Wheels & Tires:What is Wheel Offset

Besides just the bolt pattern, to use a wheel from a different vehicle on your vehicle requires it to be measured for offset/backspacing to be sure the wheel will clear the suspension components. Changing the offset, even if it clears everything, can change the steering geometry, so make changes with this in mind.

WHEEL OFFSET

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Besides offset, there are other things that come into play, like the center bore of the wheel and the brake component clearance.

Backspacing
This is the distance from the inside edge (edge closest to the vehicle if mounted) of the wheel to the wheel's mounting surface.
In other words it is the measurement given from the back of the wheel to the hub mounting point.
Find your width and offset and get your backspacing. Hence, if you have an 8.5-inch-wide wheel and need 3.5 inches of backspacing, you would need a wheel with a -32 offset.

Center Bore
The center bore of a wheel is the size of the center hole in the wheel. This hole often is used to center the wheel on the hub or axle. This takes some of the load from the lugs/lug nuts as well. If the wheels center bore is less than the hub or axle center bore, the wheel will not fit despite the bolt pattern being correct. If the wheel center bore is larger, the wheel might not be as well supported as it should.

Brake Clearance
The inside diameter of the back side of the wheel must be able to accommodate the brakes, whether they are disc or drum.

What is offset?
Offset is the distance between the centerline of a wheel and the plane of the surface of the wheel that mounts to the vehicle. This will vary greatly depending on the application and whether the vehicle is front wheel drive or rear wheel drive.
"Deep dish" wheels are negative offset wheels. If taken to extremes this can cause undue stress on axles/spindles and bearings. Using an extreme amount of negative or positive offset is not a fix for an axle of the wrong width, despite the fact that the wheels fit under the fenders, etc.

The offset can be one of three types.

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Zero offset
The hub mounting surface is even with the centerline of the wheel.

Positive offset
The hub mounting surface is toward the front, or face, of the wheel.
Positive offset wheels are generally found on front-wheel-drive cars and newer rear-drive cars.

Negative offset
The hub mounting surface is toward the back, or brake side, of the wheel's centerline.
"Deep dish" wheels are generally a negative offset.

Figuring offset
Back spacing - Centerline = Offset
First, measure the overall width of the wheel at its widest point. Next, divide that width by two; this will give you the centerline of the wheel.
After determining the centerline, subtract the centerline from the backspacing to get the wheel offset.

Side note
If the offset of the wheel is not correct for the vehicle, the handling can be adversely affected.
If the width of a wheel changes, the offset of the wheel also changes numerically.
If the offset were to stay the same while you added width, the additional width would be split
evenly between the inside and the outside. For most vehicles, this won't work correctly.

List of truck correct offsets
This list will be for total millimeters of offset needed to achieve a low stance without modified fenders and bedsides.
This list contains no 4WD applications. Sorry!
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1983 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1984 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1985 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1986 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1987 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1988 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1989 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1990 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1991 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1992 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1993 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1994 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1995 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset
1996 Mitsubishi Pickup 6 lug 5.5 inch or 139.7mm Medium Offset

1988 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1989 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1990 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1991 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1992 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1993 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1994 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1995 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1996 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1997 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1998 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1999 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
2000 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
2001 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
2002 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
2003 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
2004 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
2005 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
2006 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
2007 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
2008 Mitsubishi Montero 6 lug 5.5 inch or 139.7mm Medium Offset
1997 Mitsubishi Montero Sport 6 lug 5.5 inch or 139.7mm Medium Offset
1998 Mitsubishi Montero Sport 6 lug 5.5 inch or 139.7mm Medium Offset
1999 Mitsubishi Montero Sport 6 lug 5.5 inch or 139.7mm Medium Offset
2000 Mitsubishi Montero Sport 6 lug 5.5 inch or 139.7mm Medium Offset
2001 Mitsubishi Montero Sport 6 lug 5.5 inch or 139.7mm Medium Offset
2002 Mitsubishi Montero Sport 6 lug 5.5 inch or 139.7mm Medium Offset
2003 Mitsubishi Montero Sport 6 lug 5.5 inch or 139.7mm Medium Offset
2004 Mitsubishi Montero Sport 6 lug 5.5 inch or 139.7mm Medium Offset
2005 Mitsubishi Montero Sport 6 lug 5.5 inch or 139.7mm Medium Offset

The expertise and judgment of the installer overrides any and all recommendations.
Created by , 03-14-2013 at 09:31 AM
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