tire stretch question
 

which one will have more stretch on a 7" wheel?

175/50-16 or 195/40-16?

175

It's very close. The 175 is 50 series, so more sidewall to work with. But the 195 is two sizes wider, and although the widewalls are much less meaty, it is a wider tire. Remember the middle number ("series") indicates the sidewall size as a ratio (percentage) in comparison to the first number (which represents tire width).

You might also want to disclose the make and model of the tires. Some run small, some run large, some run true to size and depending on the brand some stretch better than others.

If you go strictly by the numbers, the 175/50 will have about an 8% taller sidewall than the 195/40 BUT because the tread surface is narrower, more sidewall will be stretched to meet the bead.