Getting a vibration from light to medium braking at speeds. Gets progressively worse after hard use. Back to normal after cool down period. Hard braking; there's little to no vibration.

Hope you guys can help me single out what this might be.

a) warped rotors
b) bushings
c) pad build up

Additional info:
Suspension's making a lot of squeeky noise, mild clunking at slow speeds over uneven surface. Suspect the lower arm bushings and strut tower bushings are out. Noises came shortly after coil overs/swaybars/links went in. At first, noise noticed after hard driving, now it's all the time. Susp mods came before the brakes but noises cont. to worsen after brakes went in. No vibration on stock brakes but noises had started.

Upgraded brakes are BBK F/R 15". Fronts are used (good condition no cracks/grooves barely worn), rear is new. Followed break in procedures for rears from manual. Both sets went on same time. Had little or no vibration when first installed. Haven't used these brakes anywhere near what may be experienced at a track. Level of vibration has gotten worse over time.

Car feels fine other than that, stable at high speeds and hard cornering.

thanks

 

That sounds like warped rotors. Pad/bushing issues would not react like that.

 

Sounds like rotors with excessive run out. Do you feel it through the steering wheel or brake pedal?

 

Could be the pads and residue transfer and build up. What kind of pads are you using? Pagid orange are known to cause this problem.

 

thanks for responses.

i feel it through the steering wheel only.

Rotors are cross drilled type.

Pads are BBK standard issue, not sure what kind they are.

another cause could be worn hub bearings?

 

They are unitized bearings not serviceable 4x4 bearings. Even at their point of failure there would be little to no play to cause wobble, where as their serviceable counterparts at the point of failure will seem like the wheel is about to fall off. Unitized bearing failures, there would be a lot of weird noises, a lot of heat coming from the bearing, and symptoms that very upon load and steering input, but not from breaking. The fact that you feel the standard steering wheel vibration under breaking means your front rotors have run out.

If you were to take off one of your front wheels and put a dial indicator on the rotor, spin it, you would see you have a descent amount of run out. Drilled iron rotors are machineable if you are within the wear limits, or you could just replace them. You would be surprised as how little it takes to make a noticeable vibration through the wheel. This is just because of how big the brakes are. A 10in rotor with .25mm of run out won't feel anywhere as bad as a 12.5in Porsche rotor with the same .25mm.

One thing that I feel causes this more then anything on cars with larger brakes is improper break in.

 

Hi Magnus,
Had the same thing.
Warped Rotors. I think I over cooked them once braking hard from high speed. I hadn't been over using them, a Deer jumped out in front of me and I had to do an emergency stop. I think the sudden heating up and rapid cool down did the damage.
Frank

 

19k thanks for the suggestions, will look into this.

thing is i hammered the stock system way harder than this one and they were fine. BBK should all things equal, be able to take more abuse.
The second hand set i got were pretty new. May be they weren't broken in properly and damaged to begine with. Had followed the break in directions for the rears and fronts by default at same time but perhaps laying into them exacerbated the already done damage. bummer.

"deer" reminds me of a mountain twist road that has stray wild cows, families of them, sometimes they rest on the road. you've seen the exploded chicken in porsche Im sure.

 

Exploded Chicken.... no whats that all about?

As to Discs I find that when using them hard repeatedly they are fine. I always seem to Bug**r discs with a one off braking action say emergency stop etc. Perhaps I should carry an anchor instead.lol.
Mountain roads are great. Some great ones here up North near Cape Wrath ( says it all ). Fantastic.

 

just an update. resurfaced the rotors and problem solved.