View Full Version : 245 50-zr16 tires

10-20-2003, 09:38 AM
Is there any way to re-calibrate the speedometer for these smaller diameter tires? My speedo reads about 6mph faster than i'm actually going with these tires.

fast Ed
10-20-2003, 10:42 AM
The difference you need on the speedo gear is about 3/4 of a tooth. So if you go up the next step to a 21 tooth, your speedo will read a bit too low, probably by about 3 mph. Your choice ... ;)

Take a look at the speedo gear calculator here:


I'm not aware of any other reasonably priced method to correct for this ... anyone else ?

Ed Nicholson

10-20-2003, 12:41 PM
3 mph over... hmm... that's not so bad. just have to watch my speed a little more. Is it easy to change the speedo gear? can you access it outside the AOD?

i just got these tires replacing the other set of 245's i had. i wanted 255's but no popular tire merchants have them. i replaced the 245's because of an emergency- almost blew my left front from alignment issues. i always change all 4 of them if one blows due to handling issues.

Ed, what kind of tires/wheels are on your SC? love the thick stance.

fast Ed
10-20-2003, 01:50 PM
The speedo driven gear is on the end of the speed sensor, which goes into the left side of the transmission case. Pretty easy swap once the car is in the air.

In the small avatar pic under my user name, my car has 275-40-17 Hoosier track tires on 17x9 2003 Mustang Cobra wheels. If you look at the pics on my member page, it's wearing 255-45-18 GoodYear Eagle F1 GS-D2 rubber on Fittipaldi Force 18 x 8-1/2" wheels for the street.

Ed N.