According to hpi here the diff ratio is 2.16.
http://archive.hpiracing.com/kits/rtrsuper/rtrsn-ss.htm
So you could check brians site and calculate what the speeds are. You should be able to gear higher if needed. I've learned alot from the isc forum and the uk forum. esc setting also help with going fast. Good batteries are a big help. What are your esc settings? I run a TC4 with a neu 1509 1D (6700kv) Its geared 49/60 right now.