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[ihc] Formulaic revolutions



Ed,

I found my notes from talking to Goodyear.

I'd asked them about a LT235/85R16 truck tire.  They told me 657 rev/mi
which works out to an effective  diameter of 30.71 inches.  If you take the
std formula for figuring the diameter of a tire you get 31.73 inches.

The section width of this tire is 235 mm.  235/25.4 = 9.25 inches.
Height of the tire section is 9.25 * 0.85 = 7.86 inches.

The dia is (7.86 * 2) + 16 = 31.73 inches

That's about a 3.3% difference.

Steve
That's 'cause rev's/mile is based on the static loaded radius of the tire, not the 'free' dimension as measured. An 8-10 ply 235/85 doesn't give up as much dia. as a flotation size(typically at 'normal' pressures). As noted, rim width also affects SLR.

Jim



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