A Guide to Vehicle Wheel Sizes: It’s really important

Simply put, the bigger your tyres are, the more grip your vehicle will have on the road. As the width of the tyre increases, it can cover more of the road surface area.

Many drivers give little thought to the sizes of their wheels and tires except for cosmetic purposes. But, wheel size — and the size of tires you put on them — matter. Using improper tires can be costly and sometimes even dangerous.

Does Tire Size Really Matter?

Simply put, the larger your tire, the more of a grip your vehicle has on the road. As a tire’s width increases, it covers more surface area on the road. According to iSee Cars, this increase in contact with the pavement gives your vehicle more to hold onto, increasing its handling and ability to maneuver.

So, does tire size really matter? The short answer is: Yes. But does wheel size matter? It depends.

Wheels and tires are not interchangeable words. Tires are a part of the wheel setup. For instance, your vehicle has a set size of rims, but you can buy different sizes of tires to fit those rims, as long as the middle of the tires is the correct size. That being said, a vehicle with bigger rims will often be able to fit larger tires than other vehicles.

Bigger Wheels = Bigger Bills

Overall, bigger tires and wheels are better for increasing your vehicle’s traction. However, bigger tires also mean bigger price tags, according to Consumer Reports. Try to find the best balance between size and your budget. If you opt for larger wheels when you purchase your vehicle, you may not see this rise in price at first, but when you have to replace the larger wheels and tires, you will have a higher cost of replacement than someone driving a vehicle with smaller wheels.

Once you choose a tire size for your vehicle, you’ll want to stick with that size when you buy replacements. The reason for this is that a differently sized tire can confuse your speedometer and even cause damage to your vehicle’s anti-lock braking systems and stability system calibrations. This applies to switching to both smaller and larger tires. Changing to larger tires with an improper sidewall height can cause damage to your vehicle’s suspension system, wheels, and the tires themselves, and can run the risk of incorrect speedometer readings.

However, if you match larger-diameter wheel sizes to lower-profile tire sizes, your speedometer and odometer shouldn’t see any changes. This setup means your tires have shorter sidewalls, which means stiffer sidewalls, and a higher chance for blowouts should you hit a pothole.

When you replace your tires, try to stick with the same brand and size, as mixing and matching leaves your vehicle with different tire threads, which can cause spinouts and control loss.

Tips on Buying New Rims and Tires

The average driver may not know exactly what they are looking for when they shop for new tires, but as long as you keep a few fundamental rules in mind, replacing tires and rims is easy.

How to Read Tire Sizes

When you look for new tires, you’ll come across size names such as 235/75R15 or P215/65R15. These labels can be confusing if you’re not sure how to read them, but once you learn the language of tires, they become more clear.

On the left side of the slash symbol, you’ll find three numbers and sometimes letters. The numbers represent how wide the tires are, in millimeters, from sidewall to sidewall. The bigger this number is, the more road the tire touches.

If you see a letter on the left side, it refers to the tire type. Letters you might see are:

• “P,” for passenger vehicle tire. This letter also lets you know that the tire is made to meet standards in the United States. When there is no letter, it means it’s made to meet European standards. The two types have different load capacities.
• “LT,” for light truck. Tire sizes that start with these letters are intended to be used for light trucks. They’ll have higher psi recommendations to better take on trailers and heavy loads.
• “ST,” for special trailer. Tires sizes with these letters are for trailer wheels only.

Using a P215/65R15-size tire as an example, we can tell that the tire is for a passenger vehicle and has a 215-millimeter width.

On the right side of the slash symbol, you’ll find two numbers, a letter, and two more numbers. The first set of numbers represents the aspect ratio of the tire’s height to its width. In our P215/65R15 example, those numbers are 65, which means the tire’s sidewall height is 65% as large as the tire’s width. The middle letter on the right side of the slash tells you about the tire’s construction method and will most commonly be “R,” or radial. This means the layers of the tire run radially across it.

The last number is important, as it tells you what size wheel the tire fits. In our example, this number is 15, which means the tire fits a wheel with a 15-inch diameter.

More Tips

• Rayone  explains that sometimes, it’s acceptable to have differently sized tires and rims for the front and back wheels, which is called staggered tires. You’ll most often see this with muscle cars, such as the Mustang, Challenger, and Camaro. The reason this works is that the rear wheels don’t have to turn like the front wheels do.
• The larger your rim, the more difficult and expensive buying new tires will be. Once you start using large tires, you may find that only a handful of tire manufacturers make your size. However, this problem is generally avoidable with the average vehicle in car dealerships.
• Large wheels generally mean thinner tires. The tires have to be small enough to fit inside your wheel well. The thinner your tire, the less able it is to take on rougher roads and potholes, which can lead to blowouts.

Wheels and tires are important components of your vehicle. Though that may seem a little obvious, many drivers don’t give a second thought to the tires they choose for the cars, which can lead to many unwanted problems. Know your car and avoid making dire tire mistakes to ensure your wheels are safe and are giving your vehicle the best levels of traction possible.