Backspacing - Am I missing something?

[Hammered]

The car is a '67 Firebird with stock rearend. I want to run 17x8s with 255/45s in the rear and 17x7s, 235/45s in the front. My clearance dimensions from the drum face in the rear are 7" to the high point on the inner housing and 4 1/8" to the pinchweld lip. I can gain 1/4" by trimming the lip, but don't want to roll it because I'm running the lip chrome and shouldn't have to anyway.

Here's the question, if I run 4 3/4" backspacing like every one else, I'll have 1 3/4" clearance to the inner well and the tire will come to about 1/2" of the outer most part of the quarter? I figure I need about 5.5" backspacing to get it tucked in to where it won't hit the lip. Does this sound right??? If so, what should I do if I want to put discs on down the road? Lastly, how about the fronts?

Finally, what do you guys think about the Boyd Two Tone for this car: http://www.billetwheel.com/cgi/wheels.cgi?cmd=show_image&path=Gotcha_Series&img=28&tn=1

I know it's the same as the Intro, but the Intro center cap looks too much like a spindle bearing dust cap. I also looked at the BS Street Stars, and SLX37, Intro Hammer5, Budnik Famosa and others but keep coming back to this wheel.

BTW, I've got Hotchkis SB springs on the front and will be getting Hotchkis leafs on the back soon.

Thanks,

John

[barno68]

Take a look at your tire height compared to stock. It looks fairly close. Stock rims were 14x7 with near zero offset, so with the wider tires I can't see why you would need to move that rim in two inches to compensate. People running 4.75 backspace are running 8" rims, so you can adjust that down for a 7" rim. An 8" rim in the back is no issue, I think I ran a 4.5" back space with 225s with tons of room.

[Hammered]

I think I figured out part of my problem last night. I took a rough measurement of the rear and I think it's 61" versus the 60" rear that the Camaro came with. I guess that's why Pontiac called their cars Wide Trackers. I will double check tonight, but that would turn 4 3/4" into 5 1/4" If I add 1/4" to account for my car's specifics and 1/4" for future disc upgrade, that's a total of 5 3/4" backspacing on an 8" rim. Is that too much?