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RedDevil · 03-08-2018, 06:55 AM

By the way, there should be no difference in distance reported between new and worn tires, even though the new tires have a slightly larger circumference.

Amazing, no?

Consider this: A tire on a car is not a perfect circle. The contact patch is flattened out, and there the tread shrinks; the grooves narrow as the lugs get squeezed together.

By and large the distance a wheel travels with each rotation is the same as the length of the steel belts in the tire. The distance between the belts and the tread surface has no influence; again, the contact patch is flat.

Actually, if anything it is the other way round.
As my tires wear I see a very gradual reduction in the reported distance of my commute on the odometer. The same route that was 35.6 km when the tires were new now takes just 35.4 km.
I bet the belts have been stretched ever so slightly.

Worn tires slightly underreport the mileage.

03-08-2018, 06:55 AM	#7 (permalink)
RedDevil Master EcoWalker Join Date: Dec 2012 Location: Nieuwegein, the Netherlands Posts: 4,004 Red Devil - '11 Honda Insight Elegance Team Honda 90 day: 56.53 mpg (US) Thanks: 1,715 Thanked 2,252 Times in 1,458 Posts	By the way, there should be no difference in distance reported between new and worn tires, even though the new tires have a slightly larger circumference. Amazing, no? Consider this: A tire on a car is not a perfect circle. The contact patch is flattened out, and there the tread shrinks; the grooves narrow as the lugs get squeezed together. By and large the distance a wheel travels with each rotation is the same as the length of the steel belts in the tire. The distance between the belts and the tread surface has no influence; again, the contact patch is flat. Actually, if anything it is the other way round. As my tires wear I see a very gradual *reduction* in the reported distance of my commute on the odometer. The same route that was 35.6 km when the tires were new now takes just 35.4 km. I bet the belts have been stretched ever so slightly. Worn tires slightly underreport the mileage. __________________ 2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut. lifetime FE over 0.2 Gigameter or 0.13 Megamile. For confirmation go to people just like you. For education go to people unlike yourself. Last edited by RedDevil; 03-08-2018 at 07:57 AM..