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      03-18-2013, 07:02 PM   #79
ortho281's Avatar

Drives: 2011 E92 M3 6MT
Join Date: Aug 2010
Location: Katy, TX

iTrader: (1)

Originally Posted by r53s65e90 View Post
I went through the same thought process about this before deciding on the 365 kit. 380 has definitely more heat capacity but what does this mean? My calculations were as follows: Based on geometry the 365 rotor is about 4.6% lighter. Given that all other stuff is the same (slotted, same caliper, same pads, same cooling effectiveness) and assuming all kinetic energy goes into heat to the front brake (which is the absolute worst case) here is what it means: If you fade (=boil fluid) the 365 kit during braking from 110mph to 40 mph, the 380 kit will fade from 112mph to 40 mph. To me this means NO perceptible difference, especially if you factor in cooling and the fact that part of the heat will go tot he back brakes. So I get to keep my 2 sets of stock 18s too.

I didn't bother with rear brakes calculations as I consider them a cosmetic mod.

I couldn't make the same calculations with the stoptech setup because caliper and pads change from the 380 to the 355 kit.

Would be nice if someone could replicate my findings.
Yes, the stopTech does use bigger calipers, rotors and pads for the 380 vs the 355, so heat disapation differences may be greater. At TWS, where I mostly track my speeds are around 140 mph on front straight and 110 on back straight, so brakes heat up quite a bit. I went with the 380's for this reason and they fit my Apex 18" Arc-8's.

Akra GT4 / MS Stage 2 / MS UDP / BPM Tune / KW CS / H&R Sways / TMS Delrin / ST 380/355 BBK / Cantrell 2.5" Ducts / SR34 Pads / Apex Arc-8 / Hoosier R7's / Mode GT4 Splitter / GT4 Canards / APR GT-250 Wing / Cantrell Half Cage / Recaro Pro Racer / Schroth Profi II-6 / BMW Alcantera Wheel / Cool Shirt / ESS Fire Supp / Solo DL