How to Measure UTV Wheels Offset
UTV wheel offset refers to the distance between the centerline of a vehicle’s front axle and the centerline of its rear axle. Offset is measured in inches, with zero being equal to no offset. The greater the number, the further back the wheels are positioned. The offset can affect axle durability, tire life, vehicle clearance to obstacles, and vehicle stability. When installing new wheels on a UTV, you need to ensure that they are either an exact match or have appropriate offset to fit the UTV.
Moreover, changes in offset with wear will affect the stability of the UTV and should be monitored as part of a regular wheel maintenance program. Size matters when it comes to wheels and tires. If you choose a wheel or tire that is smaller than what came stock, you'll need to move the axle forward to maintain proper handling. If a bigger wheel is used, you may also need to move the axle forward. This will also have an effect on the speedometer and odometer.
Different Styles of Offset
The difference in offset between a stock rim and different aftermarket rims can be substantial. The UTV owner’s manual will provide the specific measurements on what is acceptable, but generally speaking, if you want to use an aftermarket rim on your UTV, you must make sure it has either the same or a better offset than the original OEM rim. There are three different types of offset: positive offset, negative offset, and zero offset.
Positive offset wheels are positioned further forward than the vehicle’s centerline by about 3⁄4" on a standard 2WD UTV. A positive offset is generally reserved for trucks with axles in the rear of the vehicle. Positive offset wheels are typically more desirable because they allow room for longer suspension travel while improving weight bias to improve handling.
Negative offset wheels are positioned further back than the vehicle’s centerline by about 3⁄4" on a standard 2WD UTV. Negative offset is generally reserved for trucks with axles in front of the vehicle. Negative offset wheels are typically better suited to vehicles with a limited suspension stroke, as it will create more ground clearance and improve weight bias slightly.
Zero offset wheels are, as you’ve probably guessed, zero offset, meaning there is no fixed lateral position for the wheel. Zero offset wheels are acceptable for off-road vehicles with a limited suspension stroke such as mini utility vehicles. Zero offset wheels improve steering precision and handling but raise handling problems such as roll-over potential, lack of ride height adjustability, and instability.
How to Measure Wheel Offset
Wheel offset is typically determined by measuring the distance from the centerline of a vehicle’s front axle to the centerline of its rear axle. It can be measured using one of four methods: left and right tire (LT) LT+R and RT offsets, and LT+RT offsets.
- LT Offsets: On LT offsets, the measurement is taken from the outer edge of the left side tire to the outside edge of the right side tire.
- LT+R Offset: On LT+R offsets, the measurement is taken from the outer edge of the left side tire to the inside edge of the right side tire.
- LT+RT Offset: On LT+RT offsets, the measurement is taken from the inside edge of the left side tire to the outer edge of the right side tire.
- LT+R+RT Offset = LT Offset + LT+R Offset: The larger the difference between your wheel's LT offset and your UTV's rear axle's LT offset, the more stable your vehicle will be when off-roading. Overall, zero tire offsets are desirable on all off-road vehicles.
- LT+R+RT Offsets: This method is similar to LT+R offsets, but it adds another measurement to determine a precise reading. On LT+R+RT offset measurements, you measure from each outside edge of both tires to both inside edges of both tires. The measurement taken from the outside edge of the right side tire to the inside edge of the right side tire is called "LT+R offset." The measurement taken from the outside edge of the left side tire to the inside edge of the left side tire is called "LT+RT offset."
The tools you need to measure these angles are a tape measurer and a straight edge. The different methods that you can use to measure a wheel offset, such as:
1. Stud Method
The stud method refers to measuring the distance between a point on the rim lip to the center of a mounting hole. The most accurate stud method is accomplished by measuring from the top edge of the rim lip to a 90-degree angle machined point on the rim, then measuring from that point to the screw hole. The distance you’re measuring is the tire’s LT offset.
