My gearing is too low in my car, and I want to figure out what diff I need to get me a better top end.

Anybody recommmend an online calculator?

If you send me your email, I will send you an excell one that I modified from an online one. You can alter tyre sizes, diff ratio's and gear ratio's to give the speed in any gear at ant RPM

here you are

No dis-respect Austen but I like my spreadsheet better. I did get the take 98% of the rolling radius from that one though.

Jasper, try this thread http://forum.locostbuilders.co.uk/xmb/viewthread.php?tid=4662 sixth post from the top. You can put in the exact ratios for your g/box and exact tyre/wheel sizes to get a theorectical top speed at x rpm.

HTH

Cheers chaps, I'll get to work on that one.

jasper....... you should have one with the digidash softwear???? i did, its wot i used.