I'm kinda confused with what you're asking as well. Perhaps you could draw a diagram in paint or something? heh

 

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 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.

Backspacing: 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.

This is all from CCW.

 

For example if you have an 8 inch wheel with a +24mm offset. An 8 inch wheel is actually 9 inches wide....

The wheels I'm looking at right now are 15x8, 5.5 inch BS and +27mm offset. So in layman's terms, one could say they are basically a 15x9 with 6.5 inches of BS?

 

No, you do not need to know the offset and the back spacing.

Using backspacing alone will determine your clearance to suspension parts and such inside the wheel well, regardless of width.

Using offset alone will determine the scrub radius.

If they're advertising 5.5" BS and 27mm offset on an 8" wheel, one of those measurements is inaccurate. Perhaps it's 5.5" measured from the back of the wheel to the mounting surface, whereas the 8" claimed width is inside the bead seat.

Where ever that statement of an 8" wheel being 9" came from, is wrong. A wheel's stated width is inside the bead seat, where it matters to the tire.

 

If they're advertising 5.5" BS and 27mm offset on an 8" wheel, one of those measurements is inaccurate. Perhaps it's 5.5" measured from the back of the wheel to the mounting surface, whereas the 8" claimed width is inside the bead seat.

It's close enough, depending of thickness of rim edge.

8" inside width + both edges about 1/2" each gives total width to 9"
Half of that is 4.5", so with 5.5" backspace it gives to +1 inch offset, which is 25.4mm.
So those rims with 27mm offset have just little bit thinner edge than usual 1/2"

Picture of last_in's post is correct, back spacing is measured innermost point of wheel to mounting surface and offset is measured centerline of wheel to mounting surface.

27mm offset will fit just fine, because almost all of our trucks stock rims have 25mm offset.
Only problems with about 25mm offset could be with short and wide rims: I think at 15x10" will hit to in somewhere of front suspension or steering, but 20x10" with same offset probably will fit without any problems.

:sorry: for bad english

Juha

 

Lol, Caulk just came in and confused me all over again.

I'm just trying to figure out if the wheel I mentioned a few threads above will tuck under my fenders and not stick out any.

 

This link should help.

Offset and Backspace - How Do They Relate?


Which wheel (dimension wise) from above are you trying to compare? We would be happy to help.

-Matt

 

Which wheel (dimension wise) from above are you trying to compare? We would be happy to help.

The 15x8 with 5.5BS and 27mm offset, I plan on wrapping a 295/50 around it with the hopes of it all tucking under the rear and not sticking out past the fenders any.

Only problems with about 25mm offset could be with short and wide rims: I think at 15x10" will hit to in somewhere of front suspension or steering.
Juha

No problem there, I'm planning on running a 15x7 up front with a 215/75. That is what came stock, I just have ~2 inches of wheel well hanging over the tire. So I'm wanting to run a bit less backspacing up front to stick the wheels out to fill up the wheel well better.

:sorry: for bad english

Se ei ole ongelma kiitos kuitenkin.

 

http://www.dakota-durango.com/forum/showthread.php?t=126788

also, dont go too crazy with changing them.
http://www.dakota-durango.com/forum/showthread.php?t=116615
it was figured out the reason this happened was a cheaper hub and backspacing that was way off caused a failure

 

Wow dude, that sucks...that was a nice-ass Dakota.

I read through all 10 pages of that, and I don't think it was just the wheel's backspacing. I think it was the combination of the big and heavy tires, the weight of the truck, the lift, and the wheels.

Either way, my little GEN-II weighs nothing compared to your 4x4 rig. So I don't think and inch less backspacing up front is going to hurt anything, not to mention my tires are WAY smaller and weigh a 1/3 of what your 35s did. And the rears I'm wanting to run have only 1/2 less back spacing than the factory 16x8 wheels. I don't think 1/2 is going to make much of a difference. If anything, I would think placing the load more towards the center of the wheel, as opposed to the outside edge, would make for more even load distribution. Thus applying less force to the bearings and more on the mounting flange of the wheel it's self.

 

not my truck, but another ct member.
and yes, it was due to a number of things, but that shows you how bad it can go. you can be buying hubs every year if you go too far out of stock speck
they make is so the force is centered on the bearings. you need to remember your going to move all the load.
but 1" i would run it fine
not to mention people run R/T rims on gen 2 fine