Wheel Sizes Explained

Maybe you’ve decided it’s time to upgrade the look of your ride with new wheels, or considering another set of wheels and tires for specific purposes like off-roading or winter driving. If finding original equipment (OE) replacement tires is fairly straightforward, the introduction of wheels into the equation can make things quite a bit more complicated. Just about any vehicle can accommodate a larger or smaller wheel size than stock, and depending on your vehicle and purposes, the ideal wheel size and specification can vary significantly.

To get you briefed on the basics and headed in the right direction, let’s start with some commonly asked questions about wheel sizes and aftermarket wheels.

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What is wheel (rim) width?

Imagine a wheel separated from the vehicle and positioned upright as normal (ready to roll). As you look down at the wheel, the width is the measurement from left to right between the wheel edges, also called the wheel lips.

The width of the wheel, from left to right.

Wheel width is measured in inches, and typically in ½" increments.

Sometimes the four stock wheels and tires on a vehicle are the same width. This is called a “square” setup. A “staggered” setup is a case in which the wheel and tire widths at the front and rear axles are different. For more information see Staggered vs. square tire and wheel setups.

How wide or narrow should your new wheels be?

Wheel width on a new set of wheels should be primarily determined by two considerations: Clearance and purpose.

What do we mean by “clearance?”

Within each wheel well is spacing between the wheel and tire and the surrounding vehicle components. This amount of space varies from vehicle to vehicle. Certain trucks have the wheel well space to accommodate a much wider wheel than stock, whereas other vehicles are able to fit only a slightly wider wheel than stock (if at all) without modification in the wheel well area. The space between your stock wheels and tires, and all surrounding vehicle components is called clearance.

Regardless of whether your purpose in fitting new wheels is advanced by a wider set of wheels, you are first and foremost limited by the available clearance.

To determine clearance, an automotive professional will need to measure and evaluate the space between your stock wheels and tires and all surrounding components. Clearance should be evaluated at both the front and rear axles, and while the suspension is loaded with the vehicle weight. (Unloaded suspension changes the geometry, and could lead to inaccurate clearance measurements.) Be sure to also take clearance measurements in the front wheel wells while moving the steering wheel from lock to lock.

If you carry heavy loads or haul a trailer, and/or drive over rough roads, be sure to account for the added vehicle weight, a compressed suspension system, and an associated loss of clearance.

A safe clearance between the wheels and tires and all vehicle components in the wheel wells should always be maintained. If the wheel and tire setup is too wide, serious vehicle damage and compromised vehicle safety can result.

Clearance measurements and maximum wheel width recommendations are best handled by automotive professionals.

The other important consideration when deciding on wheel width is “purpose.”

If your purpose in fitting a new set of wheels is to enhance or change the look of your ride, then sticking with the OE wheel width(s) front and back is the best route. The stock wheel widths were established after considerable engineering and vehicle testing, and so if there’s no good performance reason to alter wheel width, well then, there’s just no good reason.

If specific performance is the goal, then it may be that going with a wider or narrower wheel than stock will help you better accomplish those goals.

For example, winter tire and wheel setups are conventionally narrower than stock wheels and tires. The narrower footprint allows the wheels and tires to better “slice” through wintry precipitation.

On the other hand, off-road performance is typically enhanced by a wider wheel and tire footprint. A wider setup allows for more tire contact patch, and more traction in various off-road conditions.

The same is true of high performance driving – the maximum grip level of performance cars can be enhanced with a wider wheel and tire setup. At Track Days and high performance driving events, wider wheels and tires are the norm.

And so a decision on wheel width comes down to clearance and purpose. Both variables have to be carefully considered.

How to tell if rims will fit my tires?

This is typically a question for drivers who are looking to upgrade the look of their wheels, but keep their stock tires and not alter vehicle performance.

As previously suggested, when pursuing a wheel upgrade for cosmetic purposes, the best (and safest) route is to maintain the stock wheel specifications – this means maintaining both wheel width and diameter.

If these wheel specifications are kept consistent, then your stock (OE) tires will fit the new rims equally well.

If you change rim width or diameter, e.g. moving from an 18" wheel to a 19" wheel diameter, then your stock tires will no longer fit the rims.

How do I tell wheel size?

If you’re looking to learn the diameter of your stock vehicle wheels – sometimes thought of as wheel height, or how tall the wheel is – the easiest method is to review your tire size information.

The final number in your tire size (before the separate load index and speed rating) denotes both tire and wheel size. In the diagram just below, the size is 17 which translates to 17". This tire is fitted to a 17" wheel.

