Model T T tire sizes ??

[Moxie26]

Looking for standard tire sizes , front and rear , and availability. Thanks in advance.

[George House]

If you’re asking the sizes of Pneumatic tires Ford factory installed, there are two front sizes and two rear sizes. The earliest were 30 X 3 1/2 front and 32 X 4 1/2 (or 5) rear. Later they went to 4.50/4.75 X 21 fronts and 6.00 x 20 rears.

[Wayne Sheldon]

There are actually three tire size combinations common to model T Fords (and a whole bunch of variations in the wheels themselves!).
Non demountable clinchers are the only ones which used different sizes front and rear. On USA built cars from 1909 model year until end of production in 1927, USA non-demountable clincher fronts were 30 X 3 size. Non-demountable rears were 30 X 3 1/2.
Canadian built non-demountable wheel model Ts were 30 X 3 1/2 front and rear.
Demountable rim clincher tires were 30 X 3 1/2 both front and rear. Both on USA and Canadian production.

High pressure and clincher style tires were measured "outside diameter" by profile inward. (Which creates a lot of confusion on rim size!)

Later "balloon" style lower pressure tires began by using "outside inward" measurements, but soon after switched to the more common still today method of measuring the rim and inside bead of the tire (inside diameter of the tire!) by profile outwards. Actual rim/bead size is the most important size number for fitting tires, and therefore basing the tire size on that figure is less confusing.

Regardless. The later model's balloon size tires were 21 inch rim size, by somewhere between 4.25 and 4.50 profile (seemed to vary during production and different sources of information).
The tire size was the same with the balloon tires regardless whether the wheels were wooden spoke or welded wire spoke.

[Kerry]

Wayne, good information but not really covering the question of TT's.

[DHort]

I guess T T is the same as TT. I was as confused as Wayne.

[Moxie26]

Thank you George House for you knowledge of Ford T Trucks.

[Wayne Sheldon]

Ah yes, TTs, a whole other can-o-worms tire-wise.

Except for some amount of Canadian production, which used I think it was 20 inch rim size X about 6 front and rear? Front and rear were always different. I don't know for sure about some of the timelines. I have a general idea of what years some options were available, but I may be off a year or two either way.

After-market wheels added other and often odd options on both cars and trucks. I avoided car after-market options, because they weren't really common (except for the earlier demountable Firestone type wheels?).

In 1918 and 1919 TT model years, Ford factory basically had only one offering. That was non-demountable rim pneumatic 30 X3 on the front, with solid semi-soft rubber tires on the rear. I am not sure of the rear "rim" size, but it was near 23 inch.
In late calendar 1919, likely early 1920 model year, demountable fronts using 30 x 3 1/2 were offered as an option.
Solid rubber front tires in either demountable or non-demountable rim type wheels as far as I know were all after-market offerings. They were fairly common on earlier TTs.

In 1925, 21 inch rim size were offered on the TT trucks just like the 21 inch rim wheels for the cars. As far as I know, the welded steel spoke wheels were never officially offered on the TT truck from the factory.

About 1920, along with the demountable rim front wheels, Ford offered optional pneumatic rear tires on demountable rims. The rim size was 23 inch (I think?), by about five to six inch profile.

A few years later, I think either 1924 or 1925 (several people have told me it was earlier than that?), another optional rear wheel and tire was offered for the model TT truck. That being a 20 inch rim size demountable and about six inch profile.