# Thread: Need help working out final drive ratios

1. ## Need help working out final drive ratios

Ok where do i start, basically i want to lower my gearing to something reasonable but i want to get an idea of what sort of speeds it would do in each gear with a different ring and pinion.

The car currently has a 3:39:1 fd ratio and will do ....

1st - 47mph
2nd - 74mph
3rd - 106mph
4th - 131mph
5th - 174mph

The ratios available to me are 3:66:1, 3:94:1 and 4.24:1, i'm guessing the higher the number the lower the gearing but by how much?

TIA

2. Theres a formula around somewhere to work this out.
You will need the gearbox ratio and (I think) the rolling radius of your driven wheels.
Will have a hunt around for you

This might work - not the one I was looking for though
http://www.xse.com/leres/ss/calculator.html

3. Nice one Eazi that was spot on, although i had the speeds a little out before, i didn't realise i can do almost 140 in 4th

So the choices are 160mph, 150mph and 140mph, i'll probably go for 150mph unless i decide i don't need to use motorways again

3.39 fd ratio Standard

Gear Ratio Final M@R R@80MPH
1 11.19 43.7 12803
2 6.58 74.4 7527
3 4.41 111.0 5044
4 3.53 138.8 4035
5 2.81 173.9 3220

3.66 fd ratio

Gear Ratio Final M@R R@80MPH

1 12.08 40.5 13823
2 7.10 68.9 8126
3 4.76 102.8 5446
4 3.81 128.5 4356
5 3.04 161.1 3477

3.94 fd ratio

Gear Ratio Final M@R R@80MPH

1 13.00 37.6 14881
2 7.64 64.0 8748
3 5.12 95.5 5862
4 4.10 119.4 4690
5 3.27 149.6 3743

4.24 fd ratio

Gear Ratio Final M@R R@80MPH

1 13.99 35.0 16014
2 8.23 59.5 9414
3 5.51 88.8 6308
4 4.41 111.0 5047
5 3.52 139.0 4028

4. Youve got a really long 5th gear havent you! My 4th to 5th change only drops about 500rpm.

Butuz

5. All of the gears are stupidly big tbh although i would love to keep 1st the way it is and drop everything else down. It can be a royal pain in the arse sometimes,e.g having to drop down to 2nd for a 60mph corner just to keep it in the power band.