f20 rear tire size

Hello, I just bought a F20. It is in pretty good condition on 38 inch cutoffs right now but came with a set of 36 inch F & H rear wheels. I was wondering what size tires other people had on their tractors. The rims only measure 8 inches accross the bead. I have 11.2x36 on some farmall SC"s but was wondering if anyone had mounted larger 12.4 or 13.6 size tires on the spoke wheels? This tractor has a whole different look with the 14.9x38 tires on it right now, only have 28 inch rubber on my other F20. Would plan to use the tractor some for plowing or light hay field work so I would like to get the largest size tire that fits well and looks correct. Thanks, Mike

I had an F30 one time with 13 inch rubber if I remember right. They were the old turkey track tread and I put 7.50s on the front to make it set level. Yeah, It looked good, but that was a 30.

Just a word from stuff I remember:
36" tires were one of the standard sizes from the factory. This was probably the smallest rim that would go OVER the brake drum. The problem with this is that the outside diameter is much larger than the 40" standard steel wheels. The tractor became much faster on 36" rubber. I once ran an F-20 on 36" rubber next to an F-12 on 40" rubber, and in second gear, the F-20 was neck-and-neck with the F-12 in third (factory specs: 4 mph). Since rubber wastes less power than steel, the rubber-tired F-20 would pull two 14" plows in second gear at this higher speed, with no difficulty at all. Sometimes, it would even plow in third, which I estimated at maybe 4-1/2 mph. In really light soil, and not too deep, I sometimes got it to pull in 4th (a bucking bronco at that speed, probably about 5 mph). I never got to use an F-20 on steel, but I spent a good 10 years on a steel-wheeled 10-20, which had about the same horsepower, and that would pull two 14" plows through thick and thin in second gear (about 3 mph), but almost nothing in third gear (just over 4 mph), because the lugs wasted so much power. I assume the F-20 would have performed about the same on steel.
The smaller tires that you sometimes see on F-20s, including in the sales brochures, apparently would not clear the brake drums, so the wheels had to be kept turned out. This made for a VERY wide tractor. The ground speeds would probably have been much closer to the original specs on steel wheels. I would imagine that, given the extra power to the ground made possible by rubber tires, the tractor with the smaller tires might have pulled a couple of 16" or 18" plows, maybe 3 12", but at somewhere between 3 and 3-1/2 mph. All guesswork, so take it as thinking outloud. Sometimes I get my kicks in my old age just doing this kind of "armchair engineering."

I put 11.2 on mine and they are look and work just fine,12.4 would look better though.Kind of wish I'd gone with those.

Any ideas on how fast the 36 inch rubber would be on a tractor with the factory fast forth gear? I thought that I was getting about 7 mph with the 28 inch tires but I never actually checked it very close. The new F20 which came from western WA actually originally came from Nebraska so it has almost no rust issues. I was originally only going to use it as a parts source to finish the F20 I already had running but now I leaning towards fixing both but maybe putting the 36 inch tires on the fast forth tractor. Sounds like I need to start looking for 12.4x36 tires.

I have a '39 that has 13.4 x 36 tires on it. I'm fixing the brakes right now. It has early model cutoff wheels on it. When I put it back together I have the correct late model cast centers with the 2 piece bolted rims going on it.