For your 1965 (or 1962s to 1965's) A. Divide 63.36 by the car's tire circumference. The circumference is tire diameter times 3.14. (e.g.,a 26 inch tall tire has 81.64 circumference so 63.36/81.64 = .776 B. Multiply that result by 8 (8 x .776 = 6.208) C. Multiply that result by your axle ratio (e.g., 3.23 x 6.208 = 20.05) The result is the number of teeth needed on your car's speedometer pinion, or 20 in the example above. Gary H. Bill wrote: ... > I'm trying to find info on how to convert modern tire sizes > (215/75/14) to the old sizes (D75-14). I ultimately want to figure out > what is the correct speedo gear is for my current setup.... ---- Please address private mail -- mail of interest to only one person -- directly to that person. I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic. Thanks! '62 to '65 Mopar Clubhouse Discussion Guidelines: http://www.1962to1965mopar.ornocar.org/mletiq.html.