Tires explained

On the Road 4 min read

How often do you think about your tires? While perhaps not the most interesting or engaging aspect of car ownership, tires are crucial. All things considered, tires are the most important aspect of your vehicle’s performance and safety. Tires maintain a car’s entire ability to move and to be controlled, and without tires your car is useless. Poor tires don’t just limit performance, but they also pose a serious and easily avoidable risk to you, your passengers, and others on the road. The following will provide you with a base knowledge for understanding the tire requirements for your car, how to care for your tires, and when it’s time for a new set.

Decoding a car tire label

Tires come in many sizes and specifications and it’s of extreme importance that you are using tires that are compatible with your vehicle. The tire sizing information will be printed on a sticker or plaque located on your vehicle, generally on the inner panel or pillar of the driver’s door. This plaque will define the size of tire required for your car as well as the tire’s load requirement and optimal inflation pressure. For the purposes of an example, here’s a hypothetical tire size: 215/50R17 91H. That collection of numbers and letters is the sizing specification for a tire; let’s break it down.

  • 215: The width of the tire in millimeters
  • 50: The height of the sidewall shown as a percentage of the width of the tire (so this would be 50 percent of 215 mm)
  • R: Radial (a common type of modern tire)
  • 17: The wheel diameter in inches, in this example the car is using 17-inch wheels
  • 91: Load rating for the tire, which describes the amount of weight that the tire is designed to support. This number must match or exceed that required by your vehicle.
  • H: The tire’s speed rating (can be from L to Z, with “H” indicating a maximum speed of 130 mph)

This format of sizing is standard across most passenger vehicles and, providing you haven’t changed the wheel on your car for something other than what it was delivered with when new, you can always follow the manufacturer’s tire sizing requirements. If you are unable to find this information on your car or believe your car has aftermarket wheels, please consult a tire shop or the manufacturer of your vehicle to confirm the proper tire sizing.

Proper tire maintenance tips

With a proper set of tires on your vehicle, you’ll find that all aspects of the vehicle’s performance will be maximized. Many standard family-car tires can last up to 70,000 miles, but only if they are properly maintained and cared for. Thankfully, tire maintenance is both simple and straightforward.

  • Proper Inflation: This is no joke; an underinflated tire will wear out faster, use more fuel, and provide less grip. If your car doesn’t have a tire pressure monitoring system, buy a $10 tire gauge and check your tire pressure once a month when the tires are cold (warm tires will report higher-than-actual pressure as the heat expands the air inside the tire). You can find the optimal pressure for your car listed on the same plaque that displays the sizing information mentioned above.
  • Look for damage: When checking your tire pressure you should also check your tires for visible damage, including cracking, warping, or anything stuck in the tire itself. If the tire is damaged, consult your local tire shop immediately.
  • Alignment: If your car’s alignment is off (meaning your car does not drive in a straight line when the steering wheel is at center) then your tires will not wear evenly. Have your alignment checked if the car pulls in either direction or if your tires show uneven tread wear. Proper alignment will ensure you get the most from your tires and that they perform as intended.
  • Rotate your tires: When you buy new tires, the shop will tell you when they need to be rotated, usually at no more than 6,000 miles. If the shop does not provide a window sticker to remind you, make a reminder in your calendar to have your shop check the tires at your next service interval. Proper rotation greatly extends the life of your tires and many shops include free rotation as part of the cost of having your tires mounted when you buy them.

Understanding tire tread depth

Even if you nail all of the above tire care points, eventually your tires will need to be replaced. Assuming your tires were spared any damage or uneven wear due to the above-mentioned scenarios, the main concern will be tread depth. As a tire is used, the rubber slowly wears away, lowering the tread depth of the tire and limiting the tire’s ability to grip the road. Tire tread depth is expressed as fractions of an inch, generally 32nds. For winter driving, experts recommend 7/32nds of depth on the tread and 4/32nds for non-winter months. At 2/32nds, the tire should definitely be replaced.

There are a few ways of measuring your tread depth. First, you can buy a tread depth gauge, which will give you a cheap and accurate measurement of what is left on your tire. If you don’t have a gauge or are in a pinch, you can also measure your tread depth using an American penny. The top of Abe Lincoln’s head is 2/32nds from the edge of the penny, so hold Abe head-first into the tread of the tire. If you can see the top of his head or his hair, it’s time to replace the tire. Finally, all new tires have wear bars that indicate when the tire is worn to the point of needing to be replaced. These are small rubber bars that run across the deeper grooves in the center profile of the tire. If your tread has worn down to the same depth as the wear bar, it’s time to replace the tire.

When you do replace your tires, have it done by a qualified tire shop and never install mismatched tires on the same axle. Replace your tires in pairs and be sure to make note of the rotation schedule for the new tires. With some simple care and a watchful eye, your new tires will last longer and provide you with the performance and safety you need to get the most out of your car.

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