Rx7Rob

I recently changed from PFC99 rear pads to Raybestos ST43's and am cracking rear rotors too fast. This is with stock calipers and OEM rotors.

The rotors used to last a crazy long time with the PFCs but would wear with circumferential grooves and minor spider web cracking. With the 43's the rotors look great. None of the light cracking and the surface was wearing but staying flat (always looked like they were just machined). But they crack with low hours. Crack is straight out to the edge and on both the inner and outer surfaces.

I haven't changed anything other than the pads.

Any ideas? Is this typical with the 43's? Any suggestions for a different compound to use?

Thanks

Rob

96CollectorSport

Quick thought here - but the ST43 may hold more heat - or hold heat in longer than the PFC pads did - after the car is sitting in the paddock for 5 minutes move the car so the wheel moves 180 degrees and see if that helps. Since the rotors look good otherwise and then get a large crack the issue hear seems like thermal shock. Worth a try at least

ckchan10

SouthernSon

Do you run with A/H engaged? If so, this is your main problem. It eats up rears. But, if you intend to do many more track days go ahead and get some really good 2pc. floating rotors. Seriously, you will be way ahead in the near future. It took me at least 4 dozen rotors over the years to get this through my thick head. Also, if you envision needing better braking overall in the near future, get some more 18" wheels for square for all four corners to enable use of 14" rotors up front and fixed calipers. I know, a lot of money in the near term but a lot of satisfaction immediately and savings in the future. The only upgrade you will want later is matching calipers on the rear. Brake problems solved, not to mention some aftermarket calipers use very inexpensive pads such as wilwood. Save on rotors and pads while stopping car with ease. However, if you don't go to the track very often, I would suggest just stay with OEM.

Rx7Rob

Good suggestion about rolling the car! I forgot about that. I tried it years ago to see if would help with the normal light cracks. It didn't do anything so I had stopped. I'll try it again next season.

SouthernSon, I have a WW BBK (front only race kit) in boxes ready to go on this winter! Have another set of 18's for the front, just need to decide if I'll go 275/305 or 315 on all four (and figure out how to get the rake). Car is a 2000 so no AH.

Guess for now I'll stay with OEM rear rotors (or try the centric premium everyone talks about). If they keep cracking too quickly, then I'll look to upgrade the rear.

Thanks

Rob

0Todd TCE

Too little rear rotor. With ST43 you're pushing rear bias in the car and doing so with the same size heat sink. The rotor can only manage (absorb and dissipate) so much of a heat cycle.

Larger rear rotor with less aggressive pads. Same functional value but with greater mass for longevity.

Rx7Rob

Now that may be it! I had been running PF01's up front. They felt much more aggressive than the 43's. So I went from:
PFC01 front / PFC99 rear - rear rotors lasted forever
PFC01 front / ST43 rear - rear rotor life not as long as before
ST43 / ST43 - significantly shorter rear rotor life (but brake balance still felt good)

I'm also using the DRM brake bias spring which gives a little more rear bias. Several months ago I sent DRM an email inquiring as to how much it shifts the bias, but that went unanswered.

Unfortunately none of that helps since I'm changing the fronts to a WW compound with the BBK. Rear compound will just be a guess regardless of the manufacturer. Not even sure how the front pads that came with the BBK will feel. I want them to be at least as good as the stock calipers with PFC01's (which were truly awesome).

hanseng1

0Todd TCE

As a side bar to you rotor question/comments I'd urge you to change rotors with the new pads. Not just the pad themselves. You're playing with fire with the manufacture changes and the swapping of compounds. I can say from customer experience that putting other pads over the PFC pads will surprise you; like you won't stop. Never change suppliers (and to an extent compounds) without consulting the manufacture on compatibility from one to the other.

ponycar

I second the recommendation to use the DBA rotors from KNS brakes. Inexpensive and much better metallurgy than the GM rotors from the dealer and others I have tried with aggressive pads.Ken at KNS will treat you well.

Rx7Rob

Anyone using the SpecCorvette rear rotors (PowerStop AR8261XPR)? They look to be about the same cost as the OEM rotors (115 / pr). Don't like that they're drilled.