Originally Posted by leigh
What speed do you think the 3.45 will top out at?
Assuming stock rear tire diameter (265/40-18, ignoring tire deformation), DCT, and 8400 and 8600 (increased with DME tune/reflash) rpm redlines:
Stock 3.15 FD with 8400 rpm redline: 209 mph 7th gear, 173 mph 6th gear
Stock 3.15 FD with 8600 rpm redline: 214 mph 7th gear, 177 mph 6th gear
3.45 FD with 8400 rpm redline: 190 mph 7th gear, 159 mph 6th gear
3.45 FD with 8600 rpm redline: 195 mph 7th gear, 163 mph 6th gear
3.62 FD with 8400 rpm redline: 182 mph 7th gear, 151 mph 6th gear
3.62 FD with 8600 rpm redline: 186 mph 7th gear, 155 mph 6th gear
These are theoretical top speeds based on gearing only - the M3's top speed will be drag limited (or speed limited if running a stock tune). I calculated the speed vs gear values quickly so I may have made a mistake...
I went with the 3.62 because 2nd gear will redline at ~60 mph with an 8600 rpm.