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Calculating tire size

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Post Tue Feb 02, 2010 4:45 pm

Posts: 56307
Location: DiabloSport World Headquarters

or, use this handy tire revs per mile calculator:
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Mike Litsch
Powerteq Customer Service Manager
Diablo Tech support by phone:
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Post Sun Feb 14, 2010 11:15 am

Posts: 63
I run staggered tire sizes; I assume I should use the tire size info from my rear tires for this I correct? :punisher:


Post Sun Feb 14, 2010 2:41 pm

Posts: 1007
Yes, the rear tires are the ones you use.
Certified Advanced EFI Calibrators for Ford, GM and DCX/Jeep Vehicles.

Post Sun Mar 13, 2011 8:23 pm

Posts: 11
There are all kinds of apps for smart phones too..

Post Sun Apr 17, 2011 10:30 am

Posts: 1
thank you!!!

Post Wed Jan 11, 2012 3:30 pm

Posts: 4
These calculations will get you in the ballpark. However, it has been my experience that your speedometer will be off by about 5 mph @ 80mph. I used my GPS to help me fine tune the value for the revs per mile in the tune. I ended up having to use a value of 880 revs per mile for a set of 275/40 R18 wheels. If you run this through your calculations it will tell you that you should be running 756 for the revs per mile.

Post Wed Oct 08, 2014 7:42 am

Posts: 4
I'm trying to do the tire Change on my truck and was wondering do I put in the revs per mile in the tire circumference? I'm running a 35x12.50x20.

Post Wed Mar 11, 2015 9:03 pm

Posts: 8
sup bruh ,im tried to recalibrate my speedo but it asked for diameter and mine says is 100.25 for a set of 275/55/20 lowest value is 500 what im doing wrong :normal:

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