What is the maximum backspacing you can go on a '68 camaro? (front and rear)

I went with a 17x8.5 with 5.375 on the front of my 67. That may me a touch deep. I will mount them and check spacing when I get home later in the week. My rears are 6.125, I think on a 17x11 rim. I plan on narrowing my axle to meet the BS.

Brian

I have 15x8's with 4.5"bs on the rear which puts them about centered. I measured 11" from inner wheelwell to inner lip (6"from inner w/w to drum face and 5" from drum face to inner lip). No idea on wide fronts, I run skinnies.

Doug what size are your rear tires brand and do they rub the lip if load up with people???

I guess I'm just wondering if I can use a 18" x 9.5" wheel with a 275 tire and still keep it inside the fender well... and if so what backspacing to use?

A 9.5" wheel is probably a little too wide to stay inside with a 275.

Had 275/60 BFG'sfor a while, no passengers.
Had 245/60 Dunlop GT's for a while,no passengers but plenty of room
Now 285/60's McCreary's slight rub in turns, No way will they work with passengers.