Rally Wheel Weirdness???

[sick472]

I'm sure I am over thinking this, but how come my old CK stamped 15x8 Rally wheels seem to have a 4-1/4 backspacing?

My research indicates that they were all 4" BS. I am guessing that "back spacing" is a loose term and my brain only works in finite values? If I drop my straight edge into the outer lip, I get 3-7/8" and I'm pretty sure BS is measured from the outer edge to the hub mating surface anyhow and this yields 4-1/4" BS. Hmmmm???

My real concern is that I am using these old wheels to determine where I want my new wheels to live (~2" wider stance). If I'm "doing it wrong"...I need to know now before buying all new shoes.

[special-K]

Yes, you do measure from the outer most lip. Just lay a straight edge across the wheel and measure to the mating surface. So, you are correct, 4 1/4" B.S.

[cebra]

Are you sure you are measuring the 8" part right as well? That looks similar to how a 7" wheel looks and not how my 8" wheel looks on the part where the lug holes are. I am not a wheel measuring expert at all but I did drive a long way for a guy that said he had a 15x7" rally wheel and he measured wrong and it was a 15x6". Unrelated but 15x7" are hard to find, it took me months to find 1.

[Jcfcamaro]

I thought you measured where the bead of tire rested.

[sick472]

You have made a good point Cebra, but I am 99% sure it's an 8" wheel. It still has a tire on it, so I have had to back into the wheel width by measuring the overall tire width and subtracting measurements taken from the outer tire sidewalls back to the rim.

Maybe my research is off...I just found this...

http://67-72chevytrucks.com/vboard/s...d.php?t=462895

It says the 8" wheels had a 4-1/4" BS. It seems most posters just say 4" BS for the 8 inchers.

JCF - I though that at first too. BS is measured from the extreme edge, but the wheel width is measured from the insides of the bead lips....

Here is a good short read on wheel measurements...

http://67-72chevytrucks.com/vboard/s...d.php?t=463017