[mjderstine]

thanks, i always wondered why you guys put 4s when cells clearly starts with a 'c' whoops.

i would say my track is pretty tight. the straight cant be more than 80-100 feet max, its a quick blip of the throttle and its over. so perhaps 30mph would be fine. and as you say, upgrades in the future always tend to happen...
these are the numbers i got on 16 pinion. probably not a bad place to start.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 16
Total Voltage: 14.8
Motor KV: 1600
Tire Diameter (inches): 4.1
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.007
Spur/Pinion Ratio: 2.88 : 1
Total Ratio: 9.50962 : 1
Tire Circumference (inches): 12.88 inches (327.17 mm)
Total Motor Speed: 23680 RPM
Vehicle Speed: 30.37 mph (48.79 km/h)
Effective KV Value: 1600
KT constant: 0.85 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...