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Old 03-16-2021, 06:25 PM   #5
porschefan76
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Join Date: Feb 2020
Location: Coastal NJ
Posts: 71
Garage
Hey all. Not to be too big of an math nut on you here, but 1 mile every 40 miles isn't really unreasonable. For my 265/35R18 rear tire, with ~8/32 to 10/32 of tread depth throughout the life of the tire, I did some of the math and just the theoretical change in circumference of the tire over it's life would result in an additional 0.81 miles per 40 miles on a "worn out" tire (2/32" of tread depth remaining) compared to a new tire. I think adding in the fact that the Boxster came with different diameter wheels wearing different section width tires, that'd be within the realm of engineering accuracy? What really baffles me is that my 01S seems to always indicate 4 miles per hour faster on the speedo than whatever speed I am doing. How that magic happens, I'm not sure, because the speed differential should be proportional to vehicle speed if it's based off of a sensor and an algorithm.

Anyway that's just my two cents.
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