pignon e-maxx
 

I have Tekin RX8 + motor 2250kv

what pinion should I use in 'e-maxx

4 cells A123 = pignon ???

6 cells A123 = pignon ???

with this kv motor it will be good to use 24/58 on 4s and 22/62 on 6s.
Have fun

I have spur gear = 68T

I thought a ratio = 18.67 for 6A123 is ok?

4 A123 cells = not enough voltage/power.

With 6s A123 cells, I would gear around 68/18 for ~40mph (new 3905 emaxx, stock sized wheels).

Thats plenty of speed, but remeber that 6s2p ( 2x 6s in parallel) is much better and safer for the batts and esc compared to just 6s.