What does the offset mean?

ChevyHDGert · April 12, 2005

I'm looking at rims for my HD that have a 4.25" backspacing with a +18mm offset on the 16x8's and a -6mm offset on the 17x9's.

What is the difference?

snoman · April 12, 2005

I'm looking at rims for my HD that have a 4.25" backspacing with a +18mm offset on the 16x8's and a -6mm offset on the 17x9's.

What is the difference?

<{POST_SNAPBACK}>

The -6mm means the center line of rim is 6mm inboard on hub mount and the plus 18mm means the centerline is 18 mm outboard of hub face pushing the wheel further out and increasing the loading on the the wheel beaings and suspension a bit more too.

ChevyHDGert · April 12, 2005

Then you would think that they would have the offsets flipped on these two sizes.

Since the 17x9 is wider, you would think they would give it the positive offset so it tucks in more and give the 16x8 the negative offset. :think:

I was hoping to fit the 17x9's with 305/70/17 MT's without having to move my bumper out. Sounds like it is going to be way too wide to even attempt.

Maybe I better stick to 16x8's with 305/70/16 MT's.

As long as I get about 1" sticking out past the fender flare for that "bulldog" stance.

snoman · April 12, 2005

Then you would think that they would have the offsets flipped on these two sizes.

Since the 17x9 is wider, you would think they would give it the positive offset so it tucks in more and give the 16x8 the negative offset. :think:

I was hoping to fit the 17x9's with 305/70/17 MT's without having to move my bumper out. Sounds like it is going to be way too wide to even attempt.

Maybe I better stick to 16x8's with 305/70/16 MT's.

As long as I get about 1" sticking out past the fender flare for that "bulldog" stance.

<{POST_SNAPBACK}>

With wider tires and rims they have to "kick" them out so that you have turning clearance up front because with a wider rim and tire, even with offset the back of tire is close to original distance from frame and a increased offset is needed to do that.

Jacqson · April 13, 2005

I'm looking at rims for my HD that have a 4.25" backspacing with a +18mm offset on the 16x8's and a -6mm offset on the 17x9's.

What is the difference?

<{POST_SNAPBACK}>

The -6mm means the center line of rim is 6mm inboard on hub mount and the plus 18mm means the centerline is 18 mm outboard of hub face pushing the wheel further out and increasing the loading on the the wheel beaings and suspension a bit more too.

<{POST_SNAPBACK}>

snoman,you got that backwards. Offset is defined as "The distance from the rim centerline to the mounting face of the wheel". If you have a wheel with positive offset that means the wheel will be inboard not outboard. A +18mm offset will have the wheel centerline 18mm inboard of the mounting face of the wheel. Negative offset wheels stick outboard, Positive offset wheels go inboard. Negative offset has less BS, Positive offset has more BS. It can be really confusing.

snoman · April 13, 2005

I'm looking at rims for my HD that have a 4.25" backspacing with a +18mm offset on the 16x8's and a -6mm offset on the 17x9's.

What is the difference?

<{POST_SNAPBACK}>

The -6mm means the center line of rim is 6mm inboard on hub mount and the plus 18mm means the centerline is 18 mm outboard of hub face pushing the wheel further out and increasing the loading on the the wheel beaings and suspension a bit more too.

<{POST_SNAPBACK}>

snoman,you got that backwards. Offset is defined as "The distance from the rim centerline to the mounting face of the wheel". If you have a wheel with positive offset that means the wheel will be inboard not outboard. A +18mm offset will have the wheel centerline 18mm inboard of the mounting face of the wheel. Negative offset wheels stick outboard, Positive offset wheels go inboard. Negative offset has less BS, Positive offset has more BS. It can be really confusing.

<{POST_SNAPBACK}>

That is confussing if that is correct.

Mule · April 13, 2005

OK, guys, here is pictures:

http://www.usacomp.com/terms.htm

snoman · April 13, 2005

OK, guys, here is pictures:

http://www.usacomp.com/terms.htm

<{POST_SNAPBACK}>

Nice link!

gmc42 · April 15, 2005

I'm looking at rims for my HD that have a 4.25" backspacing with a +18mm offset on the 16x8's and a -6mm offset on the 17x9's.

What is the difference?

<{POST_SNAPBACK}>

The -6mm means the center line of rim is 6mm inboard on hub mount and the plus 18mm means the centerline is 18 mm outboard of hub face pushing the wheel further out and increasing the loading on the the wheel beaings and suspension a bit more too.

<{POST_SNAPBACK}>

snoman,you got that backwards. Offset is defined as "The distance from the rim centerline to the mounting face of the wheel". If you have a wheel with positive offset that means the wheel will be inboard not outboard. A +18mm offset will have the wheel centerline 18mm inboard of the mounting face of the wheel. Negative offset wheels stick outboard, Positive offset wheels go inboard. Negative offset has less BS, Positive offset has more BS. It can be really confusing.

<{POST_SNAPBACK}>

That is confussing if that is correct.

<{POST_SNAPBACK}>

Confusing but correct a positive offset wheel will move the tire/wheel inward, while a negative offset will move it outward giving you that bulldog look that you want. Check out other wheel sizes like a 10 or 12" They have negative offsets because they are too wide to fit otherwise. Stock newer gm trucks have a positive offset due mostly to their front end design, but negative offset wheels work fine in most cases. If you have larger than stock tires you may have fender clearance problems. I am running 35" tires on 10" wide rims with 3 3/4" backspacing (negative) with an 8" lift and have had no problems with bearings or anything else.

snoman · April 16, 2005

I am running 35" tires on 10" wide rims with 3 3/4" backspacing (negative) with an 8" lift and have had no problems with bearings or anything else.

<{POST_SNAPBACK}>

You will with time the only question is when because you are inducing a lot more stress of front end than it was designed for. Outset like that overstress the bearings and the suspension and steering and anything that is overstressed does have a shorter life but it jsut remains to be seen how much shorter amd what will fail first.