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Joined: Dec 2002
Posts: 597
Oil Can Mechanic
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OP
Oil Can Mechanic
Joined: Dec 2002
Posts: 597 |
I'm having trouble getting 21" tires on my 21' Baby Grand. Are these the right size for the original rims? Any help much appreciated!
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Joined: Dec 2001
Posts: 845
ChatMaster - 750
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ChatMaster - 750
Joined: Dec 2001
Posts: 845 |
I can't speak from experience, but 75 Years of Chevrolet lists the 1917 Baby Grand as having 30 X 3 tires. In scanning the early years in this book, it appears that most, if not all, Chevrolets in the teens and early 20's had tire sizes in the 30 inch diameters. If you're attempting to install 21 inch tires, it may be a bit of a stretch.
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Joined: Jan 2002
Posts: 980
ChatMaster - 750
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ChatMaster - 750
Joined: Jan 2002
Posts: 980 |
I have seen 21" tires used instead of 30 x 3 1/2. The old system measured the outside diameter, in the newer system 21" is the inside diameter.
If you have old Chevrolets, other old Chevrolets will find out where you live.
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Joined: Dec 2001
Posts: 10,379 Likes: 1
Technical Advisor ChatMaster - 10,000
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Technical Advisor ChatMaster - 10,000
Joined: Dec 2001
Posts: 10,379 Likes: 1 |
According to my information the size for the FB was 33 inch by 4 inch. 
RAY Chevradioman http://www.vccacolumbiariverregion.org/1925 Superior K Roadster 1928 Convertible, Sport, Cabriolet 1933 Eagle, Coupe 1941 Master Deluxe 5-Passenger Coupe 1950 Styleline Deluxe 4-Door Sedan 1950 Styleline Deluxe Convertible 2002 Pontiac, Montana, Passenger Van 2014 Impala, 4-Door Sedan, White Diamond, LTZ 2017 Silverado, Double Cab, Z71, 4X4, White, Standard Bed, LTZ If you need a shoulder to cry on, pull off to the side of the road. Death is the number 1 killer in the world.
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Joined: Jan 2002
Posts: 1,623
ChatMaster - 1,500
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ChatMaster - 1,500
Joined: Jan 2002
Posts: 1,623 |
Better check the info on what was available on your car, looking particularly for what was optionally available. If you have it, look carefully at the Sales Literature for your model. It should also be mentioned in the Owners Manual and/or Repair Manual. Do not trust information in various books like "60 Years of Chevrolet" or "Coming of Age" on this type of detail, especially in the early years they are full of errors and omissions. For instance, the standard equipment tires for my '25 Roadster were the 30 x 3.5 (same as a Model T). But, optionally available was the 4.25-4.50 x 21" which my car has. This included different (optional) wheels and rims. It cost $25 extra in 1925, but I hear it was money well spent. The 30 x 3.5 is NOT the same size tire as the 4.50 x 21. It is true, however, that they are measured differently (outside versus inside). Possibly, the fatter, lower tire was optional on the earlier years, too - I don't know. I also know that it is a real struggle to mount a new tire on these old rims, especially if you have never done it before. It's very physical, and just plain hard to do! 
Chevy Guru
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Joined: Nov 2001
Posts: 19,758 Likes: 64
ChatMaster - 15,000
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ChatMaster - 15,000
Joined: Nov 2001
Posts: 19,758 Likes: 64 |
FYI,
The old tire sizes were indeed different from the modern ones. Today and back to the late 20s for some sizes and early 30s for other sizes the inside diameter the is the last number x21, ???x18, Y.YYx16 etc. The earlier gave the outside diameter as the first number. The second number was the sidewall height. Therefore a 30X5 tire used a 20" rim. A 33X4.5 used a 26 inch rim. Yes you have to double the side wall height subtract it from the outside diameter to get the rim diameter. Back then it was cyphering.
My owners manual for the '19 FB specifies 33X4 tires or 25" diameter rims.
How Sweet the roar of a Chevy four!
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Joined: Dec 2002
Posts: 597
Oil Can Mechanic
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OP
Oil Can Mechanic
Joined: Dec 2002
Posts: 597 |
I want to thank everyone for their responses. I pulled a legible 4.50 x 21" tube out of one of the old tires and that is why I had suspect them to be 21"s. The tires were completely illegible and I have no paperwork. I am going to give it one more shot this week and if I don't have luck, guess I'm going to have to go larger on the tires. Enjoy the rest of the weekend everyone. Thanks again!
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Joined: Dec 2001
Posts: 11,162
ChatMaster - 10,000
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ChatMaster - 10,000
Joined: Dec 2001
Posts: 11,162 |
Just a word of caution , a tube will fit more tires than one. they stretch and work for a couple of rim sizes.
Life's a long winding trail, love Jesus and ride a good horse!
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