WHY 16 inch rims & tires?

[SteveSueMac]

Originally Posted by BoldAdventure

I know it wasn't very friendly.



It's that weight per tire that made me nervous. And the fact weight shifts around. We know two other full-time families on the road with 27's running those tires. It would just make me nervous. That's cutting it really close.



I use the printed Michelin load tables to inflate our Airstream-based on my cat scale weight.

Yup.

Hey - you may want to check with our resident "tire guys" - seems I recall their recommendation was to always go to full tire PSI - I can't recall if that was ST only or all tires used on trailers including LT. If you're adjusting by weight table you're probably under 80 psi but might want to change that (unless I'm wrong which happens from time to time &#128530

[xrvr]

Originally Posted by switz

As I mentioned earlier, the axles on our 2014 Classic are carrying 8,062 pounds when loaded for camping.

The individual tire loads are:

Curb front: 2,042 pounds
Curb rear: 2,062 pounds
Street front: 2,034 pounds
Street rear: 1,921 pounds

Thus three of our four tires would exceed the allowable derated weight capacity of 1,985 pounds for the 15" Michelins.

Oddly enough, the 34' Classics with three axles and six tires would work with the 15" Michelins.

Looks like the new replacement for the Michelin would work? The defender?

[DoublTrouble]

Follow up question, por favor, you don't really subtract tongue weight do you?

[RLS]

With all the discussions on load amount, can anyone tell me what the max. load a tire that is derated to 1,985 lbs. will sustain? Will it bear the weight of say 3,200 lbs.? or will it just pop! Just wandering

[BoldAdventure]

Originally Posted by RLS

With all the discussions on load amount, can anyone tell me what the max. load a tire that is derated to 1,985 lbs. will sustain? Will it bear the weight of say 3,200 lbs.? or will it just pop! Just wandering

Well that tire with the weight evenly distributed between it and another equal tire on an axle rated for that, will support upto 3970lbs.

That tire all by itself, with all the weight on it ........ not so much.

[Siegmann]

Well, I'm not a tire engineer, but as I understand it, the key to load ratings is the dynamic force exerted on the tire. As when you go over a bump at 65 mph. In such a case the load on the tire could be 2-3 times the static load. So you could probably put 4,000-6,000 lbs on that single tire sitting in your driveway without it failing. Even Airstream indicates you can drive for 50 miles at a reduced speed with a flat on a two axle rig. That doubles the normal load on the remaining tire. Same as when people service a tire/wheel when they drive a tire up onto a ramp on a two axle rig and leave it there all day. But none of this is relevant to when you're driving down the highway.

[mykytiukr]

Mr. boldadventure. 2 years and 1953 posts! You must know it all!!!!!

[smead42]

Michelin does not recommend their tires for trailer use, will not warrant them... even if they are installed at the AS factory.

[switz]

Perhaps the poster of #48 might find this Michelin document of interest.

Both CostCo and Discount Tire gave me warranty on both the 15" and 16" Michelin tires mounted on my Airstreams.

When crossing the scales, the number recorded for the trailer axles is the weight the tires are carrying. The hitch participation with weight distribution engaged is in that number. It is possible to vary the number on the trailer axle weight by adjusting the hitch or shifting stuff inside the trailer, but the trailer axle(s) and tires are only supporting the weight shown on the scale ticket at that moment in time.

In some models of Airstreams the axle ratings equal the GVW of the trailer. Our 25FB had two 3,800 pound rated axles which could support 7,600 pounds with a 7,300 pound GVW. The same axles are used for the 26/27/28 models with a GVW of 7,600 pounds but the 27FB Eddie Bauer has a GVW of 7,800 pounds. So the tongue obviously is carrying the 200 pound difference. The single axle 19' model has a 4,300 pound axle rating and a GVW of 4,500 pounds. These axle ratings and GVW numbers are from the appropriate Airstream literature and parts manuals.

I have Michelin LT265/70R17E tires that came on the pickup. Dodge suggests 45 psi for the rear tires (a 2,255 pound tire load or 4,510 pounds for both tires) when the bed is totally unloaded to soften the ride on the stock suspension truck. The front axle is rated 5,500 pounds and the door label suggests 60 psi for the front tires. The load table for that tire shows that at 60 psi it will carry 2,760 pounds or 5,520 pounds for two tires. The rear axle is rated 6,010 pounds and the tire table suggests 70 psi for a load capacity of 3,005 pounds or 6,010 pounds for two tires. I typically run all the truck tires at 80 psi when towing.

The Michelin LT225/75R16/E LTX M/S2 tires mounted on our Classic with a GVW of 10,000 pounds (with two 5,000 pounds rated axles) are rated 2,680 pounds at 80 psi. The load versus pressures numbers from the Michelin tire manual are:

80psi 2,680 (E)
75psi 2,560
70psi 2,440
65psi 2,335 (D)
60psi 2,190
55psi 2,060
50psi 1,940 (C)
45psi 1,790

Since I know my individual tire loads and the heaviest is 2,062 pounds camping ready, I could run 56 psi per the chart. I run 75 psi and the temperature rise and pressure rise are where they should be. Many are using 72 psi which would mean about 2,500 pound load support or a 20% safety margin Using 75 psi I have about a 25% safety margin.

