Hi
a couple of links to some useful charts to get your head round... the first one tells you your final drive ratio which for a 2wd buggy is 8
the second one you need to find how many teeth the spur(biggest plastic one) has on your car
then get as close to 8 as you can.. then the pinion size you need is on the left
hope this helps a bit
http://teamnovak.com/tech_info/view_article/26
http://www.petitrc.com/setup/associa...fRoadRatio.pdf