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Old 10-23-2011, 10:08 PM   #1
ssmike
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Can someone please explain offsets?

OK, can someone explain what offsets are and what the proper offsets would be for any given wheel tire combo? There are so many wheels and tire combos out there, how do I know what the proper offsets are in order to get proper centering of the wheels in the fender wells?
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Old 10-23-2011, 10:54 PM   #2
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Originally Posted by ssmike View Post
OK, can someone explain what offsets are and what the proper offsets would be for any given wheel tire combo? There are so many wheels and tire combos out there, how do I know what the proper offsets are in order to get proper centering of the wheels in the fender wells?
The offset is the distance between the center on the wheel and the mounting pad of the wheel. The higher the offset the more a wheel will push in, the lower the offset the more it will push put.

A proper offset for a camaro will vary on the width of the wheel but it does need to be high such as +30 to +40 on the rear and can be a little lower such as +20 on the front.

You cannot always pick a wheel based on the offset alone, especially on a Camaro SS. Because of the larger brembo calipers you also need to consider the lip size and the actual design of the wheel.
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Old 10-24-2011, 12:54 AM   #3
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piece of cake......

I have seen this question ask many times recently, WHAT IS OFFSET? or BACKSPACING? or the terms used incorrectly, for they are not the same thing....SO with that in mind, here is an explanation of these two terms.

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Wheel Offset

Offset is measured from the centerline of the barrel of the wheel to the hub mounting surface. If that hub mounting surface were in the exact center of the barrel of the wheel the offset would be “0". If the mounting surface is away from the center of the wheel the offset is POSITIVE, if the mounting surface is towards the center, the offset is NEGITIVE. Offset is measured in millimeters. There are 25.4 millimeters to an inch. So if the mounting surface is 12mm from the centerline of the wheel it has a 12mm offset. That would also mean that it is about ½ inch. If the mounting surface is moved away from the vehicle that is a positive offset. The picture shows a wheel with the positive offset. A positive offset will cause the wheel to set in or tuck into the vehicle. Originally you found positive offsets on just front wheel vehicles. Due to that some people refer to positive offset wheels as front wheel drive offsets. Currently there are many rear wheel drive cars and trucks with positive offsets. The higher the positive offset the less it sticks out from the vehicle and it will have a higher Backspace. If the mounting surface is moved in toward the vehicle past the centerline, that is a negative offset. A high negative offset will produce a lower Backspace. Once again the measurement in millimeters is how far away from the centerline the mounting surface is. A -24mm offset means that the mounting surface is located 24mm or 1 inch from the centerline toward the vehicle. The wheel will come out farther from the vehicle and will have that deep dish look.

Width

The width of a wheel is measured inside the beads which are usually ½ inches. If you measure on the outside of the beads an 8 inch wheel will measure 9 inches

Backspace

Back spacing is measured from the inner edge of the wheel to the hub mounting surface. It is a convenient measurement in that, as long as the back spacing remains the same, the clearance to the suspension also remains the same. If you know the width of the wheel and the offset you can compute the backspacing. For example if you have an 8 inch wheel with a +24mm offset. An 8 inch wheel is actually 9 inches wide so if the offset were 0 the mounting surface would be right on the centerline and the backspacing would be 4.5 inches. With a positive offset the mounting surface moves off center 24mm or 1 inch toward the outer edge of the wheel. This will make the inner edge go more inside which will result in a 5.5 inch backspacing.

Centerbore

This is the diameter of the center of the wheel. The centerbore must be equal to or larger than the hub of the vehicle for the wheel to seat. If the wheels centerbore is the same as the hub on the wheel then that wheel is hub-centric and uses the hub to center the wheels. If the centerbore is larger than the hub then the lugs will center the wheel and that is lug-centric. When using a lug-centric wheel be sure and snug the lugs up slowly and tighten them in an opposite or star pattern.

