I upgraded the front stock 4-piston 330mm brakes to Stoptech BBK 380mm, 6-piston brakes a couple of weeks ago and am experiencing what I can only surmise is front brake bias. The ABS starts to kick in as the car is coming to a full stop and I have noticed that the front end dives more now than with the stock brakes.

I have read other threads and am impressed with the depth of our members' knowledge of braking systems and how changing to larger brakes up front affect the car's braking balance. It seems that even upgrading to the 996 GT2/GT3 6-piston Porsche calipers and 350mm 997 rotors up front it is recommended that the rear brake rotors be changed from the 330mm stock 996 turbo calipers to the 997 350mm rotors with spacers (unless using the GT3 rear calipers) and more aggressive pads (l.e. Pagid blacks).

So, I'm thinking of changing my stock 330mm rears for the 997 turbo 350mm rotors and getting some adapter spacers from Vivid Racing and Pagid black pads. But, I'm concerned that my upgrade to 380mm rotors, rather than 350mm rotors, may require more rear braking force than the stock 996 turbo calipers produce, i.e. going with the 997 turbo rear calipers since they have a larger piston area and generate about 48% more rear braking force. What do the brake gurus on this site think? Should I stay with my stock rear calipers or get the 997 rear calipers? Your help will be greatly appreciated since I know I need to change the rear brake set up and I plan to do it soon. Thanks in advance.

 

i have 997 turbo rear calipers (front also) and my car brakes better than my friend who has 6 pistons fornt and stock rear with more aggresive pad. My car feel more planted. You will get a longer pedal travel and a little more mushy because the master now has to move more oil.

 

380/330 if a bit too much. Get a set of 350 rears with Pagid blacks or PFC01s to go with your 380 fronts and you will be good to go. The problem making things worse may be that the stoptech front binders may have a greater piston area than the GT3 6pots making things even worse. Dunno...

 

Thanks for the feedback guys. I'm going to first try to resolve this problem with the 997 350mm rear rotors, Pagid Blacks and the Vivid Racing spacers. If that doesn't work then I will try to solve the problem by adding the 997 rear calipers.