What to Look for When Buying Used Tires

Buying used tires can seem daunting to the uninitiated. Here are some tips to make sure you end up with quality, well kept tires.

Regardless of how many safety and performance features a vehicle has, their effectiveness is ultimately decided by the tires. That small patch of rubber at the bottom the tire is the only thing connecting the vehicle to the road. The thickness, condition, and type of tread (the pattern of raised bands that touch the road) determines how the steering responds to driver actions, how the suspension responds to curves, and the distance it will take to stop the vehicle. But before we look at how to buy used tires, let’s discuss some general tire information.

How to Read a Tire Sidewall

The sides of a tire are called the sidewalls. Each tire has two: the inner sidewall and the outer sidewall. If you look at a tire’s outer sidewall you will notice a big number stamped into the rubber.

Example: P215/50R17

  • The first letter denotes the type of vehicle the tire is made for. The most common are ‘P’ for Passenger Vehicle and ‘LT’ for Light Truck. The “P” at the beginning of the above example denotes that it is a tire for a passenger vehicle.
  • The three-digit number after the initial letter indicates the tire’s section width (the width of its cross section) in millimeters. Basically, the section width is the width of the tire is at its widest point. More specifically, it is the distance from the outermost point of the outside sidewall to the outermost point of the inner sidewall. In the example, the tire’s section width is 215 mm.
  • The second number (the number after the slash) is the sidewall aspect ratio. It indicates the height of the sidewall from the It is actually a percentage. – the ratio of how much of the aspect ratio tells us the height / profile of the tire. In our example, the sidewalls of this tire use 50% of the 215 mm section width. The higher the number, the taller the tire will be. So our ‘50 series’ tire is going to be a low profile tire, likely used on sports / performance cars.
  • The letter ‘R’ indicates that the tire uses a Radial type of construction. In a radial tire, the wires (typically made of polyester or steel) under the rubber tread that give the tire strength are laid out perpendicular to the direction of travel.
  • The last number is the diameter, in inches, of the wheel the tire is designed to fit. In our example, the tire is designed to fit on a 17-inch wheel.

What to Look for When Buying Used Tires in Canada

Tread Depth – The tread depth is the measurement, in inches, from the top of a tread to the bottom of its deepest valley. A typical new tire has a tread depth of 10/32 to 11/32 of an inch, and the minimum legal tread depth is 2/32 of an inch (meaning a tire with a tread less than 2/32 of an inch is not legal). A good used tire should have at least 5-6/32 of its tread depth remaining. You can easily measure the tread depth by inserting a quarter into the tread, caribou muzzle first. If the muzzle is not visible, then the tread depth is at least 6/32’s of an inch. If the entire muzzle is visible, then the tire has reached the legal minimum tread of 2/32.

A used tire with a tread depth of 6/32 should be able to cover around 10,000 km’s. It will also allow you to stop 100ft / 30m shorter than a tire with a 2/32 tread depth.

Tread and Sidewall Condition – A good used tire should have even treadwear (the tread should be worn out evenly), with no slick or smooth surfaces. The sidewalls should also be in good condition with no cracks, chips, or cuts. Look for wear rings in the sidewalls, as this will indicate the tire was driven when flat. Since driving on a flat tire can break down the structural integrity of the sidewall, pass on tires that show this type of wear.

Look for cracking between the tread blocks and where the tread meets the sidewall. You can push down on the tire and push in on the sidewall to expose hidden cracks.

Repairs – Look inside of the tire for signs of repair. If you see crude nubs of rubber sticking up, then the tire has been repaired with a ‘plug’. A plug is a piece of rubber that has been inserted in a hole in a damaged tire to repair the hole. A tire plug is less effective than a tire patch, and used tires with visible tire plug repairs should be avoided.

Age – To determine the age of a used tire, look on the sidewall near the bottom edge. Look for the letters “DOT”; to the right of “DOT” you will see a 4-digit number. The first two numbers indicate the week the tire was made (thus a number from 01 to 52), and the last two numbers indicate the year. You want to avoid used tires that are over 6 years old, because the oil in the rubber starts to dry out over time, leading to dry rot, cracking, and an unsafe tire.

When explained, the tire numbers make simple sense and give you a lot of information about the tire. If you follow these simple steps, you will be able to buy used tires that are not only safe, but offer great value too.