Here are the weights of the 3 kits you guys are probably comparing weights to the most. These weights are listed in the sticky: Weight Savings vs. Cost, on this forum section.
BRAKES
Stock assembly (F/R): 37.2/30.7 lbs
F caliper assemb: 14.5 lbs with pads and rubber line (Badfish weighed this)
F rotor assemb: 22.7 lbs (Badfish weighed this)
R caliper assemb: 11.0 lbs with pads and rubber line (Badfish weighed this)
R rotor assemb: 19.7 lbs (Badfish weighed this)
Brembo 365x34 (F) 345x28 (R) Kit
Brembo F caliper assemb: 14.0 lb (weighed by sparkyg)
Brembo F rotor assemb: 24.5 lb (weighed by sparkyg)
Brembo R caliper assemb: 9.5 lb (weighed by sparkyg)
Brembo R rotor assemb: 15.0 lb (weighed by sparkyg)
Cost: ~$6100
Weight savings: 9.8 lbs
cost/benefit: $622/lbs
http://www.m3post.com/forums/showthr...15#post5194815
Stoptech 380x35 (F) 355x32 (R) Kit
Stoptech F caliper assemb: 13.11 lbs with pads & bracket (Badfish weighed this)
Stoptech F rotor assemb: 21.01 lbs (Badfish weighed this)
Stoptech R caliper assemb: 11.15 lbs with pads & bracket (Badfish weighed this)
Stoptech R rotor assemb: 19.33 lbs (Badfish weighed this)
Cost: $5890
Weight savings: 4.6 lbs
cost/benefit: $1280/lbs
http://www.**********s.com/product.a...BK_E92_M3_RS10
http://www.m3post.com/forums/showthread.php?t=150944
Performance Friction 371x32 (F) 372x30 (R) Kit (prototype, production will use slightly ligther brackets)
Performance Friction F caliper and rotor assemb: 28 lbs with pads & bracket (James C weighed this)
Performance Friction R caliper and rotor assemb: 34 lbs (James C weighed this)
Cost: $8000
Weight savings: 12 lbs
cost/benefit: $666/lbs
http://www.m3post.com/forums/showthr...=232463&page=3
http://www.nexternal.com/bimmerworl/Product1060
Hope this helps some.