[WallyF]

espo89,

Thanks for the spread sheet. I am interested in how you arrived at the numbers. Where do you get the "336" factor? Can you write down the equation for the rolling diameter thtt you arrived at?

I have a similar spread sheet that I made up for the full range of tires and rims for the E90. I got the manufacturer's data from their web sites.

It calculates the unloaded tire diameter for reference. It then calculates the tire rolling diameterin inches by dividing one mile distance (5280x12=63360 inch) by pi(3.1416) and the manufacturer's revs per mile specification. From this I multiply by the rear end ratio and 6 gear ratio as you did to get the RPMs for 60 MPH. I used the average rolling diameter to establish the calibration for the speedometer that BMW uses.

I WAS UNSUCCESSFUL IN UPLOADING SPREADSHEET AS I DID NOT SEE THAT I NEEDED TO ZIP IT FIRST. I AM GETTING WINZIP AND WILL POST THE SPREADSHEET SOON!