 |
Preventative Maintenance
Tire Sizing & Tread Wear
Tire Sizing
Passenger Tire sizing is typically displayed as: P215/65R15 89H
- The "P" stands for "P-Metric" or "Passenger". This means that it is a North American tire sizing designation. European tires usually don't have the "P" attached to the size.
- Tires with higher ply ratings will generally start with "LT" which stands for "Light Truck". This indicates the tire will always have a Load Range indicated. Always use LT metric tires on vehicles that call for it. Never substitute a P metric tire for an LT metric tire, even if all the other dimensions are the same.
- "215" is the width of a tire, also known as the "section width". This is the width of the tire in millimeters at its widest point from sidewall to sidewall when mounted on the recommended rim width. The actual tire width can vary depending on the rim width it is mounted on.
- "65" is known as the Aspect Ratio.
- The "R" stands for Radial, meaning it has a radial construction. Radial tires have ply cords that extend to the beads and are laid at 90 degrees to the centerline of the tread. Other possibilities include "B" for belted construction and "D" for diagonal construction. This means the ply cords extend to the beads and are laid at alternate angles less than 90 degrees to the centerline of the tread.
- The "15" stands for the diameter of the wheel in inches. This is the exact size that this tire will fit. There are some older rims called "TRX" which are metric measurements like 390. You absolutely cannot mix TRX rims with regular tires.
- The "89" is the load index.
- The "H" is the speed symbol.
Tread Wear Indicator
How do you know when you need new tires?
As your tires wear down, their ability to grip the road decreases. Each tire has wear bars. These appear at various points around the tire as bars running through the tread design from one side of the tire to the other.
When your tires are legally worn out, the tread will be at the same level as the tread wear indicators, and will be easily visible. Usually before the tire gets to this point, they will begin to feel unsafe. Do not wait for them to get to the wear bars. Just because the tread depth is not as low as the tread wear bar, it does mean it is safe.