I have a 1982 TA that needs new tires. The previous owner replaced the factory rims with an Epsilon racing rim package and the car currently has BF Goodrich Radial TAs that are size 245/50VR15. The outer diameter of these tires are around 24.7 inches.

What I am trying to do is match the original tire diameter for the car which I believe was 25.4 inches based upon a standard rim of 14 inches. Although I haven't tried to calibrate it the speedometer seems close enough but may actually be reading high based upon the difference in wheel sizes. I am not sure whether the car came with a 14 inch or 15 inch rim.

I would like to keep the rims and I have a good quote for replacement 245/50R15 tires. But it would be nice to have something on the rims that more closely match the original tire diameter so that the speedometer is accurate.

Thanks in advance!

 

TA probably came with 215/65-15 tires. To match them diameter wise you will want a 235/60-15

 

Thanks ME!

I was able to verify the tire size you gave me. That was a big help. And the new 235/60R15s will be much cheaper than the 245/50R15s that I would have had to buy from Dunlop.

I calculated a difference in speedometer readings at 60 mph to be 64 mph with the the smaller tire.

You were a big help.

 

Ok, I put the 230/60R15s on and they look great. I should have analyzed the speed before though. Now when the car is doing 70 according to the speedometer, it is actually doing 64. This is not a big deal, but it does put extra miles on the car.

So my question is can I change out the speedometer or the gear in the transmission to get the speed right? I am now almost sure that the car probably came with 14 inch rims when new. And I know that there was a 15 inch option. So is there a different speedometer for each option? Or is it done through the rear end gearing? Or is there a different gear in the transmission?

I have a 4-Speed 76MM transmission.

Thanks!