Calculated tire size comes up short - a scam?

[PyrPatriot]

Using Falken Wildpeak 35/12.50/17 M/T01 as an example. I tried this with KM3 and other tires to the same conclusion

There are 63360 inches in a mile. The circumference of a circle/tire is Diameter multiplied by Pie (3.14159265...). Revolutions per mile is thus 63360/(PIE x Diameter). This becomes 609 = 63360/(3.14159265 x Diameter). Solving for the Diameter we get Diameter = 63360/(3.14159265 x 609), which yields 33.117 inches. Thus your 35” tire is actually 33”. Even accounting for a manufacture’s website’s listing that the overall diameter is something like 34.8 inches, you are leaving customers 1.7” short of tire diameter.

For example: Falken’s 255/75/17 calculate to be 31.2”, but they report 32.3”. Similarly Falkens 35/12.5/17 calculate to be 33.12” while reporting to be 34.8” (close to 35 ok). To get to 35” you have to go to 37” tires

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[plex]

At this point, it is pretty much accepted that most tire manufacturers using nominal size in their product name, most 37s are a tad larger than 35", 35s are half inch larger than 33", while 33s are most likely 32".

A shitty "industrial standard" but it is what it is, it actually unintentionally prolongs the life of your axle, u-joint, brake, otherwise how your stock axle can handle a true 37 (which probably like a nominal 39/40).

 

[Arterius2]

Using Falken Wildpeak 35/12.50/17 M/T01 as an example. I tried this with KM3 and other tires to the same conclusion

There are 63360 inches in a mile. The circumference of a circle/tire is Diameter multiplied by Pie (3.14159265...). Revolutions per mile is thus 63360/(PIE x Diameter). This becomes 609 = 63360/(3.14159265 x Diameter). Solving for the Diameter we get Diameter = 63360/(3.14159265 x 609), which yields 33.117 inches. Thus your 35” tire is actually 33”. Even accounting for a manufacture’s website’s listing that the overall diameter is something like 34.8 inches, you are leaving customers 1.7” short of tire diameter.

For example: Falken’s 255/75/17 calculate to be 31.2”, but they report 32.3”. Similarly Falkens 35/12.5/17 calculate to be 33.12” while reporting to be 34.8” (close to 35 ok). To get to 35” you have to go to 37” tires

You fail to factor in the fact that tires deform and squish under weight, usually as much as 1-2”. The measurement you see in the specs are nominal sizes when fully inflated and under no load. Meaning floating in midair.

My tires measure 35.1” when off my Jeep and 33.5” when on my Jeep.

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