Another Tire Question

[Thomas G.]

Originally Posted by baron100

..... A failure of either tire could result in a catastrophic accident. Replacing a tire at the side of the road by itself presents significant risk to the owner while changing the tire. Think I-405 in Seattle at rush hour.

The single most important safety decision we make as trailer owners is in tire selection. The travel and boat trailer forums are replete with pictures of mangled tires and damage to trailers from tire failures. Often owners report multiple failures.

In a recent Casita event, an owner experienced loss of trailer and tow vehicle and thankfully was able to get her daughter and granddaughter to safety in time. Another owner reported multiple thousand of dollars repair due to a tire failure. It is disconcerting to me that this trend seems to continue even though a solution to many of these failures has been identified for years.

"In approximately three years, roughly one-third of the tire's strength is gone."

Fact is, the trailer manufacturers have scrimped on the original tires they provide their customers. Yes, the tires they provide may marginally support their trailers on paper when they come out of their factories. The many failure encountered, often after minimal miles, is suggestive that they are not adequate. This seems to be even more noticeable for those that operate their trailers in a high heat environment like Arizona and Texas in the summer time.

While I agree with you that keeping good tires on your trailer is important. I think your post is a little over the top in the fear mongering department.

[Francesca Knowles]

Originally Posted by baron100

Given, the above, I believe that Jon has right sized in his choice of tires and in fact will not be purchasing more tire than he needs.

I was told by many that I had over killed my selection of Maxxis M8008 ST225/75/15 tires for my Casita. I run them at 80 psi, so they run cooler and can handle the maximum loads the trailer experiences when traveling down the road.

I replaced the first set at 32,000 miles with new ones and they looked almost identical to the old ones. No cupping or irregular wear as I was warned. If they "bounced" down the road as I was warned, it was not evident to a fellow traveler that followed me for 5,000 miles.

45,000 miles on Maxxis "E" rated tires from Canada to Mexico without a failure.

I maxed up "I believe", because just about everything the conclusion is based on is a matter of belief, not of fact.

Leaving aside for the moment the inaccuracies contained in the whole post, I'd like to simply point out that the O.P. himself can make a similar claim of longevity for his C-rated tires, which according to you were deliberately undersized by the trailer maker who placed cost above customer safety.

Jon himself reports NO "failures" in 37,000 miles of travel on these "underrated tires"- the only concern in that department has to do with the fact that although they performed fine well beyond normal expectations/predictions for trailer tire life, there's a disturbingly evident wear pattern.

That pattern is clearly indicative of a problem unrelated to the tire itself, and certainly would be just as evident on any tire, no matter how "thick".

I'm glad you feel good about your choice to put enormously overrated tires on your trailer, but to imply as I think your post does that anyone who doesn't do the same is endangering Life, Limb, and Trailer is simply untrue, not to mention unhelpful.

It is, in short, more evangelism than anything else, as I think I opined in the first line of this post.

Keep the Faith!

Francesca

[Jon Vermilye]

Well, actually, 33,000 miles...

As to the original tires, again they were well within the trailer's weight. According to Goodyear's Marathon Trailer Tire inflation tables, at 50 PSI the tire rating is 1820 lbs, or 3640 lbs for the axle, well over the axle rating & even further over the typical axle weight of an Escape 17B (mine is 2800 lbs loaded).

The Maxxis table shows the same values for the 205/75/15 tire. I have no problem going with the "C" rated tire, however they are difficult to find in that size. As I noted before, I will probably be purchasing the "D" rated tire & run it at the appropriate pressure for my rims.

The unusual wear I mentioned in my original post is not all that visible in the pictures - the outside edge wear is down beyond the tread on the section of the tire opposite the wheel weights but fairly even across the tire 180°s around the tire. In any case, I suspect there is enough outside wear that I will have the alignment checked, providing I can find someone who knows how to do it.

[rabbit]

Originally Posted by Brian B-P

The unnecessarily higher-rated tire is heavier, probably more expensive, less compliant (and therefore has less traction), and may build more sidewall heat due to resistance to flexing.

