Basically my question revolves around how the cars trip computer / odometer calculates the distance that the car has traveled. I would assume that there is a sensor on one of the axles or some such that measures the number of revolutions made.

However does that mean that this would make the trip computer / odometer inaccurate if you put different size rims on.

For example 1 revolution on 15" rims will not propel the car the same distance and 1 revolution on 16" rims, or any other size for that matter.

I could be way of here and the computer could calculate it some other way but basically i was just curios as the what the answer was here.

1 revolution of a 16inch rim will take you further than one of a 15inch - if there are no tyres on the rims

when you step up size of your rims, you have to bring the profile / sidewall of your tyre down - to keep the overal rolling diameter of the wheel and tyre combo within a specified limit - i *THINK* its around 1inch is what you can change the rolling diameter/ circumference.

hope that helps somewhat

Provided the rolling diameter remains similar to the previous set of wheel and tyre, it won't affect the trip computer. If the rolling diameter did change significantly, then your speedo would be out too, which is illegal for obvious reasons.

http://www.miata.net/garage/tirecalc.html

Ah of course. :doh:

Didn't even think of the speedo. But assuming someone put like 20" rims or something on then surely it would sill be a larger circumference even with low profile tyres so there must be some way to adjust it.

Not actually thinking of putting 20s on just curious.

:Edit:

Apparently not according to the tyre calculator, cheers Tuff

Ah of course. :doh:

Didn't even think of the speedo. But assuming someone put like 20" rims or something on then surely it would sill be a larger circumference even with low profile tyres so there must be some way to adjust it.

Not actually thinking of putting 20s on just curious.

:Edit:

Apparently not according to the tyre calculator, cheers Tuff

NP's
Basically using that, Most tyre combos on a magna will not change that greatly as to differ the speedo that much that you will get a speeding fine every time you pass a radar.