View Here : Tire Size Explained
The first letter on a tire indicates the tire’s class. P designates this tire as a passenger car tire, an LT before the tire size would mean the tire is a light truck tire, and a European metric tire would have no letter before the tire size.
Bike Tire Tube Sizes Explained Erica Leigh Different types of bicycles use different sizes of wheels. ... Look for the right tube size based on the tire and wheel’s given measurements, not your own measurements, except when neither the tire nor the wheel indicates its size.