Got no dog in the overspec fight but I could not help but notice this statement. Brian, is it really the case that a stiff sidewall can generate and retain greater heat than a more flexible sidewall? This seems to me to run counter to the universal experience of flexing everything from muscles to steel. It seems to me that elastic deformation [bend/stretch] creates heat at the molecular level and that the greater the deformation (stretch and bend) the greater the amount of heat created. You seem to be saying that resistance to deformation creates heat. I think that must be what's happening right now in my cranium

jack

[Francesca Knowles]

According to my understanding, yours is the correct assessment, Jack...flexing creates heat, and flabbier tires flex more.

But an overspec'd tire isn't going to flex any less than an adequately spec'd tire that's properly inflated for the load.


Francesca

[Steve L.]

Originally Posted by rabbit

Got no dog in the overspec fight but I could not help but notice this statement. Brian, is it really the case that a stiff sidewall can generate and retain greater heat than a more flexible sidewall? This seems to me to run counter to the universal experience of flexing everything from muscles to steel. It seems to me that elastic deformation [bend/stretch] creates heat at the molecular level and that the greater the deformation (stretch and bend) the greater the amount of heat created. You seem to be saying that resistance to deformation creates heat. I think that must be what's happening right now in my cranium

jack

The answer, of course, is "it depends!"

I'm making generalizations here, but the tire deflects in two ways. Primarily in the "hoop" direction from round to flat in the contact are and then round again. The other way is in the sidewall.

Within a subset of tires, ST's for example there is generally little difference in the deflected radius acheivable with changes in sidewall reinforcement. (heavy with the generalizations here since you CAN change the deflection with certain reinforcements)

So, if you have basically the same deflection, the thicker, stiffer tire will run hotter. The load formulas were basically designed such that all similar tires, all ST tires say, have the same percent deflection at their rated load and inflation. A given size "C" tire at 50 psi carrys the same load as the same size "D" tire at 50 psi. They will both have about the same deflection at the same rated load and pressure and thus, If the "D" tire has more "stuff" in the sidewall it will have more losses (exhibited by heat and/or rolling resistance). Heat in and of itself is not bad...Too much is.

Like everything about a tire, there's a a bazillion variables that effect the tire. Generalizations are just that and a passive-agressive can pick out exceptions. I don't know if I've even added to the discussion. These tire discussions are largely doomed anyhow.

[rabbit]

Yep, that clears it up. Steve, we "passive-aggressives" prefer to think of our activity as a sort of cavalry probe at a point of potential weakness in the line of argument. Often the weakness is in our heads. I have to run away now.

jack

[Steve L.]

I wasn't thinking of you when I wrote the passive aggressive comment. Yours was a good question/comment and one I've fielded from my bosses in the past so I've sorted through it before.

[Francesca Knowles]

Well, if you're saying that there's anything passive about my aggression, I double-dog dare you to come over here and say that!

Francesca

[Carol H]

Originally Posted by rabbit

Yep, that clears it up. Steve, we "passive-aggressives" prefer to think of our activity as a sort of cavalry probe at a point of potential weakness in the line of argument. Often the weakness is in our heads. I have to run away now.
jack

Please dont! I love reading your prose!

[Carol H]

Originally Posted by Steve L.

These tire discussions are largely doomed anyhow.

Tires tend to fall into the same realm as discussions on safe towing practises, wax or floor polish, generators or solar, using Sway Bars, best type of tow vehicle and fresh to the list this week using Weight Distribution Hitches.

[cpaharley2008]

and the list goes on...

[cpaharley2008]

HHHmmm,
I wonder if all these discussions are contributing to the climate issue we are experiencing, last year being the warmest on record.

[rabbit]

Thanks Carol. I'll tell the infinite monkeys to keep up the good work.

[Brian B-P]

Steve provided the same answer that I would to Jack's (reasonable) question about stiffer sidewalls running hotter, although he stated it perhaps more eloquently and certainly more authoritatively than I would have. Thanks, Steve.

Originally Posted by baron100

Most of us have single axle trailers. A failure of either tire could result in a catastrophic accident. Replacing a tire at the side of the road by itself presents significant risk to the owner while changing the tire. Think I-405 in Seattle at rush hour.

The single most important safety decision we make as trailer owners is in tire selection. The travel and boat trailer forums are replete with pictures of mangled tires and damage to trailers from tire failures. Often owners report multiple failures.

...
Buy the best tire you can put on your trailer...

All of this logic applies equally well to the front tires of the tug - you don't want one of those to fail! Does anyone use the very best tire sold for their tug, and do they choose tires with much higher rated capacity than the axle rating, and much higher even than the manufacturer's original equipment?

