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      12-09-2009, 10:48 AM   #11
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Drives: E30 M3; Expedition
Join Date: Apr 2007
Location: USA

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Originally Posted by jml View Post
For fading reasons, or behavior? I'm more after understanding if the bias is important (vs the other issue that come along with different pad types).
In dry track conditions with 265/285 BFG R1s, I "perceived" a slight drop in performance as in ABS was more willing to kick in. I assume that is because the bias was shifted more forward. The rear pads lasted much longer than the fronts, which they shouldn't, and that's indicative of them not doing as much work as they should. That was confirmed when I observed highly uneven temperatures across the front and rear rotors. When the rear RS19 finally became available, I put them on, and ABS seemed to kick a bit later under threshold braking, and temperatures were much more even between front and rear rotors. That meant that the front pads were less likely to fade; I must assume BMW sized the OEM rotors for conditions that resemble track driving (because in daily driving you won't get near the thermal limits of the rotors). Also, front and rear pads wore out at a somewhat similar rate. It is probably best to leave the stock bias alone or shift it back slightly in a mostly stock car. If one makes modifications that result in significant changes in F/R traction and/or ride height, then bias might need to be adjusted as well.