[gippy]

so here are the sequence of events...

put in some decent track pads (pagid RSL 29's)
bedded them in (about 8 hard stops from 60mph rolling in between each stop)
went to track - did 4x 12 minute sessions.

I just cannot remember now if the vibration started quite early on or whether it appeared at the end, but by the end i was getting vibration through the pedal accompanied with a droning noise which reduced pitch as speed reduced, braking from 140mph.

anyway, track day ends, back on the drive home at normal speeds - experiencing the same vibration as the speed dropped through 40mph to about 20mph.

swapped the track pads back to the OEM ones - same result.

Its less pronounced if i apply greater brake force- but if i'm gently riding the brakes coming to a traffic stop for example, thats when its at its worst.
And because its only happening from 40mph down, basically i get to experience it all the time around town.

I'm not sure if i've warped the discs or if theres just track pad material on the discs which need removing.... what do you guys think?

what are my options?

- buy new OEM discs and a set of performance discs purely for track days
- keep on driving and see if it goes away as the track pad material clears away?
- get the discs skimmed? and if it still does it, its definitely warped discs?

(car has M performance brakes, S2NH, 370mm rotor front)

[BMWILUVU]

Alot of material on the rotors and those are hard pads. I vote for bad bedding. Did you run with DSC off?

[gippy]

Originally Posted by BMWILUVU

Alot of material on the rotors and those are hard pads. I vote for bad bedding. Did you run with DSC off?

At the track I did yeh.

[Billfitz]

In the bottom picture there appears to be some discoloration of the rotor, a bluish tinge. That comes from overheating, overheating causes warping.

[FaRKle!]

Originally Posted by Billfitz

In the bottom picture there appears to be some discoloration of the rotor, a bluish tinge. That comes from overheating, overheating causes warping.

Bluish tinge also comes from pad transfer layer. I seriously doubt he was overheating the rotors. His brake fluid would've gone before he warped the rotors. Also the rear rotors tend to get hotter than the fronts on the track IME (there's not as good cooling back there).

The bedding process seems a bit light to me. I've had RSL29s before and typically would do some long light braking to scrape off my street pad transfer layer and slowly build heat up into them before doing the hard stops. Your pics look more like uneven pad deposits to me.

I would just drive on them and see if it goes away with time. Whenever I swap my street pads in right after a track event there's always a small amount of pedal vibration that goes away when the track pad transfer layer wears off of the rotor. You can probably hasten the process by running your track pads on the street and keeping them cold (when they're most abrasive).

[Billfitz]

I'm referring to the spot in the upper right of what's visible of the rotor, not the overall color. It has the look of a hot spot. A picture without the wheel in the way would help.

[jh_f30]

Could it be caused by applying the parking brake after a run without giving them ample time to cool down?

[gippy]

Originally Posted by FaRKle!

Bluish tinge also comes from pad transfer layer. I seriously doubt he was overheating the rotors. His brake fluid would've gone before he warped the rotors. Also the rear rotors tend to get hotter than the fronts on the track IME (there's not as good cooling back there).

The bedding process seems a bit light to me. I've had RSL29s before and typically would do some long light braking to scrape off my street pad transfer layer and slowly build heat up into them before doing the hard stops. Your pics look more like uneven pad deposits to me.

I would just drive on them and see if it goes away with time. Whenever I swap my street pads in right after a track event there's always a small amount of pedal vibration that goes away when the track pad transfer layer wears off of the rotor. You can probably hasten the process by running your track pads on the street and keeping them cold (when they're most abrasive).

I just booked the car in to skim the rotors on Monday for £95... How long do you normally have to drive around and brake for track pad transfer layer to wear off?

[FaRKle!]

Originally Posted by gippy

I just booked the car in to skim the rotors on Monday for £95... How long do you normally have to drive around and brake for track pad transfer layer to wear off?

A week or two. It progressively gets less and less.

[gippy]

Originally Posted by FaRKle!

I would just drive on them and see if it goes away with time. Whenever I swap my street pads in right after a track event there's always a small amount of pedal vibration that goes away when the track pad transfer layer wears off of the rotor. You can probably hasten the process by running your track pads on the street and keeping them cold (when they're most abrasive).

done some further research on this and yes a number of other sources have said the same thing.

Either my discs are indeed warped...or....
i've left uneven deposits on them, and really what I should have done is left the track pads in for a few more days and used their more abrasive material
to clean the surface - then put my old pads back in.

Seems like i can do 1 of 4 things:

- get them skimmed £95
- buy a rotor hone tool for £50 and clean the discs myself
- swap the pads out again and use the track ones to remove the deposits
- drive around with the normal pads as you say

skimming requires the least effort......i assume skimming is effectively cleaning the discs ain't it? as its just skimming the 'old' surface away with a lathe.

the other thing i dont quite get is - if you need a harder material to clear out that track pad transfer layer - how would the normal pads do it, if its material isn't as abrasive?
or would the heat generated slowly remove it over time?

[BMWILUVU]

You will eventually figure out that using the same rotors for daily and track pads is not a super thing.

[cfm56d7b]

This is a case of hard / rigid pad meeting OEM rotor under more aggressive conditions than daily driving. Quite common.

[zinner]

take off the wheel and run your hand on the rotors (while cool of course) your fingers are a good tool outside of a real guage to measure run out. If it's pad material you can just do some hard brakes to remove it. Or at least that has worked for me in the past.