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'48-'52 Steel Wheel Backspacing

Started by tower154, April 09, 2020, 07:27:13 PM

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tower154

Thanks to Jeff Friedman I have narrowed down the wheels that should fit my '49 Club Coupe by part number.  However, none of the wheels that I can find have the part number stamped on them, and usually only have Kelsey Hayes 15x6 and the date code stamped in them (some 15x6-L).  From what I've been able to deduce (thanks to Bill Ingler), I'm thinking that the backspacing (backside rim lip to mounting lug hole) should be about 3-7/8".  I've found some Cadillac 1950 wheels with 4-1/2" backspacing, but I don't think that these are correct for my car.  Can anyone confirm the correct backspacing for the '48-'52 (maybe through '55) 15x6 5-5" steel wheels for a Series 61 (also I believe Series 60, 60S, 62, or 63)?
1949 Series 61 Club Coupe
1949 Series 62 Club Coupe

Caddieman53

My Master Parts Book says that years 1948 thru 1955 the wheels are all the same for series 60S, 61 and 62. Except Eldorado. The 1950 wheels should fit your car.
P. W. Allen

53 Cadillac Coupe 6237X
Twin Turbine

tower154

#2
Thanks PW.  I hesitate due to the fact that the "except for Eldorado", and there is also mention that the Series 75 and 76 wheels are the same size but different as well here: http://www.jholst.net/tires-wheels/MotorWheelCat_1964a.pdf.

I was hoping to confirm the front spacing or backspacing on the rims before I ship them cross-country.  For some reason, the 4-1/2" backspacing doesn't seem right.  My logic is that we measured the front spacing on a 1947 rim that was a one year only and that had one year only sombreros.  The front spacing on the rims were 2-5/8" and the backspacing was 4-1/4".  If the 1949 sombreros stick out a 1/4" past the front lip of a '47 wheel, then the '48-'52 front spacing must be deeper.  Therefore, the '48-'52 backspacing must be smaller than the 4-1/4" backspacing on the '47, assuming that all the wheels have the same front and back lip and overall widths.  If so, a 4-1/5" backspacing must be an incorrect wheel.   Am I missing something?  These seem to be all over the place!  >:(

Compiled data so far:
15x6 5-5" Wheels
1947: Front Spacing - 2-5/8"   Backspacing: 4-1/4"
1949: Front Spacing - 3-5/8"
1950: Kelsey Hayes 15x6-L Backspacing: 4-1/2"
1953, 1954: Front spacing - 2-1/4". Backspacing: 4"
1955: Backspacing 4-1/8"

16"dia. Sombreros:
1947: Heigh from back to lip = 2"
1949: Height from back to lip = 2-1/8", Height of "Dog Dish" 2-1/2"


1949 Series 61 Club Coupe
1949 Series 62 Club Coupe

fishnjim

Interchange says the same thing, '48-55 same rim.   
They didn't stamp part numbers on the rims.   
And it's not like today's numbering.    If you have one, then there maybe stamping inside the tire side that will narrow down the "rim stock".   "Never" on the outside ,always concealed by tire.   Some of these are riveted and some not, so that should match as well.   I don't know what '49s are.   In that era, I suspect they're riveted but a guess.
That's how I went about getting rims for my later car.   They're pretty much all 15 x6 w. 5" bolt pattern rims.  We used to call them "big GM" back in the day - because they fit all the "big" cars.   So the only thing that changes is the rim stock which may affect the offset.   But appears offset's not a factor here or they would have different part numbers and interchange info.   Parts number are just for Cadillac internal control, the suppliers used a different system.   
Some of these rim stocks don't fit certain hubcaps.  That's your biggest concern.   They all will pretty much clear the drums.   So set back is only going to affect the alignment specs.   That can be worked around.  eg; You could put modern pickup truck 15" rims on it and they'd "fit".
Somewhere I have a list of rim codes but not finding it today.   I used to live where they made all the rim stock for GM and there's only so many and they go by a letter code, like "JJ" etc..   
I'd check with a few different tire places and see if they have any offset info.   If you want more confidence, but I think you're using today's system of measuring...
Or try all Cads or some parts place like that with '49 rims.   They may have one and can measure.   
It's far from certain that the rims on a vehicle this old are "original".   About the only way to tell is someone wrote on it when they took it off.   The parts yards usually only go by size. eg; I asked for 15 x 6 - 5  and they gave me 15 x7, so I had to send them back to find others.   The 7's would've fit but I had other 6's, so mismatch.   
Rear wheel well clearance was an issue too.  Probably not a problem here unless running full skirts.

tower154

Thanks Jim.  You are right on the money.  I think that the only way to be certain that the '49-'55 sombreros will fit is to measure the front spacing of a set that we already know work together.  So far, I haven't found a set that that someone has the sombreros on.  I'll keep searching!
1949 Series 61 Club Coupe
1949 Series 62 Club Coupe

60 Special

I have 4 wheels (not for sale) 1 1949 wheel with 4 3/16 backspace, 2 1951 wheels with
4 3/16 backspace, 1 1951 wheel 4 7/32 backspace. All wheels are stamped KH 15X6-L. These were all measured with a steel straight edge across the rim and the depth was checked with a 6" steel machinist scale. Hope this helps your quest!