Where to find your tire’s diameter

Determining wheel width is a bit trickier. The tire section width, which is the first number in the tire size sequence and expressed in millimeters (“225” in the diagram above), hints at the wheel width, but does not give a certain or conclusive answer. This is because any given wheel width can accommodate more than one tire width. A 225 millimeter section width tire, for example, can be fitted to an 8" or 8.5" wide wheel.

To determine wheel width and the full specification details of your stock wheels, the dealership service department is often a good resource. Then with the full stock wheel specification in hand you can look for equivalents or close matches.

What is wheel diameter?

Wheel diameter is perhaps most easily thought of as the measurement from top to bottom, or across the face of the wheel.

Tire size details are a clear indication of wheel diameter as detailed above.

If wheels are not fitted with tires, a standard measurement with a tape measure will tell you what you need to know. Exclude the outer wheel lips that hold the tire in place as a part of the diameter measurement. The diameter measurement occurs across the front face of the wheel, excluding the lips/edges.

The wheel diameter

What is the diameter of a wheel?

Wheel size has been both popularized and simplified in modern pop culture. In music or elsewhere you might have heard wheels referred to as “20s,” “22s,” “Dubs,”etc.

These are references to the diameter of the wheel. Because the diameter (face) of the wheel is most influential on the look and profile, that’s what gets the attention.

The wheel “face”

In reality, the diameter is just one of the important wheel specifications and measurements, along with wheel width, offset, and backspacing.

To get a proper wheel fitment for your vehicle you’ll definitely need to consider more than just wheel diameter, no matter how cool simply having “20s” may be.

What is wheel offset?

So far we’ve touched on exterior wheel measurements and clearance factors, but that’s only part of the equation. What occurs in the space inside of your wheel barrels once they’re mounted is equally important.

Wheel offset is a measurement from the rear (inside) the wheel mounting face to the center of the wheel. Wheel offset adjusts the wheel either inward or outward once mounted. Similar to the diameter and width, offset directly affects vehicle component clearance.

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The wheel “offset” (click for larger)

What is wheel backspacing?

Wheel backspacing is essentially an extension of the wheel offset measurement. Instead of to the centerline of the wheel, the backspacing measurement occurs from the rear of the mounting face to the back (inside edge) of the wheel lip.

Both wheel backspacing and offset influence the spacing to the components inside of the wheel well, especially the brake calipers, as well as various suspension components. Like clearance measurements for wheel diameter and width, confirming sufficient clearance to these vehicle components is vital to ensure proper vehicle performance and safety.

If in doubt, or don’t want to take any risk, selecting a wheel that is an OE equivalent in terms of diameter, width, offset, and backspacing measurements is safest.

How to make sure that rims will work with tires?

Width and diameter are the two factors that determine tire and rim compatibility. For diameter you’ll need to be sure that your tires and wheels are an exact match, e.g. a 215/65R17 tire will only fit on a 17" diameter wheel.

There’s a bit more flexibility when it comes to wheel widths. Here is a guide for appropriately matching up tire and wheel widths:

Matching tire width to wheel width depends on your purpose. For off-roading, the tire width is typically wider than the wheel. This creates more sidewall bulge to protect your wheel from rocks and keeps the tire from de-beading off the wheel when running low psi off-road. For example a tire size 35X12.50-20 is typically fitted on a 9.0" wide wheel, therefore the tire width is 12.5" with the wheel much narrower than the tread width. For sports cars, the general rule of thumb is to match the wheel width to the tread width in inches. For example a tire size 285/35-19 has a tread width of 9.9". The ideal wheel width would be 10.0" for that tire. The tread width can be found on the tire manufacturer’s websites under the specifications along with the minimum and maximum rim width range. 

What do bigger wheels do for a car?

You mean, other than enhance the cool factor?

Bigger aftermarket wheels are perhaps most often fitted to vehicles for cosmetic purposes. They can have a profound influence on the look and presence of a vehicle.

Bigger wheels and the accompanying bigger tires can have a favorable influence on certain vehicle performance purposes like off-roading.

For on-road purposes, fitting a larger wheel generally means decreasing the tire sidewall and increasing tire width. A decrease (shortening) of tire sidewall can improve vehicle responsiveness, handling, and feel, while expanding tire width can improve all-around grip under acceleration, braking, and cornering.

Looking to get started on a search for aftermarket wheels for your vehicle? Check out our collection of wheels.

Get the right tires for your car or truck.

Tell us what you drive and we’ll show you all the best options.

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