final drive ratio
Turbo Mini Forums

sorry i know this has been asked so mny times befor but i'm using 10" wheels on my new build gonna be used for the occasional drag race and was wondering if a 3.44 fd was a good choice how much top end would i lose bearing in mind that the standard ratio is 3.2? would it be lot more revier (made that word up!) sorry just confused any help greatly appreciated.

I have done a simple calc to work out max top speed using this setup.
Rolling diameter of a 165/70/10 tyre is *roughly* 1523mm/rev.
Assuming 6000rpm rev limit, divide by diff ratio to give revs to wheels in top gear (direct drive ratio, 1:1 drops) = 1750rpm.

1750rpm * 1523 mm/rev = 2654826 mm/min

Converting units gives 160 km/h, converting again gives 100 mph. I have rounded all those answers and also I calc'd the tyre rolling circ so won't be spot on, but will give an idea. Working out for 3.2 diff ratio gives top speed at 6k rpm of 107mph.

ROUGH CALCS ONLY but you get the idea.

gav
toms done it for you!

i would stick with the 3.2 standard F/D on 10s