I went ahead and made an Excel calculator for the relationship between RPM and speed (in MPH). It takes into account tire size and gear ratios. Initially I made it for my own IX MR but I thought you guys might find it helpful as well so I have since added more tabs.

The spreadsheet is preloaded with tabs for the 2003 VIII, 2006 IX, 2006 IX MR, and 2008 X. These numbers are accurate in terms of factory tire size and gearing. I have also added a tab for the Lexus IS-F (also accurate) because it has an 8-speed and you can easily modify this tab for pretty much anything on the market right now.

I have tried to make the spreadsheet so that someone with practically no knowledge of Excel will be able to use it. As indicated in the screenshot below, only cells highlighted in green should be modified if you don't want to mess up any of the formulas.

The only other thing I would caution is to make sure to enter sidewall ratio as a decimal (.XX) and not as a number. So a 235/45R17 tire should be entered as .45 instead of 45.

http://www.filedropper.com/rpm-speedcalculator

If the above link should stop working for whatever reason, PM me your e-mail and I will be more than happy to send you the spreadsheet.

 

I think you should be able to upload it to this site, but I could be wrong. I'd like a copy of that though, appreciate the effort you put into making this. I'll PM you my email

 

Updated first post to include download link.

 

well that is a handy little thingy. thanks!

 

Good idea, and I have already done the same... One other word of caution, if you look through manufacturer sites and/or do your own measuring, you will find not every 235/45 is the same diameter, same with about any tire/size. Just be AWARE of that to end users who are needing dead accurate numbers.

Thanks for the work and sharing this with the evoM community. I have not been so outgoing with my efforts.