Quote:
Originally Posted by sp_cs
Curious why?
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It's probably in the above stuff somewhere, but once again
The function if the brakes is 2 fold
1) apply braking torque to the wheel
2) process the heat generated in 1
There are several restrictions that need to be applied to any modification of stock brakes
1) f/r bias must be maintained, while more front is safer more rear is desirable from a performance perspective.
2) pedal ratio must be kept w/i a fairly narrow range, the exact spec will depend on boosted or no and how much leg the driver is willing to employ and for how long
3) the brakes must fit w/i the wheels used
4) the tires should be adjusted up in grip when brake torque is raised
5) calipers should not make the processing of heat more of an issue than it is stock. This is particularly relevant to track cars.
Boxster conversions to 911 brakes are not an upgrade because the violate rule 1 & 5
Rule 1 - stock f/r bias for all 911 through '83 is 1.491, this is a great place to be, for track work bias a little less than that can be employed but to do so the car wants a really effective lsd and wants to be lower and stiffer
F & R Boxster change has a bias 1.669. This isn't dangerous and is fine for street use but gives up a lot of performance in track use as the fronts are doing too much work which causes more thermal issues and the rears are loafing along doing little to help the cause. Boxster f w/ Carrera 3.2 rear is better w/ a bias of 1.554, still not as good as stock.
Rule 5 - the Boxster calipers do generate more brake torque but brake torque has rarely been an issue w/ 911 brakes. Heat is and always has been the primary concern. Boxster fronts generate 1839n-m of torque @ 70 bar line pressure. 911 brakes generate 1444n-m @ 70bar line pressure, this 27% increase in torque going through the same rotors causes at least 27% more thermal issues. The pads and rotors and fluid have to run at higher temperatures when they were already near max to begin w/.