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Old 08-15-2021, 11:09 AM   #1
MyTwOfOrDs
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Default 20 inch rims

I got 20" duals on 46 3 ton. Can 8.25 tire go on where 7.5 was? I assume its just a width diff. 6" rim. Are these able to balance?
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Old 08-15-2021, 11:29 AM   #2
alanwoodieman
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Default Re: 20 inch rims

8.25 will fit, you will actually go faster! also your speedometer will be off just little
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Old 08-15-2021, 02:14 PM   #3
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Default Re: 20 inch rims

I find getting these balanced a real bugger
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Old 08-15-2021, 02:17 PM   #4
Bob C
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Default Re: 20 inch rims

The 1941-48 Service Bulletins shows 7.50 and 8.25 on 7" rims.
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Old 08-15-2021, 04:48 PM   #5
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Default Re: 20 inch rims


That is one very neat old 1941 Ford Truck with Patina.
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Old 08-15-2021, 08:42 PM   #6
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Quote:
Originally Posted by Bob C View Post
The 1941-48 Service Bulletins shows 7.50 and 8.25 on 7" rims.
My 7.5s are on 6's
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Old 08-15-2021, 09:26 PM   #7
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Default Re: 20 inch rims

The '47 two ton had wider rims so I went to 8.25s. The '37 ton and a half is on 7.50 x 20s. I'm a tire guy, I vote for the 8.25s. The extra circumference is a big plus on modern roads
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Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1947 Tonner Pickup (red) mostly stock with exception of a cummins 6at turbo diesel, 1946 Tonner Pickup (green) with 226 cu in 6 cyl flathead, 1979 Toyota landcruiser wagon, completely encased in 1947 Ford Jailbar sheet metal. Ok, cornbinder rear fenders..... 'Rusty ol' floorboards, hot on their feet' (Alan Jackson)

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Old 08-15-2021, 09:30 PM   #8
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Default Re: 20 inch rims

And I just found another pic of the '47. I love the 8.25s
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Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1947 Tonner Pickup (red) mostly stock with exception of a cummins 6at turbo diesel, 1946 Tonner Pickup (green) with 226 cu in 6 cyl flathead, 1979 Toyota landcruiser wagon, completely encased in 1947 Ford Jailbar sheet metal. Ok, cornbinder rear fenders..... 'Rusty ol' floorboards, hot on their feet' (Alan Jackson)
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Old 08-15-2021, 09:31 PM   #9
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Default Re: 20 inch rims

Watch out for sidewall rubbing on your duals with larger tires. Some stock rims do not have the spacing for the wider widths. Newc
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Old 08-16-2021, 01:26 AM   #10
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Default Re: 20 inch rims

good advise ^^^^, can not let the sidewalls touch, makes heat, go boom. I just retired from a construction company, 5 axle dump trucks, semi's to haul equipment, never balanced any truck tires. seems wrong to me, but 30 years of drivin them...I guess it works
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Old 08-16-2021, 08:11 PM   #11
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Default Re: 20 inch rims

Quote:
Originally Posted by MyTwOfOrDs View Post
I got 20" duals on 46 3 ton. Can 8.25 tire go on where 7.5 was? I assume its just a width diff. 6" rim. Are these able to balance?
Before giving an answer to this question, we need to know how the 6” width measurement is determined. Are you measuring across the rim lips, or down inside between rim lips. It matters. The National Wheel and Rim Association (NWRA) measurement standard used during the 1930s, and carried on by Ford in the Green Bible, was to measure across rim lips. In the 1940s the NWRA changed their standards to record measurements down inside across the inner base rim. Thus an early 6” rim is today called a 4.33” rim, and an old 7” rim is today a 5.00” rim. The Green Bible is the only reference I have that cites an 8.25-20” tire as appropriate for what is a current 5.00” rim. Most references cite it for a current 6.00” or wider rim. Never on a 4.33” rim. Stu
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Old 08-16-2021, 09:30 PM   #12
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Default Re: 20 inch rims

I would follow the road Stu has paved for you. He knows this subject like no other.
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Old 08-16-2021, 09:55 PM   #13
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Default Re: 20 inch rims

The size I gave in post #4 are the old numbers. The Service Bulletins shows
tire size 8.25x20 wheel size 5.00-S (20x7) .
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Old 08-17-2021, 02:25 AM   #14
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Default Re: 20 inch rims

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Originally Posted by Bob C View Post
The size I gave in post #4 are the old numbers. The Service Bulletins shows
tire size 8.25x20 wheel size 5.00-S (20x7) .
Yes, Ford was consistent with itself on the use of an 8.25-20” tire on an old 7” (new 5.00”) rim width. Just inconsistent with the industry as a whole. Given that the member’s truck is a 1941 there is a good chance he has 4.33” wide rims that no reference says should accept the 8.25-20” tire size. Add to this the above mentioned concern about shallow wheel offsets and the risks of rubbing on the dual rears.

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I would follow the road Stu has paved for you. He knows this subject like no other.
Thanks Owen. Stu
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Old 08-17-2021, 09:26 AM   #15
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Default Re: 20 inch rims

A '40 1 1/2 ton I used to have had 8.25's on the front and they rubbed the fenders when turning. Replaced them with 19.5's before I sold it.
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