Tire Conversion Help by Greg Zyla

Q: Greg, I enjoy driving my 1973 Chrysler Newport. The sticker on my door well calls for a minimum of an H7815 tire and I want to meet or exceed the minimum because this car is big and heavy while trying to maintain speedometer accuracy. Is there a conversion chart available to help me? Cliff W., New Port Ritchey, FL.

A: Sure is Cliff. First, I’ll tell you that the H7815 equates to P225/75R15, and there are several sites on the Internet that provide conversion tables for you to check other sizes. One such site is http://www.tirerack.com/tires/tiretech/45_conversionchart.html - so go ahead and check out other sizes. I’m glad you are aware that if your put larger overall tires on your Newport, it could affect the accuracy of your speedometer and you’ll be going faster than the speedometer says by a bit because your final rear gear ratio would be a little higher, but lower numerically, from, say a 3:23 rear to a 3:18 with the oversized tire.

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