ATV Wheels: A Guide for Determining the Correct Size
By Midwest Traction on September 9, 2017
Tips & Advice
Wheel Terminology (More Below)
Offset: The distance between the mounting surface to the true centerline of the rim. (Backspacing, which is similar to offset, is the distance from the hub mounting surface to the inside lip of the ATV wheel, measured in inches).
Centerline (Zero Offset): The exact center of the rim width. The total width is measured between where the ATV tires rest, inside bead rest to inside bead rest. (Example below is for an 8 wheel with a 4+4 offset)
Negative Offset: The mounting pad sits behind (or inboard of) the centerline of the rim. With this type of mount, the tire will stick out, away from the vehicle. It is often found on standard rear-wheel-drive ATV vehicles and on reversed or deep-dished rims. (Example below is for an 8 wheel with a 3+5 offset)
Positive Offset: This is when the mounting pad is positioned in front (or outboard) of the centerline of the rim. ATV tire fits further into the fender well. Most often located on the front wheels of 2WD, and all front and rear wheels of independent 4WD ATV applications. (Example below is for an 7 wheel with a 5+2 offset)
How To Measure Wheel Bolt Pattern
3-LUG: Measured by the diameter of an imaginary circle (bolt circle) that goes through the center of all three bolt holes (diagram A, below, shows a 3/90 bolt pattern, where measurement A is 90mm).
4-LUG: Measured by the distance between opposite or diagonal holes (see diagram B, below, of a 4/110 bolt pattern where measurement B is 110mm).
5-LUG: For a five-lug application there are a couple of methods to choose from. For the most common patterns used in the trailer and automotive wheels, measure the center-to-center distance between two adjacent wheel studs and reference to these calculations: 2.645 in. = 4 ½ in. circle, 2.792 in. = 4 3/4 in. circle, 2.939 in. = 5 in. circle, and 3.233 in. = 5 ½ circle. For most ATV applications, you can measure from the back of one hole to the center of the corresponding diagonal hole (see diagram C, below, of a 5/110 bolt pattern, where measurement C is 110mm).
How To Read Wheel Sizing
When shopping for 5-LUG wheels, you will notice the listing looks something like this:
Wheel PCD: 4/110
But what do all the numbers mean?
Size: 8×8 The first number is the diameter of the wheel and also the inside diameter of the tire. The second number is the width of the wheel. Use an 8 wheel with an 8 tire.
Offset: 3+5 This is the offset of the wheel. The first number indicates the off-center inside, while the second number indicates the offset to the outside.
Wheel PCD: 4/110 The first number indicates the number of bolt holes in the ATV wheel. The second number indicates the spacing of the bolt holes (usually in millimeters). The Pitch Circle Diameter refers to the diameter of the circumference of the center line of the lug nut holes (bolt circle/bolt pattern). PCD is not used much these days, mainly by engineers, and has confused a lot of people think it is something else.
Bead Seat – The position where the ATV tire rests and seals on the inside of the rim.
Center Bore – The hole in the center of the wheel is machined to match the hub of specified vehicles with hub-centric wheels and machined to a generic size with lug-centric wheels.
Hub Centric – The center bore hole of a wheel matches the hub diameter of the vehicle. This centers the wheel via the center hole rather than the lug nuts.
Lug Centric – When the wheel is centered by the bolt holes/ lug nuts of the wheel, rather than by the center bore.
Mounting Pad – The surface area on the back of the wheel’s center that makes contact with the brake drum or rotor surface.
Backside Setting/Back Spacing – The measurement from the mounting pad to the inner edge of the wheel.
Rim Width – The width of the custom wheel, measured from bead seat to bead seat, rather than edge to edge.
Rim Diameter – The overall diameter of the wheel’s bead seat, not the diameter of the rim edge.
Rim Flange – The outermost edge of the wheel’s rim that the clip-on weights attach to on most wheels.
Safety Bead – The raised area circling the rim of the wheel, located slightly inward from the bead seat.