FDR
 

Can any one tell me, if wanted a FDR of 7.93 what is the better way to get it. A spur of 61t and piñon of 20 or spur of 58 and pinion of 19. They both will do a FDR of 7.93 is one way better than the other.
Cheers

No difference in speed but there will be a slight shift of weight form the motor depending on what you choose.

True. Only difference will be motor position - and therefore weight distribution. But we are talking about small differences here - in this case here, assuming we're talking about 48dp, the motor would move ~1.1mm.

The maximum change I can reach in motor positions, while staying with the about the same gearing on my T4'17, is ~3.5mm (calculated for a target FDR of 5.0, or closest possible, without ever going any lower (so no 4.999s), the combinations with the max. distance in 64dp are 37/98 and 42/111, with actual FDR varying from 5.021 to 5.032, between those extremes, while the in-between 38/100 will hit a perfect 5.000 spot on).

Fdr is fdr, use the best combination for your particular car

You may get slightly better wear using the larger pinion.

Cheers,
Jim

Do not forget the gyroscopic effect of a larger spurgear....:lol: