Whats the best way to accurately recalibrate the speedo when you run different wheel & tire heights. I really hate the fact that my car shows extra miles on it since I'm running a shorter wheel & tire package. Can the dealer or anywhere else recalibrate the speedo???

 

Typically with a UniChip style car computer you can do that... I haven't heard of anyone doing that on a TL. I had a Chev s-10 ss prior to my TL and I know there was a plug in computer that would be able to claibrate wheel diameter, in result fixing the speedo problem and tach reading..

but correct me if I'm wrong, with the wheel diameter larger the car would show that you are traveling slower than you actually are. Because if the circumfrence of the tire is larger, in one full rotation of the tire the car would travel further.. So that is a positive result on your tach, the car travels (example) 5feet according to the computer - one rotation = 5 feet .....but your car actually travels 5.5 feet in one rotation - so you are traveling further than the car is reading you are traveling... resulting in less miles on the car by tricking the car......

Another thing to look at is your speedo..the speedo won't be accurate it will say you are going slower than you actually are...so I would reccomend driving side by side with a buddy and talk to him on your cell phone and find out what speed he is going and compare it to your speedo... Don't expect too much difference, Tatewaki did the calculations for his wheel/rim combo on his car, they were off stock size by a little but the result on the speedo would be something like 1km off for every 100km. so it wouldn't be even close to something to worry about, with regards to driving the limit on your tach and having a cop radar you at +10miles..

 

Thanks RF, Yeah if I had a larger than stock diameter, I wouldn't even consider it at all (free miles ;-) but I went from 50s to 45s and I can tell the speedo is showing high by about 5% or so. Not a big deal, I just thought there might be an easy way to have it corrected at a speedo shop or something. They may have one of those plug in computers that you mentioned.