I've got 315/75r16 Coopers on now which come out to about 34.5", but before I had 29" or 30" tires. I have a '97 so to correct the speedo/odometer is much more of a PITA than just getting a programmer or taking it to the dealership. So I was just wondering how I could calculate how far I'm actually traveling, or how much of a difference there is? I know its a bit further than what the odometer is really saying, but I'd still want to go as close to as exact numbers as possible.

btw, I've 3.55 gears if that makes any difference.

 

If you had 29” tires you actually travel 1.18 miles per every mile your odometer shows
If you had 30” tires you actually travel 1.15 miles per every mile your odometer shows

 

You can get the differences yourself quite easily from the following site.

http://www.discounttire.com/dtcs/infoTireMath.dos

In this case the gear ratio does not matter as you are not changing it.

 

I went from stock size which was around 31" to 35" and when my speedometer said I was doing 60 my GPS said I was doing 64-65 so your stock speedo might be a little off to but gives you an idea

 

Thanks guys, I searched a little before but couldn't find much besides the gear ratio calculation and what not.

aPINCHbetter90, My speedo is off about 5 when I'm going 40-45, but after 50 mph it increses, and by 60-65 I believe its off by nearly 10 mph. I'd say keep that in mind as you drive, but you have a nice GPS to help you out

Thanks again guys