Poll: Brake upgrades..what kind of ratio?, F=big/R= big or F=big/R=little or ??? Options

[Mueller]

okay...for a factory 914 /4, the front calipers (piston area wise) are 1.61 larger than the rear....(42mm and 33mm)

for early 911's (up to '84), the fronts are 1.6 larger
from '84 to '89, the fronts are only 1.3 times larger than the rears....then the ratios vary from 1.4 to 1.7 until the arrival of the 1st Twin-turbo, that car has calipers that have piston areas 2X the size of the rears !!!!!

I'm just wondering what combo people have successfully ran.....it's interesting to note that the standard Boxster front calipers if bolted to the front of a 911, the Boxster piston area is only 1.05 larger than the standard 911 fronts.....seems like a darn near equal swap, except for the bigger pads you get with the Boxster calipers (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[lapuwali]

QUOTE (fiid @ Feb 16 2005, 11:06 AM)

QUOTE (bondo @ Feb 16 2005, 10:44 AM) QUOTE (fiid @ Feb 16 2005, 11:13 AM) (IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) I think you hit the nail on the head.   Pad area would effect wear rate, and I bet it has some thermal effects too - like felxing you mentioned. If you assume that the braking force originates (on average) from the center of the pad, then a bigger pad and larger radius rotor whould also move the braking force further out, giving it a greater mechanical advantage (of course - larger tire radius would lose you this battle from the other end).... Now that I think about it, pad area and heat MUST be very related. If friction is the same for a smaller pad (or nearly the same), the amount of heat energy must also be the same, because dynamic friction is simply the conversion of mechanical energy to heat. So that same amount of heat would be concentrated on a smaller pad area and overheating it sooner. I guess the same thing would apply to clutches. Too bad our bellhousings are so darn small. (IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) what you said.

Thanks. I've been saying this for YEARS, and no one listens, since pad area is "obviously" related to braking power.

Yes, pad area primarily affects pad wear. It can also bring on fade if the pads are small enough that they get so hot their coefficient of friction falls. By itself, pad area has NO effect on clamping force or braking effectiveness.

I'd also hesitate in quoting 911 brake balance figures when talking about 914s. Static weight distribution definitely matters. I'd use Boxster figures, though, with a small grain of salt. Remember that the height of the CG also comes into play, since it affects weight transfer rear to front under braking. A lowered car needs less frontward brake bias than a car with stock ride height, as less weight will transfer forward under braking, so the rear brakes can contribute more to stopping.