Replace Older Tires? and Spare?

MEXICOWANDERER wrote:
am also under an impression that 19.5" tires are better than smaller tires.

I don't know if it takes larger rims - like 19.5 inch ones - to gain longer and safer tire life.

What it does take to gain better tire life is a larger diameter in ones tires. A larger diameter means that the tire rotates less for any given speed ... which further means that each square inch of tread contacts the road surface less times per mile traveled and that each section of the sidewall that does the bending/bulging down at the bottom of the tire does this less times per mile traveled.

It doesn't take rocket science - only intuition - to figure out that less of these two things happening per mile traveled will result in longer and safer tire life:

1) Less tread contact per mile means less tread wear which means longer tread life.

2) Less sidewall bending per mile means less generated heat from flexing of the sidewalls and the resulting degeneration of the tire's materials that happens with heat.

I have always used tires on our trucks that had diameters larger than what came on them stock, including our motorhome. To do this doesn't always require larger diameter rims. New (good) tires are expensive enough as it is, so why pay for new rims too? Many times larger diameter tires for one's existing rims can be found. For instance, 16 inch rims have a whole bunch of tire's that can be found for them ... going way up in tire diameter as much as one could want.

I consider the resulting speedometer "too slow" speed readings from over-stock tire diameters as a trivial thing when compared to the improved tire life and safety that result.