[s-cars] "Warped Rotors"?? was Things I want to know...

[Keith Maddock]

That "warped" rotor feeling is often the effect of uneven pad material transfer onto the rotors.

Usually this is caused by failing to bed the brakes in properly - A proper bed-in procedure establishes a even transfer of pad material onto the rotor.  Without this, when you use the brakes hard, there will be uneven spots of pad transfer on the rotor, and it feels like warped rotors.

If you are running "track pads", then you need to re-bed them in before every track event if you have been doing street driving  in the meantime.

However if you are running street pads on the track and overheating them, they can also leave this uneven pad transfer on the rotor.

When race pads are cold, they tend to operate in "abrasive mode" which will tend to clean the pad-transfer off the rotors (hint - this can sometimes work to smooth out the uneven transfer).

I've had a lot of brake pad problems this year since I go to the track (Nürburgring) quite often with my daily driver.  Stock Textar pads were unable to handle the heat that I was generating and had a large problem with uneven pad transfer.

(root cause is that I need larger rotors to handle the heat but this is either difficult or expensive due to the inspection laws here, but I will have some soon).

Both Pagid Orange and Pagid Yellow pads proved to be the type that were very sensitive to being bedded-in properly - if not properly bedded-in (or rebedded in for each event), then they exhibited the uneven pad transfer quite horribly - and they were unable to "self clean" with cold braking.

Now I'm on my 5th set of brake pads since March - the 4th and 5th sets have been Hawk Blue's (9012) and they are *great*. We also run them on our MkII Golf "Ring-Tool".

The uneven pad transfer problem is gone, and they do not require "re-bedding" each time I go to the ring.  Pad life is also better than the Textars or Pagid's.  Also, they offer a significantly more consistent friction level with temperature changes compared to the Pagids.

The only downfall to the Hawk Blues is that the dust is slightly corrosive, but to date I have not noticed any problems with this.

If you made it this far, and have some more time, I have compiled a lot of info here:
http://keith.maddock.com/bremsen/
You can read my (painful) story of trial and error as I have learned a lot about brake pads and rotors this summer.
Unfortunately I have not yet taken the time to update with the info from Hawk Blues.

The following is also an excellent link
http://www.stoptech.com/whitepapers/warped_rotors_myth.htm


Cheers,
Keith


Keith Maddock, TRW Automotive,  Koblenz, Germany
Slip Control Systems, Systems Design, Traction Control
+49 (0)261/ 895 2474    -   -   keith.maddock at trw.com