Wheel offset vs backspacing

[wanderer]

I have been looking at this website that sells wheels and tires and packages. All of their wheels list a positive number. But they call it offset which if I understand. Correctly would pull the wheels in closer to the frame. This doesn’t make sense to me. But if it is backspacing then it would be pushing the wheels out. Does that make sense?

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[Gobi Wan K]

Well, yes and no. Offset is simply the amount the wheel mounting surface is from the centerline of the wheel. Backspace is the distance from the back flange to the mounting surface. So an 8 inch wide wheel with a 4 inch backspace would be a 0 offset. Yes, a positive offset means a wheel will likely be further in but that isn't necessarily the case with backspace. A 4.5 in backspace on an 8 inch wide wheel would still bring the wheel in. You kind of have to look at the numbers separately because although they interact, they don't tell a good story together. Also. Offset is usually expressed in millimeters where backspace is often in inches as long as the width of the wheel is in inches. Just a little more confusion thrown in for fun.

 

[Broke Owner]

Here you go

 

[Freebooter]

Ralph.......... it can be confusing. From your factory wheel, Rubicon has a 44mm offset and a Mojave has 37mm with a 7.5" wheel So if you choose a wheel with a smaller offset number, your wheel is going out. So a 12mm offset from a 44mm offset is moving your wheel out 32mm or an 1.25". So from 44mm to a 0 offset is moving the wheel out 1.73". And from 44mm to a -12mm offset is moving the wheel out 2.2". This is just offset factors and with the same width wheel. If you go with a wider wheel, that can push the wheel out further. I had a 7.5" wheel and went to a 8" wheel. 1/2" bigger so a 1/4" further out and a 1/4" further in if the offset stays the same. Most Mopar replacement wheels are generally 12mm that moves the wheel out enough to keep the inside of a wider tire about the same location as factory so nothing rubs lock to lock. Now this is all mathematical formulas. So change one factor and it changes how much your wheels sticks out, goes in and looks. Decide how much you want your wheel to stick out and go from there. Good luck!

 

[Stylinhonda]

Great info! Looking at a 17x9 with 4.5 BS and -12mm or a 17x9 with 5.0 BS and +1mm. Hard to decide!

 

[Silverslayer]

Great info! Looking at a 17x9 with 4.5 BS and -12mm or a 17x9 with 5.0 BS and +1mm. Hard to decide!

That is a -12 17x9 4.5bs, 285 tire width. For me personally I would've liked closer to 0 offset but the deal on the wheels was too good to pass over a half inch. Now I just need to do a bit of lift for it to look better IMO, oh well, could have worse problems lol.

 

[Stylinhonda]

Thanks for the pics. So would the 5.00 BS with a -12 offset stick out more or less than that with the 4.5 BS?

 

[Freebooter]

the -12 offset wheel will stick out a 1/2" more. Silverslayer has a 11.5" wide tire on a -12mm offset wheel. I have a 12mm offset wheel with a 12.5" tire. Here is the math on my situation: factory wheel 37mm offset with 11.5" tire: equal with edge of fender. New wheel 12mm offset with 12.5" tire. 37mm - 12mm=25mm or .98" going out from wheel. 12.5"-11.5"=1" for tire. 1" divided by 2 = .5"; .5" on inside; .5" on outside for the wider tire. So, .5 (tire) + .98 (wheel) = 1.48" further out than factory. Look at the picture, about 1.48" out past the fender.

 

[Nine Ball]

Just use a simple online calculator to convert between backspacing and offset. There are a few online like this one: wheel offset backspace calculator

Backspacing is easier for most to visualize. More backspace means the wheel moves inward towards the frame.

Offset is more commonly used nowadays. A higher value offset moves the wheel inward towards the frame. Positive offset wheels have more backspace than negative offset wheels.

 

[Stylinhonda]

Thanks again for the info. Looks like I may want to go with the +1 with a 5.00 back spacing. I like the tire to stick out a bit from the fender but not too much. Trying to find a picture of a 17x9 with the -12 mm offset and 4.50 BS. Found one but it was a side shot, hard to tell unless you get a shot from the front or back!

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