Tires - Page 9 - Fiberglass RV


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Old 05-12-2013, 07:04 PM   #113
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Originally Posted by Francesca Knowles View Post
I thought you'd be interested to read that despite its business decision not to make trailer tires for smaller vehicles, Michelin does indeed subscribe to the notion that trailer tires are different in function and design.
That's not news to me - I mentioned it back in post #73, and in various previous discussions.

The optimization for a specific service is mostly about maximizing tread life. Since tread life is irrelevant to most recreational users, this optimization is of little value to us. Similarly, while Michelin builds specific drive and steer axle tires for commercial truck use, their model for motorhomes (the XRV) is an all-position tire: it is more like an all-season to the non-RV's straight summer tire, because traction matters more than tread life on a motorhome that will likely rot of old age before accumulating the hundred thousand of kilometers it would take to wear out.

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Originally Posted by Francesca Knowles View Post
You'll find their brief description of a trailer tire's form/function at this link. It's remarkably similar to Carlisle's, by the way...
There is a similarity in that both describe the optimization of tires for trailer service, although Carlisle says "a free-rolling trailer tire isnít called on to turn, swerve and grab the pavement like a steer or drive tire" (apparently Carlisle-equipped trailers are guided around corners by some unseen hand from above), while Michelin says "trailer tires must withstand strong lateral and braking forces".

On the more controversial points that routinely arise in this forum, Carlisle and Michelin do not appear to agree:
Use of non-trailer-specific tires
While Carlisle's published statements have been interpreted here to mean that anything but an ST tire is inappropriate, in the sizes for which Michelin offers trailer-specific tires (only big commercial stuff), they also offer all-position tires (yes, the same tire on a steer axle, a drive axle, and a trailer axle).
Inflation pressure
While Carlisle apparently advises owners to always inflate to the sidewall maximum, Michelin says this in the Michelin X One Air Pressure Maintenance Practices (and example, the only document I noticed with inflation pressure right in the title):
Quote:
Cold inflation pressure should be based on maximum axle load in daily operation
... followed by the usual load/inflation table. This is the same document, and the same advice, for both drive and trailer service (for which they have different optimized versions). It does not at any point suggest running tires at their maximum inflation pressure regardless of load, and does not direct air pressure to be handled any differently for trailer tires than for drive tires (this particular model is not typically used in steer applications because it is so wide).
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Old 05-12-2013, 09:12 PM   #114
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Hmmm. Dare I ask if the prescription of prestigious and respected Michelin holds any water--er--I mean air? I do.

jack
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Old 05-12-2013, 10:06 PM   #115
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Quote:
Originally Posted by Brian B-P View Post
That's not news to me - I mentioned it back in post #73, and in various previous discussions.

The optimization for a specific service is mostly about maximizing tread life. Since tread life is irrelevant to most recreational users, this optimization is of little value to us. Similarly, while Michelin builds specific drive and steer axle tires for commercial truck use, their model for motorhomes (the XRV) is an all-position tire: it is more like an all-season to the non-RV's straight summer tire, because traction matters more than tread life on a motorhome that will likely rot of old age before accumulating the hundred thousand of kilometers it would take to wear out.


There is a similarity in that both describe the optimization of tires for trailer service, although Carlisle says "a free-rolling trailer tire isnít called on to turn, swerve and grab the pavement like a steer or drive tire" (apparently Carlisle-equipped trailers are guided around corners by some unseen hand from above), while Michelin says "trailer tires must withstand strong lateral and braking forces".

On the more controversial points that routinely arise in this forum, Carlisle and Michelin do not appear to agree:
Use of non-trailer-specific tires
While Carlisle's published statements have been interpreted here to mean that anything but an ST tire is inappropriate, in the sizes for which Michelin offers trailer-specific tires (only big commercial stuff), they also offer all-position tires (yes, the same tire on a steer axle, a drive axle, and a trailer axle).
Inflation pressure
While Carlisle apparently advises owners to always inflate to the sidewall maximum, Michelin says this in the Michelin X One Air Pressure Maintenance Practices (and example, the only document I noticed with inflation pressure right in the title):

... followed by the usual load/inflation table. This is the same document, and the same advice, for both drive and trailer service (for which they have different optimized versions). It does not at any point suggest running tires at their maximum inflation pressure regardless of load, and does not direct air pressure to be handled any differently for trailer tires than for drive tires (this particular model is not typically used in steer applications because it is so wide).
Yes sir... Just as soon as I can figure how to cram a 445mm+ wide 22.5" tire into the wheel wells of my 13 Scamp I guess I would follow that particular Michelin chart!
They do warn that those are minimum pressures, but I could maybe run those tires with no air at all since the chart starts at 14000#. Now to find me some hoops to fit 'em up with a 5 on 4.5 bolt pattern!
Right now I can't even install 14s, so there's likely gonna be some needed mods But at nearly 4ft tall they're gonna look great on my Scamp and they're only a grand apiece!
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Old 05-12-2013, 10:43 PM   #116
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Thanks Floyd. Smelled the bait in the last parentheses.

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Old 05-14-2013, 12:37 AM   #117
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I assume that both Floyd and Jack are bright enough to understand that the Michelin examples are large because they don't sell small trailer tires, and that the principles are the same in any size. I do appreciate the bit of humour. My parenthetical comment was about being wide compared to other heavy truck tires.

