Why did old-timey cars have such skinny tires?

[zoid]

@ryanl

This threadis about historic grand prix racing cars, but it’s relevant to the OP.

Also, keep in mind that Model Ts and other cars of the period were not high performance machines. The Model T’s engine output was somewhere around 20 horsepower. A wider tire, by virtue of increased mass, would likely have diminished certain performance numbers (e.g., acceleration and braking distance).

This has got to be part of the answer. A thin, light tire has less rolling resistance and less angular momentum so it’s easier to get turning.
Today’s cars don’t have as much of a problem with power as much as getting all that power to the road, so when you have plenty of power you need wide tires with a lot of grip.