Originally Posted by bornox
hi! i have a question about FDR for touring car. internal ratio is 2.0 and i have 96 spur and 48 pitch pinion final drive ratio is 4.0 and i have 98spur and 49pitch pinion final is 4.0. both has the same FDR whats the difference for both or is it the same? thanks!
There is such a small difference between those spurs that you'll most likely never notice any real
difference on the track. Big V. Small spur gears with same FDR
has been debated for years and it comes down to several things: slight handing changes because of changed CG of the car by moving the location of the motor (but usually it is noticed with really big differences in the size of the spur sort of a "Duncan" sized SPUR and a "Parker" Sized SPUR) and some efficiencies in better gear mesh with bigger gears. There are some valid arguments about changes in rotating mass that would affect acceleration, but in a touring car the pinion and spur are a relatively small proportion of the total rotating mass of the car so that the effect would be very very minimal at best. IMO most other claimed effects are just placebos. (Sorry I'm from San Antonio and couldn't resist the NBA pun). GO SPURS GO!!!
+1 for Thomsva re mixing pitch and the number of teeth, but bornox in his question is changing both the spur and the pinion (98 sized spur gear and a 49 pinion) to keep the same FDR so that the only different is the size of the gears being used.