How accurate is your speedometer?

[NeedForSpeed]

Originally Posted by Huskymaniac

Well, not for me. That would correct for about 1.8% of the error but my speedo is off closer to 5%!

So you don't get tire rub with tires that are more than 13mm larger in diameter and 10mm larger in width? That would be good to know as it would allow me another option for snows. Up until now I have only looked at 205/55/16 and 225/50/16.

Tony,

I don't understand how the speedo/odometer work. Interesting, in using this site to calculate and compare my 3.70 geared 235.40/18 tires with stock 3.545 gears and stock 225/50/16 tires, both in 0.694 4th gear (love this site)
http://www.kabamus.com/garage/gears.html

Comparing stock tires, 3.70 to 3.545 ratios, 4th gear, the calculated speed increase with 3.545 gears at 2000 rpm is 2.57mph, 2500 is 3.22mph, 3000 is 3.86mph, and 3500 is 4.51 mph (103mph vs 107.51 mph).

Now, factoring my tire change:
3.70 gear with 235/40/18 at 3000 equals: 88.29 mph
3.545 gear with 225/50/16 at 3000 equals: 90.18 mph,

so, I"m slightly less than 2 mph less in 4th at 3000 rpm, compared to 3.86mph different comparing the same gear change and stock tires.

At 2000 rpm, my big tire 3.70 are only 1.26 mph slower than stock tire 3.545 gears, 58.86mph vs. 60.12 mph.

What all this has to do with speedo/odometer factory calibration, I don't know, but the numbers are fun. We run 3.545, 3.70, 4.111 and 4.444 gears in our SVXes, so the website helps sort out gear and tire changes.

For snow tires on stock rims, you could certainly use 215/55/16, 97-spec.

Tire rub depends on the tire size and tread width (different models of same size tire have different tread width), and wheel offset. My 18" '07 Lexus wheels are 10mm closer to the fender than OEM wheels.

I can get all fingers between the TOYO VERSADO LX rear tires and the wheelwell .