Replacement Tire Question (Diameter)

[ramdulari]

It's not yet time to replace the OE tire that came in my V (Michelin Pilot HX MXM4). However I was looking at likely candidates on tirerack.com and the General Altimax HP's look attractive (survey rating, warranty rating and price). When I compared them with the Michelin's, I saw that the Generals are 0.1" less in diameter (although both are the same size spec). 24.6" vs 24.7".

So my question is, would replacing with the Generals cause subsequent trip computations (odometer, speed, mpg) to be wrong? I would guess the resulting error would be positive - the meters would clock higher than actual (or higher than factory calibrations).

Actually I did a quick calculation, and my conclusion is that the diameter discrepancy would result in ~ 405 miles error for 100,000 reported by the odometer as travelled on the slightly smaller diameter tire. I guess this is within acceptable tolerance (?)

[RodJo]

Originally Posted by ramdulari

It's not yet time to replace the OE tire that came in my V (Michelin Pilot HX MXM4). However I was looking at likely candidates on tirerack.com and the General Altimax HP's look attractive (survey rating, warranty rating and price). When I compared them with the Michelin's, I saw that the Generals are 0.1" less in diameter (although both are the same size spec). 24.6" vs 24.7".

So my question is, would replacing with the Generals cause subsequent trip computations (odometer, speed, mpg) to be wrong? I would guess the resulting error would be positive - the meters would clock higher than actual (or higher than factory calibrations).

Actually I did a quick calculation, and my conclusion is that the diameter discrepancy would result in ~ 405 miles error for 100,000 reported by the odometer as travelled on the slightly smaller diameter tire. I guess this is within acceptable tolerance (?)

There is a round off error there. If you go to the Michelin site, you will see that the Pilot MXM4's diameter is really 24.65". Anyway, that's close enough.