I recently bought the car, and with it came 205/55/16 tires instead of 245/50 which threw my speedo off. Also lastnight I found out that the car origanally came with 2.73s (it has 3.42s). So my question is, is there a tires size that would fix both the of these problems. I know if I got to a 245/50 tire, that the tire prob would be fixed, but how much taller should the rear tire be to fix the gear prob? Or is it easier to change the speedo gear (if y'all have one, my old Tbird did, and when rearend ratios were changed, that had to be changed too). Thanx for all your help, and sorry for the stupid question. I'm just trying to learn.
Wes 87 Iroc 305TPI

 

your not going to be able to accomplish that much of a correction to the reading by just changing tires. You effectively need a tire that is 20 percent taller (and that would effectively kill any benefit of the lower gear).

In short, your going to have to change the speedo gear. And, your probably going to need to change the driven and the drive gear (which requires the tailhousing of the trans to be removed).

 

yeah just change out your speedo gears, you can call your local dealership, and just let them know what your rear end gear, was and what it is now. And they can give you the right gears.

 

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go to the hp calculator