The point about pressure is that Michelin says explicitly to adjust pressure to suit load - obviously to at least the minimum - which clearly means not at the tire's maximum regardless of load.
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Old 05-14-2013, 12:44 AM   #118
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Originally Posted by floyd View Post
Yes sir... Just as soon as I can figure how to cram a 445mm+ wide 22.5" tire into the wheel wells of my 13 Scamp I guess I would follow that particular Michelin chart!
Just one tire in a big well in the middle, facilitating a walk-around bed configuration, but unfortunately requiring the use of a special hitch to keep it from leaning over (custom built by Can-Am RV, of course).
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Old 05-14-2013, 02:19 AM   #119
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Back in the late 50's my dad bought a new Ford T bird. The car handled poorly and followed grooves in the freeway. The oem tires were probably Firestone bias plys and were so lumpy and worn out at 10.000 miles that my dad wanted to trade the car in for something else. He went up to Sears to get new tires before selling the vehicle. The tire salesman told him to try some Michelin X's, that were working really well on big heavy American cars. So they installed a set. No white sidewalls, only black. When inflated to the recommended pressure they appeared under-inflated. I remember my dad coming home and raving how the T Bird was a whole different animal. It drove smooth and quiet virtually transforming the car into something pleasurable to drive. Needless to say he kept the car! After about 50,000 miles the tires were looking about half worn, so he popped on another set. The ones he took off were worn evenly with no cupping or anything like the Firestone bias tires. Michelin was so far ahead back then it was a no brainer to keep buying them over the American options. They do know how to make tires. Radials by design seem to be laterally soft which may not be desirable for a trailer. Michelin is a radial tire company primarily, so may not want to build small trailer tires. The big truck michelins are often a lot wider than conventional tires which may provide some lateral stiffness. They take the place of duals in some cases. Most of the concrete trucks around here use them.
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Old 05-14-2013, 08:51 AM   #120
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Originally Posted by Brian B-P View Post
I assume that both Floyd and Jack are bright enough to understand that the Michelin examples are large because they don't sell small trailer tires, and that the principles are the same in any size. I do appreciate the bit of humour. My parenthetical comment was about being wide compared to other heavy truck tires.

The point about pressure is that Michelin says explicitly to adjust pressure to suit load - obviously to at least the minimum - which clearly means not at the tire's maximum regardless of load.
Nope, just not bright enough to equate semi-trailer tires with Scamp tires. Too many years as a fleet mechanic have driven the differences home. Heck, I'm so dumb that I see differences in P metrics among different profiles, brands, and compounds.
Besides even in the chart cited,they do warn that those are minimum pressures for the load. Anything below that on a road truck is a threat to other driver's safety. Pressures above the chart and below the maximum...not so much.
BTW,Am I to assume that Michelin wants you to decrease pressures at the unloading dock and increase them again at the loading dock? Doesn't happen... Fleet tires are set at least to the maximum expected load plus a margin up to the maximum sidewall pressure.
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Old 05-14-2013, 12:27 PM   #121
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Did you guys really miss the point of Michelin's description of correct design for (any size) tires on axles other than drive/steer, or are you just pulling my leg? I ask because that leg gets pretty numb after awhile, so it's hard to know...

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Old 05-16-2013, 02:25 PM   #122
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BTW,Am I to assume that Michelin wants you to decrease pressures at the unloading dock and increase them again at the loading dock?
As anyone who read the referenced material knows, the answer is no. Neither does your car or pickup truck manufacturer suggest changing the tire pressure every time a passenger gets out or in.

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... Fleet tires are set at least to the maximum expected load plus a margin up to the maximum sidewall pressure.
Right... not simply to the sidewall maximum. Again, just like your car or pickup truck, for which the manufacturer directs the use of a pressure sufficient and appropriate for that vehicle, allowing for operation at its maximum load... not the tire sidewall maximum unless the vehicle's allowed axle load requires that much pressure.
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Old 05-16-2013, 02:29 PM   #123
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Originally Posted by Francesca Knowles View Post
Did you guys really miss the point of Michelin's description of correct design for (any size) tires on axles other than drive/steer...
Nope, didn't miss that, any more than I missed the need for my minivan to have different designs of tires on the driving and steering front than on the non-driving and non-steering rear.
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Old 05-16-2013, 02:37 PM   #124
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Heck, I'm so dumb that I see differences in P metrics among different profiles, brands, and compounds.
So, do you assume that, since there are these differences, that a car must use only the brand and model of tire that it has from the factory? My guess is "no".
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Old 05-16-2013, 02:44 PM   #125
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Originally Posted by ruscal View Post
Radials by design seem to be laterally soft which may not be desirable for a trailer.
...
The big truck michelins are often a lot wider than conventional tires which may provide some lateral stiffness. They take the place of duals in some cases. Most of the concrete trucks around here use them.
Most commercial truck tires are still the traditional tall-and-skinny proportions; they are used singly on steer axles and in dual pairs on drive and trailer axles, are of radial construction, and have no lateral stability issues. The classic common size for the biggest highway trucks is 11R24.5, which has the proportions of a common ST tire... just almost twice as large in every dimension. When I stop in traffic beside a big truck I often look at the tire size - I can't remember the last time I saw a bias-ply tire on either truck or trailer (brands other than Michelin are also radial).

There are some wide (low profile, e.g. 65-series) tires usually called "super singles") that are mostly used on steer axles and castered pusher and tag axles for higher capacity; they are very common on the front axles of dump trucks and those concrete mixer trucks. Less commonly, there are very wide (very low profile, e.g. 50 series) commercial tire sizes now available (usually called "wide base" tires) to replace a conventional dual pair with a single tire; they are on drive and trailer axles. Radial construction may have made these tires more practical, but is certainly not restricted to them.
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Old 06-09-2013, 07:04 PM   #126
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There. Tired of arguing with you guys and gals. Ha ! ....put that on your little fiberglass trailers....see if you can hurt this one......

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