15.5-38 or 13.6-38

[TRACTORNUTJD]

Looking at rebuilding an m from the ground up going to be putting aluminum pop-up pistons in it and so on should get it to the 50 horse range for an everyday user for plow days and farm chores my question is will 13.6-38 spin out and should I put 15.5 38 on there. It is going to need tires regardless and at least one rim

 

[matthies]

14.9 38

 

[Janicholson]

Agree. Rim will accommodate the mid size change. Jim

 

[Hayfarmer]

may depend on area you live in. I have 14.9x38 on my SMTA and needed a tire last fall. Dealer here doesn't stock that size so cost more to get it here. 15.5x38 more common not as tall as 14.9s but wider

 

[DR. EVIL]

The stock M cast rear wheel needs a DW style rear rim, and the 15.5x38's need a 14x38 rim, the do make a DW14x38 rim. A later style 400,450,560, 656,666,686 rims all fit 2-3/4 axles on the M, make sure to check axle keyway width and make sure the rear wheels are the same size. But the newer tractors have rear cast wheels with 8 holes and all take 14x38 double bevel rear rims that are much more common and cheaper.
We had 15.5x38 Good-Year Super-Torque tires on a 55 hp 450 Farmall, had good Traction when plowing. Used duals on it when disking loose ground. Using a 13.6x38 tire on a strong M it would be possible to spin-out. The 14.9x38 tire is an inch wider and about 2 inches taller than the 13.6x38 which gives it a wider and longer footprint, reducing chances of spinning out, and will fit on 12x38 rims, saving the expense of new rims. I'm in the same situation with my '51 M, 4 M&W Add Power sleeves & pistons, and 12-38/13.6x38 tires, one in very bad shape.

 

[Whiskey Bent]

14.9s look the best but are harder to find and more expensive.

 

[DR. EVIL]

As I said, I've been looking for new rear tires for Dad's '51 M he bought new, first tractor I EVER drove. He
put new 13.6x38 Firestone Traction Field & Roads on it about 1963 or '64, then promptly went out that fall and
drove over a broken steel post opening up cornfields with the mounted corn picker. The tire guy came back and
remounted one of the old take-off tires, a Gillette, like the old safety shaving razor company. It's not
survived the last 60 years well, has a zig-zag break down the center of the tread that you can probably see
tiny patches of exposed inner tubes, the other Firestone looks great. I can't afford a matching pair of new
Firestone's, but MITAS, based out of Charles City, Iowa make a duplicate of the 23 degree tread Firestone in a
14.9x38 size, I have no idea what they cost, or how available they are, but I'm putting a set on the M. I
priced 15.5x38 Firestone SAT-2's at my local Firestone store, I'd need 2 or 3 inches spliced into my rims to
fit them on, I've seen DOZENS of widened rims, mostly on pulling tractors, had a counter guy at POHL'S Tire
get REAL lippy with me about how dangerous it is mounting tires on welded rims. So I decided to mount tires
close to fitting my rims, I think they're DW12x38.

 

[BarnyardEngineering]

A 15.5x38 will crown up and look more like a 14.9x38 if you put it in a 12" wide rim.

 

[randy hall]

I have never owned a straight M with twelve inch rims, they have all been ten or eleven inches wide.