Tire sizes can be a bit confusing, as the size designations changed a lot over the years. From standard bias ply sizes such as 6.70-15 to Alpha Numeric sizes like F70-15, all the way up to modern P-Metric sizing, such as 205/75R15. Even the most savvy car guys have trouble decoding certain sizes, so take a look at this handy chart, and it should help you figure out the bias ply and radial tire size cross reference!