How do you measure a car rim or wheel?

The wheels that come with your car are designed to work perfectly with its suspension, gearing, and body—everything that affects how it drives and performs. But hey, that doesn’t mean you’re stuck with them! You can definitely switch things up with a different wheel size or new rims. The trick is knowing what fits and what doesn’t. So, how do you figure out the right size for your car’s rims/wheels? Let’s find out.

How to measure your rims

When it comes to checking if a rim will fit, there are five key measurements you need to know: diameter, width, bolt pattern, offset, and backspacing. These numbers are essential for making sure the rim works with your vehicle and tires.

Here’s the trick: you need to know when to include or ignore the rim’s lips in your measurements. For width and diameter, always ignore the lips. But you’ll need to include offset and backspacing. Getting these measurements right is the key to finding the perfect fit for your tires. To get accurate numbers, always remove the tire and take the rim off the wheel before measuring. Here’s how to measure the rims on your vehicle:

Wheel diameter

To properly measure the diameter of your wheel, start by laying the rim flat on a stable surface and grabbing a tape measure—ideally one with a metal hook, which makes things easier. Hook the measuring tape onto the outside edge of the rim's lip and stretch it straight across to the opposite side.

Now, here's the key: you’ll need to subtract the width of the lip twice (once for each side) to get the true diameter of the rim. This gives you the actual size without the extra bulk of the lips.

If you want, you can measure from the inside edge of one lip to the opposite side instead, but it can be a bit tricky since the tape won’t lie perfectly flat. Stick with the first method for the most accurate results. Wheel width is usually measured in inches.

Rim width

The width of a rim is important because it determines what size tires you can use without messing with your vehicle’s performance. So, getting an accurate measurement is key.

Here’s how you do it: Stand the wheel upright, resting on its edges or lips. Hold your measuring tape on the inside of one lip, then stretch it across to the inside of the opposite lip. That distance—inside lip to inside lip—is your rim’s width. Wheel width is measured in inches and usually goes up in ½-inch increments.

Bolt patterns

Even if a tire fits the rim and the size is perfect for your vehicle, the rim won’t work if the bolt pattern doesn’t match. The bolt pattern refers to the number of studs that hold the lug nuts in place, so it’s crucial to get this right.

To measure the bolt pattern, lay the rim flat with the bolts facing up. First, count the bolts to see if it’s a 4, 5, 6, or 8-lug pattern. Then grab your measuring tape:

• For 4, 6, or 8-lug patterns, measure across the rim from the center of one bolt to the center of the bolt directly opposite.
• For a 5-lug pattern, measure from the center of one bolt to the outer edge of a bolt on the opposite side.

Bolt pattern measurements are usually taken in millimetres.

Offset and backspacing

Wheel offset and backspacing measurements are key when figuring out if your rims will fit properly and clear the brakes:

• Offset is the distance from the back of the mounting face (where the rim attaches to the car) to the centerline of the wheel.
• Backspacing measures how much space is behind the mounting face.

The mounting face is the backside of the rim’s center section, where the bolt pattern connects to the brake disc. Here's how offset works:

• Zero offset means the mounting face is exactly in the middle of the rim.
• Negative offset happens when the mounting face sits behind the centerline, pushing the wheel outward. This is common on older or more exotic vehicles.
• Positive offset means the mounting face is in front of the centerline, pulling the wheel inward. This is the most common setup since it leaves more room for the brakes and improves stability.

To find the offset, start by measuring the total width of the wheel from the outer lip on one side to the outer lip on the other. Then, divide that width in half. This gives you the centerline of the rim. Next, flip the rim so the inside faces up. Hook your measuring tape against the back of the mounting face (where the bolts are) and stretch it straight up to the outer edge of the rim. Finally, subtract the centerline measurement from the backspacing—that’s your offset. Offset measurements are usually taken in millimetres.

How to read the information on your tire

You’ll find important tire information on the sidewall of your tire or sometimes on a sticker inside the driver’s door. Those numbers and letters might look like a secret code, but they actually tell you a lot: the size, tire type, width, aspect ratio, construction type, wheel diameter, load index, and speed rating. Here’s a quick breakdown:

Metric sizing

The first letter indicates the tire class:

• P is for passenger vehicles
• LT is for light trucks
• ST is for special trailers

Width

The first number in your tire size tells you the tire’s width, measured in millimetres. This is the distance from one sidewall to the other. For example, if your tire size starts with “P225,” it means it’s a passenger vehicle tire (P) with a width of 225 millimetres.

Aspect ratio

The number right after the slash in your tire size is the aspect ratio, which tells you how tall the tire’s sidewall is. It’s given as a percentage of the tire’s width. For example, if a tire has an aspect ratio of 70, that means the height of the sidewall is 70% of the tire’s width.

Construction

The construction type is shown by another letter:

• R means radial tires
• D stands for diagonal plies (also called bias tires)

Rim diameter

The next number tells you the rim diameter, in inches, that the tire is designed to fit.

Load index

The number that comes after the rim size is the tire’s load index. This shows how much weight the tire can safely support when it’s fully inflated.

Learn more with BrokerLink

Having the right wheels on your car is crucial—but so is having the right car insurance. If you’d like to learn more about how the right coverage can protect your vehicle, reach out to BrokerLink! Our licensed insurance advisors are here to answer any questions you have about car insurance, such as whether you need collision coverage or how to file a claim.

You can connect with us by phone, email, or in person at one of our locations across Canada. Prefer to keep it online? Try our free online quote tool—it’s quick and gives you a competitive quote in just minutes. No matter how you choose to reach out, we’re here to help!

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FAQs about car rims and wheels

Where is the rim size stamped?

The rim width is part of the wheel size, and you can usually find it stamped on the backside of the wheel, on the back of a spoke or engraved into the barrel. Since these codes are often stamped inside the wheel, you may need to safely remove the entire wheel and tire assembly to read it.

How to measure a rim size?

With the tire removed, stand the wheel upright, resting on its edges or lips. Take your measuring tape, place it on the inside of one lip, and stretch it straight across to the inside of the opposite lip. That measurement is your rim’s width. Make sure you're measuring it from the inside of the lip and not the outside. Rim size is typically measured in inches.

Did a pothole damage my wheel rims?

Yes, it’s definitely possible. Hitting a pothole can bend or even crack your wheel rims, which can mess with both the look and performance of your wheels. Damaged rims might cause your tires to lose pressure and make your ride feel uneven.

Does insurance cover hitting a curb?

Ultimately, whether your car insurance covers hitting a curb depends on the coverage in your policy. Collision coverage is a type of car insurance that helps cover damage to your car, even if the accident is your fault. It can pay for repairs if you hit another vehicle or if you're in a single-vehicle accident, like hitting an animal, a median, a lamp post, or even a curb. If your policy includes collision coverage, there’s a good chance you’re covered!

How long does scheduled car maintenance take?

The length of a vehicle maintenance appointment can vary depending on the auto shop, your car’s make and model, and the specific services being done. Generally, though, you can expect it to take anywhere from one to five hours. For basic services like topping up fluids, checking tire pressure, cleaning the interior, and an oil and filter inspection, it usually doesn’t take too long.

If you have any questions, contact one of our local branches.