Tires 101

You find your tire size on the side of your tire. You'll see a number like P215/55R17 97V. The 215 is the width in mm, 55 is the aspect ratio and 17 is the diameter.

What the Numbers in Tire Sizes Mean

The numbers in tire sizes represent the width in mm, aspect ratio, and diameter in inches. There are also numbers and letters representing the type of tire, construction type, load index, and other details.

It's easy to find your tire size on the side of the tire, but it is a good idea to double check the information on the side of the tire you are replacing, with the vehicle manufacturer recommendations.

Using the following sidewall marking cheat sheet, we can investigate what does P215/55R17 97V tire size mean.

P = Passenger car tire

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. Be sure to review our article on how to check your tire treads.

215 = Section Width, or Tread (mm)

The section width is the width of the tire from one sidewall to the other measured in millimeters.

55 = Aspect Ratio

Aspect ratio is the ratio of sidewall height to the width of the tire in a percent. The height of the tire is 55% of 215 mm, or 118.25 mm (or 4.65 inches high).

R = Radial

This means the layers run radially across the tire. instead of say, a bias-ply tire where the plies are crossed.

17 = Wheel Diameter

Wheel diameter is the size of the wheel that the tire is intended to fit on.

97 = Load Index

Load Index indicates the maximum load carrying capacity of the tire. It is very important to only install tires with a load index that meets or exceeds your vehicle manufacturer’s specification.

V = Speed Rating

The speed rating designates the maximum speed at which a properly installed and inflated tire can be driven on. In this example, the speed rating is V which means it can be driven at speeds up to 149 mph (240 kph).

What 225/50R17 Means

The number 225 identifies the tire section width (the measurement of the tire from sidewall to sidewall in millimeters). This tire has an aspect ratio of 50 means that the tire's section height is 50% of the tire's section width. R indicates the construction used within the tires casing, in this case "radial construction."

The Difference Between an Exact Match and a Compatible Alternative

An Exact match means the tire your looking at has exactly the same characteristics proposed by the manufacture of your vehicle, while a compatible alternative may have a higher load index or higher speed rating.

Exact Match

An Exact Match means that the manufacturer proposed tire for your vehicle has exactly the same characteristics as you entered in your search. The section width, aspect ratio, rim diameter as well as the load index and speed ratings match exactly.

Compatible Alternative

These are tires which may have a load index that is higher than what you have entered in your search, or a higher speed rating. These tires are compatible and it is safe to replace tires with those having a HIGHER load index or a HIGHER speed rating.

Tire Size Checklist

Always check the size molded on the side of the tire against the information on the sticker on the inside of the driver's side door post to ensure you are buying the size of tire intended for the vehicle. If you're trying to find your tire size, here's a handy checklist to get you started:

Check your tire sidewall and note down the series of numbers, and the alphanumeric symbols after the size. For example, P215/55R17 97V, or LT265/70R17 LRE in the case of a light truck tire. Compare this information to the tire size information on the driver’s side door jamb. On most vehicles, there is a sticker displaying the tire size that came fitted on the vehicle from the factory. In older models, and a few European vehicles, the original tire size could be on a sticker on the wall of the glove box, or on the inside of the fuel tank hatch. Can’t find the sticker on your car door? The owner’s manual is another good place to go for information on your tire size. The manual typically has the recommended tire size for all the different trim levels of the vehicle’s make and models.

Need Help With Your Tire Size?

If you need help finding your tire size, give us a call toll-free at 1 833 885-8575 and our friendly customer service agents are there to assist you.

The main benefit of new tires is safety. Driving on worn out, bald tires is an accident waiting to happen- especially on wet roads. The National Highway and Traffic Safety Association (NHTSA) estimates that 26% of vehicle accidents involve tires with insufficient tread (less than 2/32nds of an inch).

Why driving on excessively worn tires is a safety factor?

1. Hydroplaning: The grooves in the tread provide space for water to be channeled out from under the tread. These and other features in new tires provide grip in rain, snow and ice. With shallow tread, the vehicle becomes very difficult to control on slick roads. 


2. Excessive heat build-up: Driving creates friction between the tire and the road’s surface which creates heat.  Treads allow air flow between the grooves which helps to cool the rubber in the tread area of the tire. When the tread wears down, there is less airflow around the tread and this causes more heat to be retained in the tire. High temperatures are unsafe because it can cause a blowout.


3. Loss of air pressure/flats: With worn or bald tires there is less rubber to protect the tire from penetration by foreign objects like nails, screws, glass or even wire. If you travel on gravel roads, the risk of a flat due to worn tires is even greater.

A set of new tires address all of these safety risks, and will give you more confidence and control behind the wheel.