Positive offset wheels are typically expressed without decimals, while negative offset wheels have decimals. The upper right tire is designated “R”, while the lower left tire is designated “L”. For example, a tie rod measurement of 94mm + R and 82mm + L would correspond to an LT+R = 6mm and an LT+L = 4mm; a common positive offset.
2. Center Truss Method
The center truss method refers to measuring the distance between two machined points along the rim. The first point is located at 180 degrees from the rim’s center hole and is machined to a 90-degree angle. The second point is at 90 degrees from the hole and is machined to a 45-degree angle. Measuring from these two points, the distance between them corresponds to your wheel’s LT+R offset.
3. Center of Load Method
The center of load method refers to measuring the distance from the rim’s centerline to the centerline of your vehicle. Using an instrument called a "bulls-eye level," you can measure two points on your vehicle with a standard laser level and find the point on your rim that coincides with the bull’s eye. You can find your wheel's LT+R offset from that point and the 90-degree angle machined into the rim, you can find your wheel’s LT+R offset.
Measuring Tire Offsets
In order to get the LT offset of your wheel, measure the distance from the centerline of your wheel to the center line of your UTV’s rear axle. This measurement is called LT offset or "LT offset."
Measuring Axle Offsets
In order to get the LT+R offset, measure the distance from your wheel's centerline to the centerline of your UTV's rear axle. This measurement is called LT+R offset or "LT+R offset." The "LT+R offset" of your wheel corresponds to the LT offset of your UTV's rear axle.
Changing offset on a wheel is not an easy task and is best left to a professional mechanic. Adding or removing spacers may affect the stability of the vehicle and can even lengthen your stopping distance. Wheel manufacturers do not recommend changing offset on wheels in order to improve off-road performance.
Adding Positive Offset
Adding positive offset will make your vehicle less stable at high speeds and is typically done for aesthetic purposes. Adding positive offset can also affect the handling of your vehicle and make it more likely to roll over.
Removing Positive Offset
Removing positive offset increases stability at high speeds and makes it easier to regain traction while driving on rough terrain. Removing positive offset can also shorten your UTV's stopping distance.
Wheel backspacing is determined by measuring the distance from the center of a wheel's mounting surface to the outside edge of its rim. This measurement can differ from one vehicle model to another, as manufacturers often set their cars and tires to different specifications. A larger backspacing requires larger wheels and tires to mount them, while smaller backspacing results in a more aggressive appearance due to the wheels protruding out past the fenders.
Backspacing is measured by using a straight edge or tape measurer and measuring from the center of the wheel's mounting surface to its outside edge. Backspacing is typically expressed without decimals. The upper right tire is designated "R," while the lower left tire is designated "L.”
What Does Backspacing Have to Do with Wheel Fitment?
Wheel backspacing determines how wide or narrow a wheel looks when mounted on your UTV. Typically, a wheel’s measurements are associated with the width of the wheel. However, this is not always true. Wheel specs are based on "backspacing." For example, a wheel size of 17" × 7" will generally look narrower than a wheel size of 18" × 8". This is because the 17" × 7" wheel has a measurement of 5.5" backspacing, while the 18" × 8" wheel has a measurement of 6.35" backspacing.
When Is Offset a Problem?
The offset can be a problem for two different reasons. One, your vehicle's suspension geometry may not be compatible with a certain offset or two, some offset combinations require larger rim sizes to work. When it comes to suspension geometry, you'll typically find that the lowest offset on your vehicle will give you the best steering and performance. However, some taller suspensions will call for a higher positive offset because of the length of the arm needed to get back down to the lower negative offsets.
Which Offset Should I Use?
Since each rig and driver is different, there is no easy answer to this question. The offset can dramatically affect the handling of your vehicle and whether or not it will rollover. As a guideline, we recommend starting with the highest positive offset that will work with your suspension geometry. If you really want to eliminate any rollovers, you may want to try the lowest negative offset possible.