Backspacing calculation cornfusion

[shadango]

 

Ok....I pulled one of my back rims....a chinese knockoff (far as i can tell) of a Weld drag lite.

I say knock off cause it is marked "made in china" and  doesnt say weld anywhere on it.

All it says is  T-531.

Anyhoo.

Trying to check the size and backspacing in prep for new tires....

The wheel is stamped 15x8.0  and then says   0 offset

Now from what i can find online, this should be a 4" offset wheel.

But I took a straight flat piece and laid it across the edge of the back side of the rim and measured to the mounting flange surface,.....and got 4.5" (give or take an 1/8")

For the front wheels (which are the same style and number but different size), they are 15x7, offset 0...but that backside measurement is 3 15/16".

Online I read an article that says that for a zero offset wheel, the backspacing is one half the width.

So WTF!!!

I also found that the wheel says "max diameter tire 28"...... so that will limit the size of tire I get obviously.

Thoughts on the backspacing question?

***update a couple years later -- LOL ---its an ULTRA "Nitro" wheel......

[Katfish]

I ran into this problem when looking for Mustang rims.  From what I found, the offset is related to the inside of the bead where the tire mounts, and the BS is to the outside of the rim.  From what I found the backspace is usually 0.5" greater than the offset.

Sounds like that's what you found also.

[72cudamaan]

I ran into this problem when looking for Mustang rims.  From what I found, the offset is related to the inside of the bead where the tire mounts, and the BS is to the outside of the rim.  From what I found the backspace is usually 0.5" greater than the offset.

Sounds like that's what you found also.

     Yes, you measure to the inner edge of the bead lock.