tire size vs speedo ?

Yes and i learned the hard way. I had a 95 v6 with 15 inch wheels. I put on a set of 17 inch GT rims from a 95 GT. Well i was going 61 i thought in a 55 and the officer said i was going 65. This is when i figured out that the speedo was off and other confirmed this would do it. I dont know how u correct it on the newer stangs, probably with a reflash of the computer i would say but dont know for sure.

The tuners have adjustable parameters for tire up sizes and gear changes. I just did mine for the 4.10's. Was reading 80mph when actual speed was 60mph. I read the tire change is minimal though. You can play w/ this. http://www.miata.net/garage/tirecalc.html

mrsxty52u said:

I took off my stock rims and tires and put on 17" wheels and tires.will this affect an acurate reading on my speedo?

Click to expand...

Only if you change the over all tire size (outside diameter)... What's your new tire size?

Here's another calc you can try.

http://www.angelfire.com/fl/procrastination/rear.html

GTYUP V8