XRAY - Model racing cars

Hello,

i just want to know best gearing choice for t4 pro stock racing. I will join pro stock club race with a t4 and i would like to use 106T spur 50T pinion (64p) or 104t spur 49t pinion. does it important to reduce size of both for example 97t spur and 43t pinion? what is the effect of changing size even if the raito remains 4.00 ? i understand that if i use too big or too small spur-pinon set it wouldn't fit my car. thanks for replies.

regards

By pro stock do you mean 13.5T boosted class?

yes i mean 13.5t boosted class. we have a 4.0fdr limit.