is there a good way to figure what c rating lipo i need for my set up before i buy more batts. i already have some 5200 mah lipo`s with a 50c rating but haven`t used them yet and am going to buy 3 more for my other car but wan`t to make sure i don`t buy more then i need or more importantly to little.

Your motor will have a burst amp rating

Your batteries continuous rating needs to be higher than it

Example
100 amp burst motor

5000mah 20c pack = 100 amps available and borderline
5000mah 30c pack = 150 amps available and a much better option

Cheers

ok thanks i will check the motor ratings. i just looked at the novak spec chart and it dosen`t tell me the amp draw of the motor. its the 13.5 ballistic . do i need to do some math to figure the amp draw using the kv and watts ratings given in the specs.

Amp rating will be watts (power) divided by voltage

Cheers

ok so 26.35 amps is what the math shows for the novak 13.5 brushless spec. at 7.4v. so i guess my 50c batts should be fine then? also the gearing is a 4.8 ratio.

Yes mate that should be plenty

Higher rated packs should hold a higher voltage under load but its usually a case of diminishing returns

Spend lots of bucks for a small if any noticeable difference

Cheers