Custom wheel backspacing

[fasteddie]

I’m in the planning stages of new custom wheels and tires on my bone stock 1978 F150. I’m looking at a set of 8 hole polished aluminum wheels. 15x8 or larger. The backspace on my original wheels is 3.5 on 15x6 OEM steel wheels. I’m asking for the correct backspace that would not have a clearance issue. I’m believe it’s going to be a 3.75 with a -18 offset on the 15x8’s. Is this correct? I have to order the wheels and I do not want to guess wrong and wind up having to send them back. Anybody out there with this same setup that can educate me will be awesome. Thanks in advance for your help.

 

[Fellro]

Most modern vehicles require more negative back spacing, meaning most of the wheel is behind the bolting face. For your vintage truck, you want to keep a bit of positive backspacing, keeping more of the wheel extending outward from the hub face. I don't see a 18" negative being a likely actual measurement for an 8" wide rim.

 

[fasteddie]

18 millimeters which is around 3/4 of on inch is the way I read it the manufacturer size charts. I understand 18 inches is out of the question. I believe an eight inch wheel with 3.75 back space and a 3/4 inch offset will work on my 1978 F150 2wd. Do you agree?

 

[Fellro]

Ah, you mixed units on me. That makes more sense. It should work fine.