Tire Wear Patterns

[nickmeloy]

Our current tires are GYM ST225/75R15, load range D. They are three years and four months old, and the date code on the tires is 0710. These tires have run for approximately 25,000 miles. The tire pressure is maintained at a setting of 65 psig cold inflation pressure. The CAT scale puts the total weight on the two axels at 7,300 pounds, with waste and water tanks empty. I estimate that our traveling weight is no more than 8,500 pounds.

When one places a straight edge across the tires, the depth of the outer treads is noticeable lower than the depth of the inner treads. That is, there is more tread in the center of the tire than there is on either of the outside treads.

Does this mean that I am running these tires underinflated for the load conditions under which I am towing the trailer?

[CDONA]

From what I've learned in life, yes under inflated.
An old trick to test real world needs on inflation, color a stripe 2 inches across the tire with chalk, then tow it a short bit and see what wears off first, adjust pressure.
Repeat as needed.
Is there a more modern way?

[Phoenix]

You state that the tires are load range D, and they are inflated to 65 psi. Therefore, there isn't much you can do, since you are already running the maximum rated pressure.

The chart at the bottom of this post is from a recently prepared summary of GYM tire failures from the tire failure poll. The first numbers (e.g., "3-4") indicates the tire age in years, and the number after the equal sign is the number of tire failures reported for that period. As you can see, GYM failures seem to peak in year three, so it's probably about time to start tire shopping. Besides, if you've towed 25,000 miles, and your Marathons are three years old and none have failed, you have probably gotten your money's worth out of them. Personally, I'd be worried that tire failure and possible Airstream damage are in your immediate future, most likely before the end of next season.

Also, you state that with "a straight edge across the tires, the depth of the outer treads is noticeably lower than the depth of the inner treads." Could you please post a photo of this, including the straight edge for reference?

I suspect that the tire tread may be distorted like some other photos we have seen in other posts. A few are extreme and look kind of like a bicycle or motorcycle tire, with shoulders that appear rounded. If that's the case, it sounds like the belts may be separating from the tire body.

Now, might be the time to look at Michelin XL or LT alternatives, depending on which best fits your application.

==========

GYM
0-1 = 3
1-2 = 10
2-3 = 14
3-4 = 25
4-5 = 7
5-6 = 6
6-7 = 5
7+ = 1

==========

Link to Tire Failure Poll: http://www.airforums.com/forums/f438...l-76867-3.html

[CapriRacer]

2 thoughts:

1) Wear on trailer tires is almost a non-issue. Conventional wisdom is saying that trailer tires should be replaced every 5 years. By that time, trailer tires usually don't have enough wear to worry about.

2) Using a straight edge is NOT the way to measure wear - or even evenness of wear. The tread of a tire is curved when inflated - except where it is in contact with the ground - and then the footprint isn't evenly pressurized. Measuring that pressure distribution requires specialized equipment and its meaning is hotly debated.

I think you need to be concerned about wear RATE, not wear pattern.

[Protagonist]

Originally Posted by CapriRacer

I think you need to be concerned about wear RATE, not wear pattern.

Within reason. Wear pattern makes a difference if that wear is scalloped, not uniform around the entire circumference, since that's often an indication of an out-of-balance tire. Wear pattern also makes a difference if it's not symmetrical, i.e all on the outer edge or all on the inner edge, since that could indicate a bent axle.

[nickmeloy]

Originally Posted by CapriRacer

2 thoughts:

1) Wear on trailer tires is almost a non-issue. Conventional wisdom is saying that trailer tires should be replaced every 5 years. By that time, trailer tires usually don't have enough wear to worry about.

2) Using a straight edge is NOT the way to measure wear - or even evenness of wear. The tread of a tire is curved when inflated - except where it is in contact with the ground - and then the footprint isn't evenly pressurized. Measuring that pressure distribution requires specialized equipment and its meaning is hotly debated.

I think you need to be concerned about wear RATE, not wear pattern.

OK. Help me on this issue.

All four tires look very similar with respect to the amount of wear and the wear pattern. The wear on all four tires is greater on the edges, but not bald by any means. The edges are worn to the extent that I do not feel comfortable in continuing to use the tires. Should I expect to get about 25,000 miles per set of tires in three years for the trailer I am pulling?

I cannot get pictures to post.

[cwf]

I would carefully drive to tire store and replace. Immediately

The next thing I would do is check the GAUGE I am using for air pressure. If the gauge is reading wrong you will be under inflated and that can an will cause the wear you show on that one tire.

Another cause may be you have your AS severely overloaded. Only the scales will tell the truth.

One possibility could be you are driving in severely rutted roads... But not likely.

[Silver Otter]

My (trusted) mechanic also mentions that turning on dual axle sets puts pressure on the outside edges which results in some extra wear there. As has been said above, even wear might be expected at 25,000; wavy or uneven wear is probably a bigger concern. We put a set of Maxxis M8008ST Load E on last year and have rolled along trouble-free for many miles out to Utah and back to Virginia, at 80 lbs.

[CapriRacer]

another 2 thoughts:

1) You shouldn't expect the tread surface of a tire to be flat. It should be curved. Using a straight edge is NOT the way to measure this type of wear. The right way is to use a tread depth gauge in the grooves.

A bit of a wrinkle is that new tread depths aren't always the same across the face of the tread. They might vary as much as 2/32nds - normally not, but it is still possible. You should expect some differences when the are worn - and the problem here is that unless you know how much the tread depths were new, it's hard to judge if they are wearing abnormally or not. A difference of 2/32nds would be cause for alarm. (See the problem?)

2) It is possible that your tires have developed a separation and it is causing a bulge in the center of the tread. It would be highly unusual for all 4 tires to separate at the same time. Usually there will be a single tire, perhaps 2, but not all 4.


If you feel uncomfortable, take the trailer to a tire dealer.

And posting pictures? Import them to an image hosting site such as Photobucket. Save the URL address, then click on the "Insert Image" icon above the reply box using the same URL. Please note: You can NOT insert the photo directly from your computer. It has to be available on the internet somewhere - and a hosting site is the best way to do this.

[Bbelk]

While people have tires on their minds. I just bought a 2010 27FB Classic with less then 100 miles on it. I have put another 150 on it. The tires look fine. Is there anything about not rolling a tire for 3 years that would do it damage that I should worry about?

While I was shopping for this thing I saw the results of a blow-out on the same model trailer with the same tires. It was not pretty.

[CapriRacer]

I would look very carefully for cracks. Not operating tires prevents the migration of the Antioxidants (AO) to the surface to protect the tire from being attacked by oxygen. The cracks may not appear right away, but the reduced AO's means they will crack eventually.

Cracks are also an indicator of the state of the rubber inside the tire.

- BUT -

A certain amount of cracking is considered normal. Judging that takes some experience. If you find cracks, take photos and post them.