I'm trying to manually set my tire size using the Xcal2. The input formula is Revs Per Mile. I have Michelin LTX A/S, 255/65/17 tires. According to Michelin's website, that particular tire shows 692 revs/mile @ 45 MPH. However, when I go to the many tire calculators on the internet, most of them come up with 671 revs/mile. So which is correct?? BTW, I did find 2 tire calculators on the web that showed 692, but the majority showed 671. Which would be more accurate??

 

Hi.

Neither - mark off a spot on a rear tire & road, and roll it one rev yourself at the psi you are using. Measure the distance travelled. Do the rev-per-mile calculation from that linear true circumference measurement.

Some lucky folks with GPS's get it pretty spot-on too

Cheers
Grog

 

Cool, thanks... Just one more question: It is important that the procedure is done using the REAR tire versus the front tire? In daily driving, doesn't the front tire have a slightly lower rev-per-mile than the rear, due to the front tires being under heavier load?

 

Manufacturers revolutions per mile are determined with a "loaded" formula.
Kind of like 'load balancing" tires if you know what that is.

 

Hi.

I'm going on the premise that it's the drivetrain/rear wheels that are providing the speed data via the VSS sensor.

Heck - do both front & rear and take the average .

Cheers

 

Try to go to www.tirerack.com, usually you can find the manufactor Tire Rev Per mile spec on your tires.