Why You Should Know Your Wheel Dimensions: Explained
So, aside from an increase in performance, why would you want to change your stock wheels in the first place? We're glad you asked. There are plenty of reasons to make a wheel upgrade. You might want an extra set of wheels and tires for easy installation when you swap out your current set for the winter months. Or, you might be going for a specific look that accentuates your personality – maybe you're thinking stylish and sleek for your sports car or rugged and relaxed for your brand new pickup.
Whatever your reasoning is, it's essential to get your wheel measurements correct, or your plans could backfire. If you end up with the wrong wheel setup, you could experience heavy vibrations when cruising down the open road. Or, you might feel some intense rubbing on your suspension components and vehicle body parts that could put your tires out of commission. No one looks cool jolting and bumping down the street – trust us.
How to Measure Rim Size and Bolt Pattern
Wheel measurements aren't too hard to understand – that is if you know what you're looking for. Knowing how to read rim size and understand your bolt pattern are two of the most crucial elements to finding a perfect fit.
Rim Size: Explained
When you want to purchase new wheels, the first thing you'll want to look at is your rim measurements. Knowing how to read your rim size is relatively easy. You can find the information on the sidewall of your tires or the inside of the frame of your driver's side door. Your rim size will be the fifth set of letters or numbers listed on this information. Rim size numbers represent the distance between the two bead seat areas where the tire is sealed onto the wheel.
As with all the wheel measurements in this guide, you'll want to write these down so you can easily input the information later.
Bolt Pattern: Explained
One of the more complex wheel measurements you'll need to find is the bolt pattern. Your bolt pattern is made up of two numbers found on the back of the hub on the rim and will indicate how many bolt holes your wheel has as well as the diameter of the imaginary circle these bolt holes create. For example, if your bolt pattern reads 4-100, your wheel measurements include four lug holes around a 100mm diameter circle. However, keep in mind that manufacturers can display the diameter in inches or millimeters.
You can also measure the bolt pattern yourself if you're having trouble locating the numbers. All you have to do is measure center to center of two bolt holes directly across from one another. Easy enough, right?
Some of the more common wheel bolt patterns you'll see when doing your wheel measurements include four-lug, five-lug, six-lug and eight-lug patterns.
How to Measure Wheel Diameter
Your wheel diameter is the distance measured across the face of the wheel from bead seat to bead seat. Wheel diameter is typically measured in inches. You measure wheel diameter in this fashion because the area between the two bead seats is where the tire and the wheel come together. Wheel diameter varies from manufacturer to manufacturer, but it typically falls in a range of 13 inches to 24 inches. Higher measurements are generally reserved for specialized low-profile fitments.
Pro Tip: You can usually find your wheel diameter stamped between one of the spokes on the backside of the wheel.
How to Measure Wheel Width
When it comes to learning how to measure wheel size, your wheel width measurements are very similar to measuring your wheel diameter. Wheel width is the distance, once again in inches, across the wheel's barrel. Make sure that when you measure wheel width, you are only taking the barrel width into account, rather than measuring from rim flange to rim flange. The most common wheel width measurements you'll find are from 6 inches to 14 inches.
Please Note: When browsing for a new set of wheels, keep in mind that decreasing or increasing your wheel width can directly impact your tire's contact patch. This will affect how your ride handles, so you don't want to go too overboard.
How to Measure Offset
Your wheel offset is the distance from the hub mounting surface to the centerline of your wheel. This is an essential wheel measurement to look out for when choosing your next set of car or truck wheels. There are three different types of offsets, all of which you can measure in millimeters:
- Positive Offset: When your hub mounting surface is toward the face of your wheel
- Negative Offset: When your hub mounting surface is towards the back of the wheel
- Zero Offset: When your hub mounting surface is positioned evenly with the centerline of the wheel
Most wheels will have the offset number embossed on the wheel's back on the mounting plate or the back of one of the spokes. When performing your wheel measurements, you may see something that reads +40mm. This means the mounting surface is positive and is 40mm away from the wheel's centerline.
Getting your offset correct in your wheel measurements is essential for a few reasons. The right offset can prevent your wheels and tires from rubbing the fenders, brakes and suspension components. Offset also determines your wheel stance and changes whether they sit tucked under the fenders or push out past them.
How to Measure Backspacing
Our final tip for how to measure wheel size involves backspacing. Backspacing is the distance from where your hub section contacts the hub surface to the back lip of the wheel. To measure backspacing, you can run a straight edge ruler across the rim bead (with the tire removed) and drop another straight edge or tape measure down your wheel face to measure the distance.
When it comes to wheel measurement, backspacing is always measured in inches and is closely related to the offset. When you change either backspacing or offset, it will immediately affect the other.
Getting your backspacing right is incredibly important in wheel measurement. It determines the clearance of the wheel-well and affects how much the wheel sticks out past the fender.