Wheels with unknown backspace

[DaveMueller]

I found a set of wheels on Craigslist and have done the required searching on the difference between backspace and offset.

The wheels are American Racing 44-5885, the specs say 15x8 and -19mm offset. How do I know what backspacing they are?

I'm looking to put narrow tires on my CJ5 for better snow traction. No lift, hoping for about 30.5" to match the current tires.

Thanks

 

[BusaDave9]

Those wheels have 3.75 inches of backspacing. The offset is measured from the center of the wheel and backspacing is measured from the inner surface of the wheel.

19 mm = .75 inch

 

[DaveMueller]

Those wheels have 3.75 inches of backspacing. The offset is measured from the center of the wheel and backspacing is measured from the inner surface of the wheel.

19 mm = .75 inch

Right, so how did you figure 3.75? Is there a standard backspace for a 15x8 wheel?

 

[BusaDave9]

Correction the backspacing is 4.75 inches.
The offset is 19 mm (.75 inches). That means the lug nuts are .75 inches from the center of the wheel. The wheels are 8 inches wide. Therefore the surface of the wheel that mounts to the hub is .75" from the center.

In the above picture the offset is .75 inches.
The width is 8 inches.
The backspacing is half the width (8÷2=4) add to that the offset (0.75") and you get 4.75 inches for the backspacing.

https://tires.tirerack.com/tires/Wheel%20Offset%20And%20Backspacing

 

[jp360cj]

Correction the backspacing is 4.75 inches.
The offset is 19 mm (.75 inches). That means the lug nuts are .75 inches from the center of the wheel. The wheels are 8 inches wide. Therefore the surface of the wheel that mounts to the hub is .75" from the center.

In the above picture the offset is .75 inches.
The width is 8 inches.
The backspacing is half the width (8÷2=4) add to that the offset (0.75") and you get 4.75 inches for the backspacing.

https://tires.tirerack.com/tires/Wheel%20Offset%20And%20Backspacing

Busa, you right the 1st time, a 15x8 with a -19mm offset will have a 3.75" backspacing.

As you said, the 19mm equals 0.75". A negative offset moves the lugs inward (subtracts from backspacing), and a positive offset moves the lugs outward (add to backspacing).

The 8" width is measured from bead to bead. The backspacing is measured from the rear edge of the wheel. Typically a wheel will have 1/2" on each side between the bead and outer edge, so a the overall width is 1" wider than the bead width. This means that an 8" wheel with have an overall width of 9". Zero offset would be (9 / 2) = 4.5" backspacing.

Subtract 0.75" from the 4.5" backspacing for a -19mm offset wheel to get a 3.75" backspacing.

OP, search for "backspace offset calculator" and there some online where you plug in your specs and it will give you the backspace, or vise versa.

 

[DaveMueller]

Riiight. So I'm good to go to put these on my CJ5, right?