Brake vibration issue

[TRES]

My front brakes for some reason vibrates under repeated hard braking (ITS NOT THE ABS). e.g. During high speeds I hit the brakes the car stops fast and smooth. after 2 high speed runs when i hit the brakes it vibrates and shake. I thought the rotors were bad or had deposits but the dealer said its fine and they switched out my rear brakes. Any ideas what might be causing this.

[LostMarine]

no idea brother

[TRES]

checked my shocks and they are all fine will check the bushings thursday and maybe replace the brakes and see if that helps

[Sticky]

No idea either. Wish we had a brake expert.

Let us know what you find when you check the bushings.

[DavidV]

they switched out my rear brakes

This I don't get. I thought you said you have problems with your front brakes.

Most likely reason for the shaking is a bad rotor. One of them (or both) apparently warps under heat, most likely because you have once held the brakepads on the disks too long after heavy use. It could very well be that the disks are straight when cool, so on normal day to day use you don't notice anything.

[Autobahn335i]

Which brake pads do you use?

I've had this happen with Cool Carbon pads and EBC slotted rotors after a trackday on a track with a hard braking zone. Either the pad deposit was uneven, the pads got glazed or the rotors got warped due to heat. Cold braking was fine, but once the brakes were heated up they vibrated like crazy.

In any case I decided to get a proper BBK as most other brake "upgrades" are just unsufficient for track duty with our heavy cars.

[TRES]

Im on stock pads I will order some new rotors and pads and see if it helps because my bushings are good. Need to save for bbk it costs 6k

[DavidV]

Im on stock pads I will order some new rotors and pads and see if it helps because my bushings are good. Need to save for bbk it costs 6k

A mild upgrade could be switching to BMW Performance rotors.
Stays cooler under not too heavy track use.
By no means a big brake conversion difference, but noticable.
And only a few $10,- notes per disk extra

[TRES]

Yes i told them the front brakes and they said it was good


thanks man this makes alot of sense now so it looks like the rotor might be the culprit the vibration sounds like rolling over rumble strips. I could go the dealer and replace the brakes under warranty but I guess the same issue might resurface.

This I don't get. I thought you said you have problems with your front brakes.

Most likely reason for the shaking is a bad rotor. One of them (or both) apparently warps under heat, most likely because you have once held the brakepads on the disks too long after heavy use. It could very well be that the disks are straight when cool, so on normal day to day use you don't notice anything.

[Snertz]

have you tried rebedding the pads? does it occur at all speeds or just high speeds?

[TRES]

so i did some testing today I made a few 30-85mph runs after the 4th run it started to shake. I let the brakes cool for a few repeat runs after the 4th run same result. So i'm guessing the rotors are warped which only has 30k miles on them.

have you tried rebedding the pads? does it occur at all speeds or just high speeds?

[Sticky]

so i did some testing today I made a few 30-85mph runs after the 4th run it started to shake. I let the brakes cool for a few repeat runs after the 4th run same result. So i'm guessing the rotors are warped which only has 30k miles on them.

That makes sense, likely the rotors.

[bluejae]

if not the rotors being warped... it could be the wheel bearings... but i'm no expert... just that something similar happened to my dad's car... and rotors were fine... replaced the wheel bearings... problem solved...

[TRES]

The wheel bearings are fine its the rotors. wheel bearings will be noisy as speed increases also you can jack the car up and spin the wheels and you can hear a humming sound.

if not the rotors being warped... it could be the wheel bearings... but i'm no expert... just that something similar happened to my dad's car... and rotors were fine... replaced the wheel bearings... problem solved...

[Curtis17]

I think you should follow these instructions. You will defiantly find the problem and also solve the problem. Did you check the rotors for run-out and variation in thickness? The rotors could be warped. It takes only a few thousandths of either thickness variation or run-out to get brake pulsing. But, if your rotors are in good shape, suspect the fit of the pins with the calipers. If the pins and calipers have a sloppy fit, the caliper can cant out of true and create pulsation in the braking force. If the calipers are stuck on the pins, the calipers can not slide to adjust for wear differences between the inner and outer sets of pads and the rotors will be pushed out of shape causing problems. Typically, pads on the piston will wear faster than the ones on the caliper when the caliper is stuck on its pins. The piston pads tend to wear a bit more than the caliper pads becasue of friction between the caliper and pins.

Hope this information will be useful for you. please inform me if you found this information helpful.

with best regards.

[Sticky]

^ Nice post, thank you.