That classic you’ve been restoring is just about done, and you just placed an order with us for some new chrome wire wheels. Now your attention turns to tires, because the last time this car had new tires, Neil Armstrong had just stepped on the moon. Not a problem. Today's tire sizes can be a bit confusing, as the size designations changed a lot over the years. As we get orders for our wire wheels, customers typically ask for suggestions on the proper tire size to match their new wheels.
So you wipe the dust off and look for the P number that you are so used to seeing on all the current tires. Problem is, you don’t see it. What you do see? 700-14. These are bias-ply. These tires used a slightly different sizing arrangement than the P-Metric scale used today.
Lets figure out what size is closest for your car because you want your speedometer to read a true value.
So, referring back to our original tire size of 700-14, with a quick calculation, we can see that an appropriate size that will be close to the original will be either a P195/75/14, or a P205/70/14.
To find whether the tire will “look right” or fill the original wheel well like the OEM tire did, you can calculate the overall height of the tire and see if it comes close to the replacement. In the example below, we will use a 16" tire that some Jaguar customers might use. All you need is the “P-size” of the tire. The formula to do this is as follows:
Even the most savvy car guys have trouble decoding certain sizes. This should help you figure out your bias ply to radial tire size cross reference!