Rally Wheel Weirdness??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sick472 · 02-21-2020, 10:39 AM

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** · 02-21-2020, 10:57 AM

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 · 02-21-2020, 11:46 AM

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** · 02-21-2020, 12:04 PM

I thought you measured where the bead of tire rested.

sick472 · 02-21-2020, 12:20 PM

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

02-21-2020, 10:39 AM	#1
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	Rally Wheel Weirdness??? 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. Attached Images __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20

02-21-2020, 10:57 AM	#2
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,862	Re: Rally Wheel Weirdness??? 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. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

02-21-2020, 11:46 AM	#3
cebra Registered User Join Date: Jan 2018 Location: Durham, North Carolina Posts: 782	Re: Rally Wheel Weirdness??? 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. __________________ My Daily Driver Build: http://67-72chevytrucks.com/vboard/s...d.php?t=755668

02-21-2020, 12:04 PM	#4
Jcfcamaro Registered User Join Date: Jul 2015 Location: Fairfax, Missouri Posts: 1,054	Re: Rally Wheel Weirdness??? I thought you measured where the bead of tire rested.

02-21-2020, 12:20 PM	#5
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	Re: Rally Wheel Weirdness??? 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 __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.