12x7, 4+3, 4 on 156mm. No that's not a math problem. Those numbers are actually a common size for ATV wheels. Looking up new wheels can seem like an impossible undertaking, but once you know what each number stands for, you'll be able to pick out that new set of ATV rims in no time. Keep reading to have ATV wheel sizes explained.
As you can see in the above example, there are three sections in the wheel size, which are separated by commas. Each set of numbers denotes a different measurement of the wheel. To get the rim that you need, it's important to know what each set of numbers is and how to find the measurement yourself. In the order that they appear, the numbers represent rim size (diameter and width), wheel offset and bolt pattern.
ATV Wheel Size (Diameter and Width)
The first set of numbers that you will see in an ATV wheel size (12x7 from the example) is the diameter and width of the wheel. So with our example from above, the wheel will have a 12 inch diameter (height) and a 7 inch width across.
To measure for the diameter, stretch your tape across the widest part of the wheel from bead seat to bead seat.
For the width, you will need to measure across the wheel (outside to inside or vice versa) from bead seat to bead seat.
Note: For both measurements, be sure to measure from bead seat to bead seat, not from rim edge to rim edge. Rim edges or flanges can differ from brand to brand and even from style to style, which makes them an inconsistent measuring point.
ATV Wheel Offset
Moving on, measuring the offset entails a more involved process. If you've never been told how to measure the offset of an ATV wheel, chances are you'd be measuring your wheel for a while before you figured it out. To make it easier, you need to know what it is. Said plainly, the offset is the distance from the centerline of the wheel to the hub mounting surface.
So what's with the plus sign? Let's look at our example of a 4+3 offset. The "4" is the inside measurement in inches from the centerline of the wheel to the bead seat. This section is called the bell of the wheel. The "3" is the outside measurement from the centerline to the bead seat. This is the nose of the wheel and the side with the valve stem hole. When you put them together, the whole offset is then 4+3. When you add them together you should get the overall width of the wheel, which in this case is 7 inches (4+3=7).
There are three different types of offsets: positive, negative and zero offset.
Positive- A positive offset is when the bell section of the wheel is wider than the nose. Our example of the 4+3 would be a positive offset.
Negative- Just like you'd think, this is the opposite of a positive. The nose section of the wheel is the widest. An example would be a 3+4 wheel.
Zero- When the hub mounting surface is in the true center of the wheel, there is zero offset. A 4+4 would be an example of a zero offset ATV wheel.
It's important to pay close attention to the offset. A change in the wheel offset could affect your ATV's handling, smoothness of ride, spacing between the body and suspension and even the overall safety. To be safe, you should consult a technician to make sure that the change you make is safe for your machine.
Without switching out the hubs, you are limited to the one style of bolt pattern that your ATV already has. Your ATV will have one of three patterns: a 3-lug, 4-lug or a 5-lug pattern. The patterns do come in different sizes, though. Not all 3-lug patterns are the same and that also goes for the 4-lug and 5-lug patterns too. To find out which size you need, you will have to measure the pattern. With our example, 4 on 156mm, "4" is the number of bolt holes and "156mm" is the distance measured. To make things even a little more complicated, each lug pattern is measured differently.
3-Lug- Imagine a circle running through the center of each bolt hole. The diameter of that circle is the measurement.
4-Lug- To find the size of a 4-lug, simply measure the distance between the center of one bolt hole to the center of the hole directly across from it.
5-Lug- This one can be a little tricky. You need to measure the distance from the back of one bolt hole to the center of the hole that is two over from it.
That may be a lot to take in all at once, but once you measure a few times you will get the hang of it. To sum it up, let's break down our example.
12x7- The diameter x the width of the wheel
4+3- The offset of the wheel
4 on 156mm- The bot pattern of the wheel