Quote:
Originally Posted by GyroF-16
Ok- here's my update:
I never found time to bleed the brakes.
I concluded that the issue was the "engagement point" in pedal travel- that is, I had to push further (than with my track pads) to get brake engagement, and even further to get full braking. Enough that I felt like the pedal was at the bottom of travel. This changed the pedal-height relationship between the brake pedal and the throttle, making heel & toe downshifts more difficult, as the brake was "below" the throttle under moderate to heavy braking.
Today I put my track pads (PFC-08) back on in preparation for a BMWCCA driver's school I'm doing on Saturday.
When doing the swap, I noticed that the street pads (PFC Z-compound) are noticeably thinner (by about 4-5mm) than the PFC-08s that I'm putting back on. I don't think this is due to wear- I've only got about 3,000 highway miles on the Z-compounds. I think the Zs started out thinner.
Also, my rotors are worn near the limits and will be replaced shortly after this track day.
With the track pads on, the soft pedal and lower engagement point are gone. (At least during my short test drive and the brake bedding series of stops). So the brake system and fluid are fine.
Question:
Could the thinner street pads, combined with the worn rotors, cause this noticeably-increased pedal travel and lower engagement point with the Z-compound street pads?
If so, is this anything I can change?
Would bleeding the brakes when swapping back to the street pads change the engagement point? Or will the calipers always retract to the same point, meaning that thinner pads will require more pedal movement before they come into contact with the rotors?
Gyro
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I missed earlier that you had installed the PFC Z rated pads. Sorry for that! Any difference in pad thickness would only be felt on the very first pump of the brake pedal after they were installed. After that it should make no difference. On the Z rated pads PFC installs an anti squeal buffer plate that's crimped on the the pad backing plate (see photo). What I found when I had them on my car is that anti-squeal plate acts like a thin spring and pushed to pad back a bit farther than you'd get without it. This causes a bit more pedal travel to close the gap and get the pads into compression against the rotor and the result is added brake pedal travel. I liked the performance of the PFCZ pads but hated the added brake pedal travel. When I swapped them out for a set of Hawk pads the pedal travel immediately went back to normal. If I ever decide to put them back on, I'm going to peel that anti-squeal plate off them and live with any noise that may come instead of the added pedal travel.