Speedometer Gear ?

Lee DeLaBarre Daytona62

Actually, it could be either or neither. Measure the diameter of the tire you are currently running and the diameter of the tire you are going to end up with. If the diameter is the same, the gear change is not necessary. If the new tire is bigger or smaller, you need to change the gear accordingly

Lee DeLaBarre Daytona62

It's about 2 inches shorter .

If I'm not mistaken, more teeth for smaller diameter tires... since the car goes lesser distance for each revolution we want the driven gear to spin around slower for each revolution to reflect the slower actual speed.

But, what's the hurry? Put the new wheels and tires on and then figure out how many fewer or more teeth based on your speedo reading in relation to your actual speed. I think it will be a direct relationship, eg, if the speedo reads 60 when you are actually doing 54, the reading is 10% high, and you probably want 10% more teeth on the driven gear (the one attached to the speedo cable), so if it had 30 teeth you want to change to 33 teeth. You may even find that the speedo isn't accurate now, before making the wheel & tire change, if you check the speedo against highway mile markers.

Actually, that is pretty much what I do to check mine only I use my GPS and check the indicated speed against the GPS's indicated speed and correct accordingly. I also then like to go on a 40 mile interstate drive and check my odometer against the mile posts over that distance to see if the speedo and odometer are BOTH correct.

I would not buy any pinions or make any changes until the tire/wheel swap is complete and you can take it out on the open road and really find out what the error is and what is needed to correct it

Lee DeLaBarre Daytona62