhrps, I flushed the brake fluid at 60k, (15k ago), maybe I still have air in one of the lines? I have checked the rotors after normal use to see if one was hotter than the other, but they seemed okay. Might be a good idea to check the pistons though, thanks for the suggestion.

 

Any other thoughts? I know of a good local Subie shop, might be time to drop by!

 

Thanks again!

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