Even if someone does want to use the "best" tire, this is not the same as the tire with the highest rated load capacity.

If trailer tire failures are routinely caused by under inflation and overloading, as is commonly asserted in this forum and by tire manufacturers and retailers, then the solution is obviously to use the right size of tire, properly inflated... just as we do on our tugs.

Originally Posted by baron100

An extra two plies of tire construction affords him additional protection in the form of reduced risk of tire penetration from a foreign object (a leading cause of failure after under inflation) and is a tire of much greater strength.

Ply ratings do not describe the actual number of plies of tire reinforcement. They are scheme invented many years ago to relate the now antiquated non-belted bias ply tires (think 1930's) to standard load ranges: the "ply rating" indicated that the tire had capacity similar to a traditional tire with that many layers of fabric in the carcass.

For instance:
2-ply rating (typical max inflation pressure 24 psi) = Load Range A
4-ply rating (typical max inflation pressure 35 psi) = Load Range B (= passenger car Standard Load or SL)
6-ply rating (typical max inflation pressure 50 psi) = Load Range C (= passenger car Extra Load or XL)
8-ply rating (typical max inflation pressure 65 psi) = Load Range D
10-ply rating (typical max inflation pressure 80 psi) = Load Range E

In practice, modern tires have many fewer plies, especially in the sidewall. Standard Load car tires typically have a single sidewall ply, I have had Extra Load tires with 2-ply sidewalls, and my motorhome's stock Michelin XRV 235/80R22.5 Load Range G tires have one-ply sidewalls, albeit one layer of thick steel cord (small tires commonly have polyester sidewall plies). Even the tread doesn't have the number of belt layers under it that were once used.

A LR-D trailer tire does not have two more plies than LR-C, and may not have any more plies... but read the sidewall if you're curious.

Applications which require greater sidewall damage resistance (such as off-road truck designs) routinely add more protective rubber, rather than more reinforcing cord layers. That might be handy for incompetent trailer pullers, who bounce the trailer tires off a lot of curbs.

Originally Posted by baron100

Consider one other point. Many trailer manufactures scrimp on the axles they chose. A loaded Casita SD (and many other brands) trailer is very close to the max 3,500 lb rating the Dexter axle provides, leaving minimal margin. It is reasonable to assume that the additive tension resulting from the axles stressed to the maximum causes additional stress on the tires.

I don't understand the term "additive tension". If this is meant to refer to higher shock loads due to suspension bottoming, then it makes sense that additional tire load capacity is needed... but are these trailers really routinely hammering the compression travel limit?

[Alf S.]

Originally Posted by Jon Vermilye

Well, actually, 33,000 miles...

As to the original tires, again they were well within the trailer's weight. According to Goodyear's Marathon Trailer Tire inflation tables, at 50 PSI the tire rating is 1820 lbs, or 3640 lbs for the axle, well over the axle rating & even further over the typical axle weight of an Escape 17B (mine is 2800 lbs loaded).

The Maxxis table shows the same values for the 205/75/15 tire. I have no problem going with the "C" rated tire, however they are difficult to find in that size. As I noted before, I will probably be purchasing the "D" rated tire & run it at the appropriate pressure for my rims.

The unusual wear I mentioned in my original post is not all that visible in the pictures - the outside edge wear is down beyond the tread on the section of the tire opposite the wheel weights but fairly even across the tire 180°s around the tire. In any case, I suspect there is enough outside wear that I will have the alignment checked, providing I can find someone who knows how to do it.

Hi: Jon Vermilye...I still remember being shocked at having my 69 Dodge Van aligned. It took 2 guys to do it. One to hold the long iron bar against the axle and the other guy to swing the sledge hammer.
Alf S. North shore of Lake Erie

[Andrew Gibbens]

Originally Posted by Carol H

Tires tend to fall into the same realm as discussions on safe towing practises, wax or floor polish, generators or solar, using Sway Bars, best type of tow vehicle and fresh to the list this week using Weight Distribution Hitches.

But you leave out religion and politics? Shome mishtake shurely?

[Carol H]

Originally Posted by Andrew Gibbens

But you leave out religion and politics? Shome mishtake shurely?

You seem to have forgotten Andrew those are two items we are not permitted to mention at all here!