I have a weird problem where the car I recently purchased will vibrate from the right side while braking. I lifted the car and pulled each wheel to test the wheel bearings and there is no play. The rear shocks are new, front shocks are good, car is aligned, and wheels are balanced. It feels like my brake caliper or rotor is loose causing the vibration (is that even possible?) I don't have any metallic noises and don't know what it could be. Sometimes it is smooth and quiet, other times it vibrates (mostly once the brakes warm up but maybe I haven' noticed it cold) any ideas? I would think bad rotors are obvious all the tIme

 

I forgot to say this is a 1996 850 and the previous owner replaced the rear calipers

 

Sounds like the typical rear brake rotor being too thin issue.. Check the thickness and if its below the spec replace it..

 

The term "typical" makes me happy. I didn't notice significant steering wheel vibrations and I do think it was coming from the rear. Hopefully that is the correct diagnosis but I will buy a tool to measure. This car is new to me and I am still learning the problems. Also when I have the rear end up, only the passenger side wheel locks when I have the parking brake on. This will be a good time to adjust the driver's side parking brake cable. Thanks!

 

Mine has done it twice in the 17 years that ive owned it... well 430K miles..

It is an annoying humm vibration.. If they are not too thin you can get them cut..
Any machine shop would cut them fro like $10

 

I just looked at the service history and it says the rear rotors and calipers were replaced/serviced 3,000 miles and 5 months ago. Is it possible for them to get thin/warped so quickly? Also when I purchased the car, the rear shocks needed replacing and the right rear shock mount was loosely attached to the shock and moving around a few mm. After repairing this and having a quiet car I noticed the vibrations during braking. Maybe that caused premature rotor failure? I'll buy a measuring caliper after work today and see what I'm dealing with. Perhaps the shop never even replaced the rotors but charged for them, or they cut them instead of replace.

 

Either that or maybe the mechanic didn't actually "replace" the rear rotors, but just turned them instead and now they are too thin??

 

Maybe the rotors had glazing issues at one point before you bought it?

 

Or ... they found someone with really cheap rotors in price and quality to make a better profit and they have warped in three months

 

I finally got around to measuring the rotor with a caliper. This caliper might not be completely accurate since it is also measuring the thin area that does not come in contact with the pad. This area feels nearly even with the area that contacts the pad. I have attached photos. Does anything look wrong? What else should I check? A few things I noticed:

1.) The tire that came with the car had a flat spot. Perhaps the caliper froze and burned the tire? I'm not sure how this could relate to anything.

2.) The rear shock was loosely mounted, or the shock mount was blown on this side in the rear. Could this suspension play cause the rotor to warp after 3k miles?

I'm out of ideas. I turned the rotor several times and took measurements at 5 points. The numbers don't look that different to me.














What is glazing, and how would a history of that cause vibrating now? What causes it and how is it corrected?
Thanks

 

warped rotors l guess.mine did the same.l replaced the rotors and vibrations stopped.u can barely see a warped rotor.changing mine solved the problem

 

Glazing is when the rotor gets over heated and creates smooth spots on the rotor. under breaking smooth to rough, smooth to rough is what causes the humming
Which it looks like yours is from that first picture.

Looks like you should be ok to get them cut at least once more I believe the minimum thickness is 8.25..

But for the cost of cutting them, and possibly going to thin... you might as well just replace both rear rotors and pads.. you will notice the difference right away.

Plus grease up all those pivot points and slide pins

 

Last pic in post #11 of this thread; upper brake pad retaining pin appears to be backing out; not installed completely.

Also why is everyone assuming the rear rotors are causing the vibration? Fronts are more likely to warp and cause vibration under braking.

 

Nice eyes gdog! I imagine everyone assumed I checked the obvious

I will hit that in with a hammer and hope that's all. It's hard to believe a shop would do all that work and not push the pin in all the way.