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Brake issue

1469 Views 15 Replies 6 Participants Last post by  djstrachan
So, I've been fighting a shudder/vibration at highway speeds for some time now. Have had the tires re-balanced 3X, CABs replaced and suspension inspected...nothing!

Today, I took her out for a "spirited" drive and applied the bakes aggressively at high speed. . WHile I had thought the brakes were a little "rough" feeling, after a 20 minute session, the brakes literally were "grinding" under heavy braking and there was definitely a shudder in the front, felt through the wheel and floor boards when applying moderate to hard braking force. THe grinding and shudder began at speeds that seem to correspond with the vibration I have been getting.

When the brakes were hot and I applied force at higher speeds, it almost sounded like a semi truck with it's jake brake on!! WTF?!!!

Pads and rotors were all replaced 6k miles ago. Zimmerman rotors, Textar pads.

I have had the brakes apart and can push the pistons in by hand. The pins wer polished only a few weeks ago (I did not lube them).

Pads and rotors all appear to be wearing smoothly and evenly.

So...what could be causing this?

Thanks guys
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What kind of shape are your wheel bearings in ?
Ya know, this is something we haven't talked much about before but could be a possible issue. His car only has 55k miles or so on it, it would be odd for one to be bad, but I know the OP is grasping for any last straw he can get right now.

Bob, I told djstrachan via PM that being able to push the caliper in by hand is very odd, wouldn't you agree? I always have to use a clamp or tool for the job? :dunno:
What kind of shape are your wheel bearings in ?
What happens when you stand hard on the brake pedal when the car isn't moving? Maybe you have a bad master cylinder.
Wow....ya got me thinking in another direction now....do you think the piston could be rattling around inside its bore, setting up some kind of weird harmonic ?
Bob, I told djstrachan via PM that being able to push the caliper in by hand is very odd, wouldn't you agree? I always have to use a clamp or tool for the job? :dunno:
You guys are scaring me now.

Perhaps I am just incredibly strong?!! Nope, that's not it.

Honestly, on all 4 calipers, I can push the pistons back using my hands. They dont' go easily but by keeping pressure on, they smoothly go back.

Bob, the bearings are tight when doing the 12/6 test. With the brakes removed, all I hear is a smooth "swoosh" sound when turning by hand.

Considering the obviousness of the brake noise/feel, I may at least be on the track to solve this annoying vibration.

I'll take the brakes off again tomorrow and see if after the hard driving today, something looks off.

Is there anything else I can do to test the bearings? I've had "issues" for awhile now and before I replaced all the pads and rotors (though not this bad).
Wow....ya got me thinking in another direction now....do you think the piston could be rattling around inside its bore, setting up some kind of weird harmonic ?
With steady force all my pistons can be pushed back into my calipers by hand. Happens on my other cars too.

Go around corners hard to listen to bearings making more grinding noise if they are bad as a test for bad bearings.
Thansk,

I'll give that a shot. Didn't hear anything today but was focusing on the brakes.
With steady force all my pistons can be pushed back into my calipers by hand. Happens on my other cars too.

Go around corners hard to listen to bearings making more grinding noise if they are bad as a test for bad bearings.
Update...

Took front wheels off and looked everything over again. Pad and rotor wear is smooth and even. NO evidence of run out when spinning rotors and no play or noise when putting pressure top to bottom .

Re-checked torque on carrier bolts - they were about a 1/4 turn away from 81ft lbs.

Took it for a test drive and...vibration still there starting at 65mph. Smooths out (sometimes) around 80-85 and vibrates again above that.

Still grinding when braking moderate to hard at higher speeds. Feel it slightly in the steering wheel and pedal but mostly seems to be coming through the firewall/floorboards.

I'm thinking the vibration and grinding are related, at least I hope so.

Listened for bearing noise under hard cornering but heard/felt nothing.

One interesting little tidbit...the "donuts" on the new Meyle CABs keep coming out of their place and I find them hanging on the arm. I have to push them back in. It feels as if they are greasy as though the dish soap I used to put the bushings on has never dried and makes then slippery.

This happened with one of the previous Meyle CABs as well. I was wondering...if the actual CAB is in the same condition, it could be slipping on the control arm. Pretty weird that the soapy water would not have dried though.:dunno:
Did you use a very dilute solution of dishwashing soap?

Hope you didn't mix it too strong.
I thought I mixed it thin enough. After replacing the "donuts" for the 5th time, I decided last night to put the Lemfoerder CABs back on. THe Meyle's required a 2 jaw puller and impact gun to remove so they were on there solid. So much for the slippery soap theory.

Only went for one drive but would say a noticeable reduction in vibration to the point it may not be an issue. ONly had time for a few hard brakings but hardly noticed any "grinding" or vibration under hard braking.

I'll do more experimenting and report back but so far, very pleased wiht how the car feels with the OE bushings. Not so much unneccessary road "noise" yet I did not notice any reduction in handling.
Did you use a very dilute solution of dishwashing soap?

Hope you didn't mix it too strong.
Urgent help!!

UPDATE!

Still fighting vibration but seems to be mostly from the rear. Maybe being transferred to front by driveline:dunno:

Took calipers off and noticed something that looks wrong to me. The pins are clean (polished) and move smoothly in boots. BUT...the rubber bellows on the piston is not extended with the piston. Instead, it appears fully retracted on both calipers.

This does not appear correct to me. What problems would this cause? I am assuming this would prevent the piston from retracting when the brake pedal is released?

It looks to me as though the pads are wearing evenly. There are only 6k miles on these rotors and pads (Zimmerman rotors, pagid pads). Experiencing high speed pulsing and "grinding" from rear brakes. Corrosion appears to be creeping in on the edges of the pad contact area likely causing the grinding noise. Could this be related to the piston bellows?

Picture attached.

Attachments

The caliper in the first pic looks bad and like it is leaking a little.
just the photo and some of the brake grease making it look wet. It's dry as a bone.

I moved the piston further out (applied brakes) and the boot is attached properly just further back than on some pistons I have seen. It moves back in when the piston is compressed with a c-clamp.

I'll have to look elsewhere.
The caliper in the first pic looks bad and like it is leaking a little.
Wow! Those are really corroded up. I'm thinking you should get a couple repair kits and rebuild them, but be prepared to replace them with remanufactured calipers just in case you get the piston out and find the interior or piston corroded too.

I am rebuilding a rear caliper, possibly today, and I'm going to make a video while I do it to share with everyone. I'll need some time to edit it and get it out on YouTube. I've already done the other three and found all of those boots damaged, but inside things were nice and clean. This is actually quite simple to do with a little care and patience.
Jeff,

I think they look worse than they are. They use Calcium Chloride on the roads here in the winter and it eats metal parts. The actual piston (other than brake grease) is not corroded and moves in and out very smoothly. The pins are polished and smooth and the boots seem to be in good shape.

The rotor and pad wear appears to be even all around. The only thing I noticed is some "creeping" corrosion from the edges of the pad contact area on the rotors and some small grooves in the outer surface of the passenger rotor. The pads were all smooth though perhaps "glazed somewhat.

I will keep an open mind however, and am considering rebuilt calipers (either myself or buying them) if symptoms persist. I have new rear rotors (Ate) but don't want to install them 1) because the current ones are only 6k miles old and 2) don't want to ruin them if it is a caliper problem.

Brakes shouldn't make a grinding noise when braking at highway speed. Something isn't right. No sign of noise or play in the bearings.

I'll watch for your caliper re-build video. Saw one on Youtube,...didn't look that hard.
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