Replace Older Tires? and Spare?

[homeschoolin]

We upgraded the wheels on our fifth-wheel to 17.5 inch size in 2008 and had Continental HTRs (H-rated truck tires) installed (four tires plus a spare tire). These tires have about 40,000 miles on them since then. The spare has never been used. The tires have performed great and they still look good with plenty of tread and no sidewall cracks.

I am debating the need to replace these tires based on age. At the truck tire store where I bought the tires I received two different opinions. One said he would keep running the tires and the other said he would replace them just to be safe.

The tires have taken us through seven summer trips ranging from 5,000 to 7,000 miles. We will be leaving again in July for another summer trip of similar length.

I am leaning toward continuing to run the tires. These are heavy duty truck tires that are designed to run 100,000 miles on a commercial truck. I know that age, not mileage, is the issue, but the tires still look good.

I am particularly interested in hearing opinions from others that have upgraded to 17.5 inch wheels and higher quality tires.

How long do you run your tires?

If you advise replacing the tires, do you advise also replacing the never-used spare that has been hanging on the underside of the fifth-wheel?

[pnichols]

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.

[homeschoolin]

Thanks for the replies. I went ahead and replaced the four Continental HTRs with four new Double Coins. I kept the Continental that had been serving as a spare as it has never seen the pavement or the sun. Cost for the four Double Coins was a bit under $1,000 including mounting, taxes, valves, balancing, etc.

[MEXICOWANDERER]

I have had good-looking Michelins and BF Goodrich tires explode.

They looked good but later under the scrutiny of a large magnifying glass I saw axial cracking - tiny cracks circling the bead. Somehow I came to a conclusion that discovering such cracks foretell of an impending blowout.

I am also under an impression that 19.5" tires are better than smaller tires.

[midnightsadie]

think about it. running down the road at 60mph and a tire blows ,tears a BIG HOLE in the underside of your rig, cost to fix? in the thousands. IF fixable? tires age and ROT even though they look great. OH! that flat you had was on a sunday evening and 50 miles from no where and road service is closed. and its starting to snow. change the tires .

[Bumpyroad]

homeschoolin wrote:


If you advise replacing the tires, do you advise also replacing the never-used spare that has been hanging on the underside of the fifth-wheel?

on my motorhome I just bought 6 new tires and used the best old one as a spare.
bumpy

[Helimech]

I tend to look at the safety aspect over the dollars. Time to replace.

[donn0128]

Runem!

[Dick_B]

I'd wait until you had a blowout then consider replacing them. In the future rotate the tires including the spare. See www.michelinrvtires.com for their advice.