Sry for yet another gear thread but when i did a search i got too many hits. Anyway, i just fixed my speedo and its off by 10-15mph so im wondering if one of the previous owners mightve swapped gears. What the calculation where you can rotate the driveshaft (or was it the tire?) and count the number of rotations it takes to turn the tire? Also, does a bigger then stock tire have any effect on this calculation?
gear calculation
- Thread starter GT89Mustang
- Start date
04sleeper
Founding Member
Rotate the tire once and count the number of times the driveshaft rotates. 3 times= 308, 3 1/2 times= 355, 3 3/4 times= 373, etc.....
Tire size will not change how many times the tire rotates so you will still find out what gear you have but it will have an affect on the spedometer being off.
Tire size will not change how many times the tire rotates so you will still find out what gear you have but it will have an affect on the spedometer being off.
Oh, yeah, bigger diameter tires
will have several mph difference if it's an inch or more.
Check out www.SMOKEemUP.com for some good speed calculators, they even have the AOD ratios in their database and calculate speed per rpm, tire dia & ratio.
That might help you figure out where you're at.
Also, do a search for speedometer calculators, I forget where they're at right now. They'll tell you what number of teeth in your speedo driven gear you need for your gear ratio and tire dia.
will have several mph difference if it's an inch or more.
Check out www.SMOKEemUP.com for some good speed calculators, they even have the AOD ratios in their database and calculate speed per rpm, tire dia & ratio.
That might help you figure out where you're at.
Also, do a search for speedometer calculators, I forget where they're at right now. They'll tell you what number of teeth in your speedo driven gear you need for your gear ratio and tire dia.
