I use trinity Tmaxx springs in the rear
http://www3.towerhobbies.com/cgi-bin...&I=LXHWJ7&P=ML. That tranny is pretty heavy and bottoms out quickly. My setup is about 5 lbs including batteries, Heavier with the beadlocks, so the stiffer springs are a must in the rear. The front has some green associated springs.
6 KiloWatt A123 Racer
GTP-Pletty Big Maxximum+RX8. GTP-C50-6L Hacker+RX8. CRT.5-Pro4+ZTW esc.
24s2p EVG SX 49.6mph Ebike.
18s4p Raptor 60mph Ebike. 11.5KW