Why are model T tires different sizes front and back?
The skinnier tires on the front were cheaper. Many low priced cars of the early T era did the same thing for the same reason.
Ford published an article in an early edition of Ford Times making other arguments about lighter steering etc, but the real reason for nearly anything on the Model T was saving money to increase profits.
Many cars around 1910 did the same thing including Packard. They were not trying to save money evidenced by when they went to demountable rims they had to carry 2 spares. With them I believe it was a steering ease issue.
We had a similar thread a year and a half ago. As shown by the article "George in Cherry Hill" posted, many cars, including several "high end" autos used a lower profile front tire:
Ford wasn't the first to go with two tire sizes with the 1909 Model T. Other carmakers supported the theory:
The marketing excuses seem quite lame. The real reason is probably money, the root cause of almost everything. The chance of punctures being reduced is bull. a smaller diameter tire will actually increase the possibilities by rolling over the ground more times than a larger tire. The weight reduction is also lame, if you have to carry two spares you add more weight. Steering differences should be negligible. I suspect it was cost savings and better profits since spare tires were probably sold as options. They just made you buy another spare.
You would think that the front of the car is heavier than the back. However, notice how small the front spring is in comparison to the back spring? The tires were made to carry the load on the car. It was not necessary to have as large tires on the front as on the back. Saved a few pennies on the rubber.
Then along came the de-mountable rims. Now it was more economical to have one spare tire and one rim than two, and so the front tires were the same size as the rear.
All good thought's and idea's except the Canadian T's had 30x31/2 all around from the start? Bud.
An old timer once told me that the reason was the poor roads. The smaller front tire cut a narrower path through the mud and/or sand so it offered less resistance and actually helped to distributed the resistance so the drive wheel with the wider tire had less of a path to cut through. Kinda makes sense if you are slogging through 6" of mud or sand.
The tires on the front were the same diameter as on the rear. This was compensated for by larger diameter wheels on the front.
It was once explained to me by my uncle, an avid car guy born in the late 1890's that the early tires were basically very thick inner tubes with little side wall strength and therefore would roll from side to side more that the tires we know of today. A shorter tire on the front would therefore tend to roll less than a taller tire when making turns. As tire technology improved in the late teens and twenties, the car manufacturers gradually moved away from this practice. At least that was what I was told.