Backspacing question

[Scarab]

This thread has changed direction a couple times, but with a 9” (4.5” B.S.) wheel it will move the tire centerline out 1/2” compared to an 8” (4.5” B.S.) wheel and should pull the sidewall off the frame about the same.
I’ll add this here as it’s posted on his other thread as well.
This would be compared to his existing tire and wheel setup and based on having 1/2” clearance to the frame.
You’re right, if he needs more room he can go to aluminum drums or add a small spacer.

View attachment 392242

thank you for the info. I am going to see. I may be wrong but I thought I would have only 3/16 of a inch from the frame as the tire is 11.1 instead of 10.4 which is on it now. Anyone want to buy some dimple GNX wheels with new 255/50/16 drag radials on them?

 

[1986 Buick GX1]

thank you for the info. I am going to see. I may be wrong but I thought I would have only 3/16 of a inch from the frame as the tire is 11.1 instead of 10.4 which is on it now. Anyone want to buy some dimple GNX wheels with new 255/50/16 drag radials on them?

You’re welcome.
It took me a while to make sense of things when I was looking into new wheels. Since I was ordering expensive custom wheels as well, I bought a couple cheep wheels off flea bay to help figure things out as it was cheaper than redoing the wheels or ordering more wheels.

The backspacing stays the same, but since the wheel is wider it pulls the inner sidewall away from the frame.
You’re right, if the wheel width and backspacing were the same, then adding the extra tire width would make it closer to the frame.

If you want to take the time to measure everything, here’s a wheel form they use.