front and back spacing stock steel wheels
Can anyone give me the front and back spacing for the stock steel wheels on a '54 Corvette? I am 550 miles away from my car or I would pull a wheel and measure it myself.
Don
Don
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Re: front and back spacing stock steel wheels
Joe,
I think that you should check your calculations for the backspacing.
Don,
Generally the gross width of a wheel is approximarely 1 inch larger than the net width.
I once owned a 15" X 5" Chevrolet & Corvette wheel stamped "15 X 5K", "54" and "8" (August 1954) that was riveted and had a 2 7/8" hub hole. I believe that this August 1954 wheel was either GM # 3707031 (with a 5/8" offset) or GM # 3714202 (with a 9/16" offset).
The gross width of the wheel measured about 6 1/32" (or about 6.03") in width. The backspacing measured about 3 5/8" (or about 3.63").
The offset can be measured as follows:
3.63" - 6.03"/2 = 0.62" (rounded off) = about 5/8" offset
Therefore, my August 1954 wheel must have been a "late" 1954 wheel, GM # 3707031.
This wheel measured 3 5/8" (backspacing) + 13/32" (thickness of metal hub area) + 2" (front) = 6 1/32" total gross width.
I have never heard of the term "frontspacing".
BTW, I still have a very nice set of four 1949-1953 Chevrolet wheels (GM # 3687980 with a 5/8" offset) that have their original paint with the white circular pinstripe in my collection. These wheels are are also a replacement for the 1953 Corvette wheel. If I removed the 5 hub cap clips that are riveted to the wheel they would be 1953 Corvette wheels (GM # 3699828 without the clips) except they are dated November 1951 as best as I can remember. I believe that the original 1953 Corvette wheels do have the 5 rivet holes, one between each lug hole.
I can easily measure the backspacing on these wheels, if necessary, but I assume it would be about 3 5/8". Enclosed is a photo below.
Dave
Last edited by David L.; May 12, 2015, 09:55 AM.Comment
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Re: front and back spacing stock steel wheels
Dave,
I think Joe might have been basing his numbers on the bead to bead measurement, not overall rim width. Also, Joe was almost certainly using a 9/16" offset (0.5625") vs. your 5/8" offset (0.625"). Both of you are right. Potato, potato. I don't know which is correct for my car, but I'm betting 1/16" doesn't make any difference worth worrying about.
It is good to have confirmation from two people regarding the numbers. What I want to do is install Dayton wire wheels, 6x15, with 205/75R15 Goodrich red-line radials. I'm keeping my stock rims, wheel covers, and bias ply tires for show. The question is... what offsets do I order on the wire wheels? BTW, that's 7" wide overall on the wire wheels. The 6" number is bead to bead.
Using overall width = 6" and 9/16" offset, for stock rims I get back spacing = 3.56" and front spacing = 2.44". The Dayton wire wheels, at 7" overall width, are available with back space = 4" and front space = 3". There is another version with 4.38" bs and 2.62" fs. I would be inclined to go with the 4"/3" version because it distributes the increased wheel width equally to the inside and outside. I would be interested in knowing what you think about this.
Don
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Re: front and back spacing stock steel wheels
Don,
I believe that the industry standard uses the gross width of the wheel for measuring backspacing (see attachment below).
The theoretical width of a P205/75R15 tire is 8.07" (205 / 25.4 = 8.07). The offset of a 15 x 6 wheel with a 4" backspacing would be about 7/16" or 1/2" (4.00" - 7.10/2 = 0.45", assuming gross width is 7.10") depending on the gross width of the wheel. Your original wheels have a 9/16" or 5/8" offset and I assume that your bias tires might be 6.70-15. Based on these assumptions when mounted on the car the inside face of the P205 tire on the 15 X 6 rim would be about 0.50" to 0.63" closer to the frame and the outside face of the tire would be about 0.74" to 0.87" further out. I think my calculations are correct but you should obviously check for yourself. I would think that you will have enough clearance to the fiberglass and frame but I do not know much about straight axle Corvette bodies.
Dave
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Re: front and back spacing stock steel wheels
Thanks for clarification, Dave. Your understanding is a level or two above mine regarding wheel spacing. You are correct in both your assumptions, and I believe correct about there being enough room for the 15x6 wires with P205s. I hope we're right. It's a $2240 bet.
DonComment
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Re: front and back spacing stock steel wheels
Don,
Before you invest $2,240 I would double check your computations as well as mine. Below is a scan of my sketch and simple computations.
Dave
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Re: front and back spacing stock steel wheels
Dave,
You are assuming the offset on the wire wheels is .44 to .50, correct? We don't need to guess about that, because I got my BS and FS numbers directly from Dayton. For the Dayton wire wheel I am considering, the outer rim width is 7". For this wheel, the BS = 4" and FS = 3". According to Coker Tire, the section width of a 205/75R15 redline Goodrich radial is 8". Adding another half inch to these gives BS = 4.5" and FS = 3.5" to the outer surface of the 205 tire. That's pretty much what you have calculated, so your guess about offset was pretty close.
Again, according to Coker the section width of a typical 670x15 bias ply tire (stock for Vette) is 7". Using your work product, that would give, for a stock steel rim, BS = 4.06 - 4.12 and FS = 2.94 - 2.88 to the outer surface of the tire.
That seems to me to indicate the Dayton wire wheel and 205 radial I am looking at pretty close to 1/2 to 5/8" closer to the frame and glass. I'll have my restorer measure it, but I can't imagine that would make a difference regarding clearance.
BTW, my results agree with your results. That's got to be a good thing, especially since I worked from Dayton's and Coker's information.
Thanks a bunch for your help. You've really gone out of your way to set me on the right path.
DonComment
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