Bolt pattern

A bolt pattern of 5x120 mm means it has 5 lugs and if there were a circle through the center of all the lugs the diameter of that circle would be 120 mm.
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Old 10-24-2011, 06:19 AM   #4
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Quote:
Originally Posted by Sir Nuke View Post
piece of cake......

I have seen this question ask many times recently, WHAT IS OFFSET? or BACKSPACING? or the terms used incorrectly, for they are not the same thing....SO with that in mind, here is an explanation of these two terms.

Attachment 299744

Attachment 299745


Wheel Offset

Offset is measured from the centerline of the barrel of the wheel to the hub mounting surface. If that hub mounting surface were in the exact center of the barrel of the wheel the offset would be “0". If the mounting surface is away from the center of the wheel the offset is POSITIVE, if the mounting surface is towards the center, the offset is NEGITIVE. Offset is measured in millimeters. There are 25.4 millimeters to an inch. So if the mounting surface is 12mm from the centerline of the wheel it has a 12mm offset. That would also mean that it is about ½ inch. If the mounting surface is moved away from the vehicle that is a positive offset. The picture shows a wheel with the positive offset. A positive offset will cause the wheel to set in or tuck into the vehicle. Originally you found positive offsets on just front wheel vehicles. Due to that some people refer to positive offset wheels as front wheel drive offsets. Currently there are many rear wheel drive cars and trucks with positive offsets. The higher the positive offset the less it sticks out from the vehicle and it will have a higher Backspace. If the mounting surface is moved in toward the vehicle past the centerline, that is a negative offset. A high negative offset will produce a lower Backspace. Once again the measurement in millimeters is how far away from the centerline the mounting surface is. A -24mm offset means that the mounting surface is located 24mm or 1 inch from the centerline toward the vehicle. The wheel will come out farther from the vehicle and will have that deep dish look.

Width

The width of a wheel is measured inside the beads which are usually ½ inches. If you measure on the outside of the beads an 8 inch wheel will measure 9 inches

Backspace

Back spacing is measured from the inner edge of the wheel to the hub mounting surface. It is a convenient measurement in that, as long as the back spacing remains the same, the clearance to the suspension also remains the same. If you know the width of the wheel and the offset you can compute the backspacing. For example if you have an 8 inch wheel with a +24mm offset. An 8 inch wheel is actually 9 inches wide so if the offset were 0 the mounting surface would be right on the centerline and the backspacing would be 4.5 inches. With a positive offset the mounting surface moves off center 24mm or 1 inch toward the outer edge of the wheel. This will make the inner edge go more inside which will result in a 5.5 inch backspacing.

Centerbore

This is the diameter of the center of the wheel. The centerbore must be equal to or larger than the hub of the vehicle for the wheel to seat. If the wheels centerbore is the same as the hub on the wheel then that wheel is hub-centric and uses the hub to center the wheels. If the centerbore is larger than the hub then the lugs will center the wheel and that is lug-centric. When using a lug-centric wheel be sure and snug the lugs up slowly and tighten them in an opposite or star pattern.

Bolt pattern

A bolt pattern of 5x120 mm means it has 5 lugs and if there were a circle through the center of all the lugs the diameter of that circle would be 120 mm.
Best explanation of wheel offsets, backspacing, and center bore that I've ever seen.

mods, you should sticky this one!

*edit, never mind, I just saw the link in the sticky section.
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Old 10-24-2011, 07:41 AM   #5
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Originally Posted by monstertodd View Post
Best explanation of wheel offsets, backspacing, and center bore that I've ever seen.

mods, you should sticky this one!

*edit, never mind, I just saw the link in the sticky section.
Thanks...........at the top there is a sticky that is titled
WHEEL/TIRE INFORMATION RESOURCES" its in there......in order to clean up some things a while back, there was one link or jump spot put together for a number of threads.
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Old 10-24-2011, 08:40 AM   #6
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Great info guys! Didn't see that in the sticky! Thanks!
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