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Discussion Starter · #1 ·
i thought of something. we all know about the speedometer thing, which isn't a big deal if you're off by 2 mph or something, but what about odometer? technically you could have driven your car further than your odometer says if you have really big tires. for examples sake, think of tires 1 mile in diameter; you would travel 3.14 miles for every tire rotation, yet your car would think you would have traveled less than 10 feet. on the other hand, and more importantly, if you have mexican tires that are like 12", you could end up "paying for" a lot of odometer mileage you didn't travel. and yes i think even 1" would add up to thousands of miles over the life of the car.

really, shouldn't the odometer be based base off of rpms, not miles? think about it, it makes more sense, because it would include idling, and the size of the tires would matter not.
 

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Discussion Starter · #6 · (Edited)
well, yes and no, because if you change the size of your tire diameter wise, you change how far the wheel would go when making a full rotation for every rpm. And if they set it at calculating distance by rpm, it still would be off when changed to a new wheel, due to the same concept of having different distance per rotation.
so you're saying that 3000 rpms with 15" tires will be a different speed/distance than 3000 rpms with 20" tires?

hmm had the same question but anyone know the speedometer differnce when going from 16 inch to 17?
google it, there are calculators that will tell you exactly. you input the exact tire sizes, and it tells you down to the fraction of a mph. i remember doing a calculation for fun, and using the same exact tire but going from 17" to 18", it was around 4%. so 2 mph if you're doing 50 mph.

may i ask why you have 16's on your car in the first place? si's have 17's. or are you doing 16" steelies for winter?
 
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