Lacking the individual wheel weights, the prudent RVer would have to take the total axle scaled weight and add at least a 20% safety margin. So in our case with a 8,160 pound axle load, the target safety number is close to 9,800 pounds which could be carried at 73 psi. A 25% safety margin number is about 10,200 pounds (exceeds the two 5,000 pound axle load of 10,000 pounds) at a pressure of 75 psi.

There are tire experts here on Airforums that suggest the 80 psi number to strengthen the tire sidewalls for better support in turns where the sidewall stresses are much higher.

[xrvr]

Great info, thanks. Clears a few things up.

[CapriRacer]

Originally Posted by RLS

With all the discussions on load amount, can anyone tell me what the max. load a tire that is derated to 1,985 lbs. will sustain? Will it bear the weight of say 3,200 lbs.? or will it just pop! Just wandering

The load carrying capacity of a tire is a function of many things. Among them are the volume of the air chamber (which is where "size" comes in), inflation pressure, speed, road roughness, and suspension (as in soft suspensions are easier on tires than hard or no suspension).

A RADIAL tire with a load rating of 1985# at standard highway speeds can sustain a STATIC load of 165% of the load carrying capacity at 65 mph - or 3275#. But move that vehicle even slowly, and that value changes.

And lastly, the way a RADIAL tire would fail if it was over loaded would be for the belt edges to develop a separation, leading to a bulge, eventually leading to the top belt detaching from the rest of the casing. Whether the tire continues to hold air is a function of the strength of the body plies. In a static mode, the tire would still fail in the same way - belt edge separation, leading to belt detachment.

HOWEVER, this is not to say that an OLD, but overloaded, tire would fail in ONLY this way. Age makes the rubber weak and a slightly different failure mode is possible. Whether the tire would continue to hold air during the failure varies from tire to tire and also depends on the situation.

[tjdonahoe]

Originally Posted by smead42

Michelin does not recommend their tires for trailer use, will not warrant them... even if they are installed at the AS factory.

Costco mounted and balanced my 16 " wheels for my airstream, with the warranty papers, Hello !

[RLS]

I want to thank those that answered my question. I have been trying to decide if an "E" rated 15" LT tire was needed for safety when or if there is a blowout or if the 15" Michelins would be enough. I tend to run on the heavy side with the trailer and my axle weight hooked up with weight transfer engaged coming up to about 6,600 to 6,700 lbs. That 165% margin sounds good, so maybe the Michelins would be the way to go. I would rather use the Michelins due to the softer ride from only needing 50 lbs. air pressure compared to the "E" rated ones needing 85 lbs.

Thanks, Bob

[dames7]

Look at where your tires are made, Goodyear are made in CHINA, enough said.

[BoldAdventure]

Like Switz and tjdonahoe Costco mounted, balanced and gave me warranty papers on mine too. I documented this in my "Help me order my 16 inch Rims" thread. Including the costs I paid at Costco.

[smead42]

Perhaps the poster of #49 should talk to Michelin NA headquarters in Greenville SC and see what they say about their tires on a travel trailer and what they say about AS mounting them at the factory.

[BoldAdventure]

Originally Posted by smead42

Perhaps the poster of #49 should talk to Michelin NA headquarters in Greenville SC and see what they say about their tires on a travel trailer and what they say about AS mounting them at the factory.

One wonders if my Costco warranty just means if I bring it into Costco they'll replace it, but if I try a claim with Michelin they'll deny it. Seems like a legitimate question.

[dkottum]

The least of our concern is the warranty on our Airstream's 16" Michelins. In the highly unlikely event they will fail, the most we can lose it the price of a new tire minus pro-rating.

We gain a highly reliable tire, as opposed to the original warranted GYM's which may take out the wheel well metal with it in the likely event it will fail.

[switz]

CanAm recommended we run 44 psi in the Michelin LTX (P) 235/75R15 XL tires we mounted on our 2013 25FB International Serenity. The axles saw 5,860 pounds camping ready as compared to the derated capacity of the four tires being 7,940 pounds. That is about a 30% safety margin.

Note that our 25FB and several others had about 200 pounds more weight on the curb side rear tire than the other three that caused more tire wear in that location.

We are also running the recommended 44 psi in the same Michelin LTX (P) 235/75R15 XL tires installed on the 2015 23D International Serenity that has a 6,000 pound GVW versus the 7,300 pound GVW of the 25FB. We plan the first outing in early December and will check the scales with all the "stuff" aboard. The safety margin should be much higher on the 23D.

[CapriRacer]

Originally Posted by smead42

Perhaps the poster of #49 should talk to Michelin NA headquarters in Greenville SC and see what they say about their tires on a travel trailer and what they say about AS mounting them at the factory.

You have to be very careful HOW you ask the question concerning using LT tires on a trailer.

If you ask about replacing ST tires with LT tires, you are likely to get a negative response, but if you ask if LT can be used on a travel trailer, you're likely to get a positive response.