Understanding Tire Sidewall Markings
Somewhere on every tire’s sidewall will be small printed or pressed type. This is part of what is called the sidewall markings. Sidewall markings include important details you need to know about:
- Tire construction materials (e.g. Polyester, steel, and nylon with vulcanized rubber)
- Tire construction type (e.g. Radial Tubeless)
- Tire size designation
- U.S. D.O.T. Compliance followed by the Tire Identification Number
- Road conditions the tire is approved for (e.g. M+S = Mud + Snow)
- North American Load and Pressure Marking
These abbreviated terms are called tire codes, and you can find out more about tire code here. For the purposes of this post North American Load and Pressure marking and Road Condition Markings are what we’re the most interested in. This will tell you the max load, and max pressure to which you can inflate your tires, and whether or not your tires are rated for Snow or adverse driving conditions.
Tire pressures are measured in PSI (pounds per square inch). Don’t inflate your tires to the maximum pressure!
Inflating your tires to, or over, the maximum pressure will lead to catastrophic tire failure (usually called a blowout). How quickly that happens depends on the current age and condition of your tires – it could happen right away or while you’re on the freeway at speed. Blowouts account for a small portion of major road collisions and fatalities each year.
Being conscious of your vehicle’s maximum safe load and proper tire inflation are important. Cramming fifteen people into a Passat might seem like a fun experiment when it’s parked, but you don’t want to take it on the road with that much weight. Take extra care when moving or hauling a trailer, for the same reason.
It’s best to keep two sets of tires for your vehicle; winter and warm-season tires. Winter tires are formulated so they have better traction in freezing conditions and on icy or slippery surfaces. The rubber and vinyl used in warm-season tires loses important traction when it gets cold, becoming harder and more subject to failure.
On the inside door frame of the driver’s side door you’ll find an engraved metal plate with the type of tires you should buy. If the type of tire listed here, and the tires you’re planning to buy match, then the manufacturer says you’re safe to use them. This plate will also tell you the pressure you should inflate your tires to for optimum safe driving.