i am pretty new to the paved oval scene and i am trying to learn gear ratio's right now i am running in a stock 27 turn class and my gears are 100:28 due to tire size but normal gear set up once the tires are cut would be 100:32. i am looking to get away from the 100 spur gear and maybe do some experimenting is there any suggestions on gearing and we do run on a pretty short track. i know you cant suggest exact gearing with out the exact size of the track but i was hoping that some one could get me on the right track at least. please let me know all info would be greatly appreciated.

dave that is the right gear for MTR!!!!!!!!!!

We normally use a rollout when quoting what pinion size is needed, you need to know tire size and spur gear size. Most use the CO27 and sometimes the Epic X. Best solution to determine what has been your best rollout is first determine the diameter of tires by measuring them with a set of calipers (most racers' with have a set you could borrow. The formula goes like this to determine your rollout Tire size multiplied by PI (3.14) divided by Spur size multiplied by pinion = rollout. 2.25 (tire size) x PI (3.14) div by 100 (spur) x 32 = 2.26 Now to determine the gearing (pinion size) when you know the ideal rollout reverse the formula either when changing spur or tire diameter changes. Rollout x spur divided by tire diameter divided by Pi(3.14) = pinion. So if you changed to a 112 spur 2.26 x 112 divided by 2.25 (tire diameter) divided by 3.14 (PI) = 35.82 which would be more like a 36 tooth pinion.
Racers generally use a spur size that makes car feel better as far as speed and handling. I've tried ranges of 108, 112, 116, 120, 124 and in stock a 116 feels better for me, others I've talked with use others sizes. When I tried them the car didn't feel right to me.

i appreciate the help. and i have been trying to figure out the formula to do roll out. but i really agree with what you said at the end of your post. not every car or every driver is the same you have to gear your car to make it drive the way you like it. so maybe you can answer this question? i actually ran a 100:29 gear set up today. if i wanted to do some changing and say i put on a 104 tooth spur gear would i use a smaller(ie.23) or a bigger(ie.37) pinion gear to keep it pretty close to where i am now any help would be awsome. one last question i am moving up a class this in the next week or so to a 19turn class and i know those dont get geared the same what size gears would be standard in that class. thanks in advanced
david doughboy ridings

To keep same ratio, if you go to a bigger spur, go bigger pinion. Smaller spur, smaller pinion. 100/29=3.44. 104/30=3.46.

thanks!!!!!!! that's exactly what i was looking for