Unhappy with the wheels on your car? Hit the brakes on any improvements first and read below. There are a few things you need to consider before you upgrade the wheels on your car.

Upgrading Wheel Size

Changing the size of your wheels is one possibility. Keep in mind these factors when evaluating larger (or smaller) wheels for your vehicle:

If you plan to buy larger tires, you risk your new wheels and tires rubbing against components under your vehicle. Be mindful of the space available in your wheel well.
The size of your new wheel and tire can also change the gearing ratio, which has important ramifications especially for your vehicle’s anti-lock brake system (ABS). It can actually make your brakes and ABS less effective.
If you remove an inch from the tire’s profile for every inch you add to the wheel’s diameter, you can avoid the above two problems and improve feel through the steering wheel.
However, your rims will be closer to bumps and potholes, meaning your rides will be a little more painful.
Speedometers typically measure speed by the rotation of your wheel. If you change the size of your wheel and don’t compensate for the difference in diameter in your tire’s profile, your speedometer will be inaccurate.

Changing the size of your wheels can affect how other components in your car operate. Be sure you have a grasp of the big picture before you buy.

Upgrading to Wider Wheels

What if the new wheels you want are wider rather than larger? What considerations do you have to keep in mind then? We’re glad you asked.

You can add maybe an inch in width on a car’s wheels before you risk rubbing against other components.
Wider wheels can improve grip on the road.
Increasing wheel—and therefore tire—width can also increase hydroplaning on wet roads.
Wider tires have more rolling resistance, which will affect your fuel economy.

Although increasing the width of your wheels increases the contact patch—how much tire meets the road—it doesn’t improve grip in all situations. Moreover, it can cost you more money in fuel over the lifetime of your wheels.

Other Considerations You Need to Make

Heavier wheels, whether larger, wider, or both can affect ABS brakes, acceleration, speedometer, and fuel economy. They may also require special adjustments during installation. Ideally, stay within wheels made for your make and model, though they don’t need to have been made by your manufacturer.

But before you select your wheels, you need information about the wheels you have. That starts with finding your tire size and your rim size.

How to Find Your Tire Size and Rim Size

Before you upgrade anything, you need to gather information from your current tires to get a starting point. Look at the side wall of a tire, and you’ll find numbers that look like this: P235/65 R 17 104H. Here’s how they break down:

The P is for a passenger tire. Tires for a light truck will have the letters LT.
Next comes the width of the tire at its widest in millimetres. Our example above says 235 mm.
After the slash is the tire’s aspect ratio, only two digits. This is the height of the sidewall as a percentage of the tire’s width. In our example, the sidewall is 65% of the tire’s width.
The following letter refers to the tire’s construction. In our example, we’re dealing with a radial tire, which is what you’ll find on most passenger vehicles.
Rim size is the next number. It’s measured in inches. (Yes, inches, not millimetres.) Our example wheel has a rim size of 17”.
Load index follows and tells you the maximum weight a tire can handle when properly inflated. The number is not the actual weight, though: you have to reference a load index chart. This tire can carry up to 1,984 lbs.
The last letter is the speed rating. Tires with a speed rating of H can handle speeds of up to 200 kph. (But please obey speed limits.)

Pay Attention to the Details

No matter what wheels you upgrade to, they’ll still need to carry and manoeuvre your vehicle, and the numbers on the sidewalls of your current tires will give you a starting point. For example, you don’t want wheels and tires with a lower load index than your current set. You may also wish to stay with 17” rims to avoid many of the problems we listed above. Upgrading your wheels should be fun—there are so many designs and colours to choose from. But you want to enjoy your new purchase, too. Take the time to research your options properly, and when in doubt, ask your mechanic. Remember: your wheels don’t only carry you from Point A to Point B. They’re also one of the most important safety features on your vehicle. You don’t want to mess with them, even when you want to give them a funky upgrade.