Quote Originally Posted by wayde View Post
I recently got ahold of a set of 4 lug 15 in rims off of a chevy cobalt. I removed the 14 in 185 tires and replaced them with these rims with 195 tires. I believe this change has caused my speedo to be off. Any math majors out there that may be able to tell me what variance I am getting from stock setup. Also is there anything I can do to tune computer to account for this variance. Please Advise.
There probably will be a slight variance, but I wouldn't know how to calculate it. I had a similar situation with a Celica I used to own. The speedometer read several MPH higher than my actual speed. It didn't bother me much as the tires were far superior to the original ones of the specified size. The only way to know for certain is to try it. Also, don't forget that any variation will also affect your odometer reading. I found that to be more of an annoyance than the speedometer being off.