WHY 16 inch rims & tires?

[Mrjkq]

I see a lot of talks about doing this change out, ok, why spend many $$$ on new rims & why Michelin tires? I've always presumed that Goodyear made a good tire and what's the advantage of doing this?

[SteveSueMac]

http://www.airforums.com/forums/f465...ml#post1267426

This thread can help explain. Good luck!

[AnnArborBob]

The current thinking is that light truck tires (LT) are safer than pure trailer tires (TT.) Indeed Airstream is putting LT tires on it's larger and more expensive new trailers.

There are a lot more LT choices with 16 inch rims than there are with 15 inch rims. But if you look, you can find LT tires for 15 inch rims. Michelin makes a quality LT tire (so does Goodyear, but a lot of folks have had a bad experience with Goodyear Marathons which are a TT and not a LT tire) so that's why a lot of people who are making the switch are going for 16 inch rims and Michelin LT tires. You could get the same security with 15 inch LT tires from a quality manufacturer.

Having said all of the above, there are some people who swear by their 15 inch Goodyear Marathons and will report going millions of miles without any incidents whatsoever. But there is no doubt among those who are open to factual, engineering based information that LT tires are better made than are TT tires. I know of lots of people who have switched from TT to LT tires. I know of no one who went from LT to TT tires.

[Wingeezer]

Because, depending on the size/weight of your trailer, if you want to switch from
ST (special trailer) tires to LT (light truck tires) which at the moment seem less likely to suffer blowouts and possible expensive trailer damage, you may have to go to a 16" size in order to get a tire with adequate load rating - this is my understanding anyway.

I have had 16" Michelins on our 30' Classic now for a few years and am very happy with them so far.

Others are quite content with their 15" Goodyear Marathon ST tires.

It's just a personal decision, take your choice!


Brian.

[xrvr]

What about the 15 inch michelins?

[BoldAdventure]

I did it for the bling bling! Word Up! Shake n bake!

Also, I don't want to die. Mostly that.

[Wingeezer]

Originally Posted by avionstream

What about the 15 inch michelins?

Could be just fine if they are ok for the GVW of your trailer - I don't think they are for mine (10,000# GVW.)

If I am wrong, I wasted my $$ buying new wheels and larger tires!

In fact, when I spoke on the phone to someone at CanAm he did recommend
15" Michelins for my 2005 Classic 30

I chose not to go that route after looking at the Michelin website for allowable load levels for the different sizes.

Could be I made a mistake, and if I did, I would be interested to hear, although I have the large 16" wheels and tires now anyway, so i suppose it would be only of academic interest!


Brian.

[BoldAdventure]

The 15 inch Michelin's where fine for the GVW rating of my Airstream. I have two friends running them. But on the forums here I read a number of folks talking about 15% safety margin, and when I calculated that number, the only option was the 16 inch tire. The 15 inch was cutting it close to the 7500 GVW.

Granted though, my Airstream across the cat scale weighted 6984lbs last time we weighted her. Fully loaded for full timing.

[nrgtrakr]

Maybe there is something wrong with our 75 Overlander. It had 7.00x15s on it when we got it, and there was evidence of the tires rubbing the lead edge of the wheel well. So when we replaced the museum piece tires we went smaller and now there is plenty of room.
I can't imagine it with 16" wheels.

[dkottum]

We travel widely about the country and the most likely failure item to take us off the road was the original GYM tires. We wanted reliability, minimize failures to put us alongside the interstate or backcountry road with little or no shoulder, especially at night.

The 16" Michelins have a stellar record on Airstreams. The Airstream factory installs them on some premium models, or offer them as an option. So we made the change costing us $1,000 for new 16" Sendel wheels and Michelin tires, after selling the originals and keeping the unlikely-to-ever-need original spare.

We also decided TPMS has limited value with the Michelins, and may not prevent damage in the unlikely event of a sudden blowout, so do not use them. A few hundred more dollars saved. Not a recommendation, just how we do it.

[SteveSueMac]

Originally Posted by avionstream

What about the 15 inch michelins?

Working for me. You have to derate them 10% so you get 1984# load capacity per tire. My 27FB Flying Cloud comes in at 6000# on the scales loaded for camping (it gained 200# this year which can creep up easily!). So even derated, I still have almost a ton of extra load capacity on them.

I keep them at their full 50 PSI pressure and have an internally mounted TPMS. Even in the hottest days, pressure never rises above 10% and temps don't rise more than 30* above ambient.

[Mrjkq]

My AS is about 6500 lbs (guestimate) as I roll down the road, I usually drive at 65 MPH at full tire inflation of 65 lbs so my concern is how safe is this when driving in normal weather conditions, or even in very hot conditions, my Marathons have preformed well for the 3000+ miles I've driven so far. I'm rationalizing that new tires on a new AS should provide a few years of service &when the time comes then switch to 15 inch Michelin LT provided I can find them. What's wrong with that theory?

[SteveSueMac]

Mrjkq - I think the actual tire engineers on these forums might suggest that the Marathons fully inflated at 65 PSI, 3 years old or less, not overloaded and not driven over 65 MPH should be just fine. Many folks have had no problems with them. Some folks have horror stories with them. They have much more load capacity than 15" Michelins - 2540 per tire vs 1984 per tire. That's more than an additional ton of load capacity for a double axle trailer. Worth thinking about.

You could do either and be fine. Is say the only thing "wrong" in your question is guessing at the weight. You really only know when on the scales. Take a trip over the scales fully loaded for camping to be sure.

[Al and Missy]

I may be mistaken, but the 15" Michelin tires are technically not LT (Light Truck) tires. Their nomenclature starts with P225, meaning they are a passenger car tire. Michelin rates them for light truck use but they must be de-rated 10% for that service. I went with 16" Michelin LT tires because at 75 psi they had slightly more load carrying capacity than the 15" ST tires on my trailer (which had substantial margin against the 6300# GVW of my trailer).

There are arguments that state that the ST tires are designed to survive the torsional stress imposed on the tires of a tandem wheel trailer. I think the nearly 100% margin I have at 75 psi should be sufficient. Only time will tell.

Al

[sgschwend]

I checked out the difference in tire weight and found a big difference. That was enough to show me the difference.

[SSquared]

Originally Posted by avionstream

What about the 15 inch michelins?

Some people have been using the 15 inch Michelin model LTX MS/2 P235/75-15 108T XL. It is rated for 2183 pounds.

This tire has been around for a number of years. Michelin is replacing the LTX MS/2 with a new tire called Defender LTX M/S. The 15 inch Defender LTX is once again a passenger type tire, not an LT tire, but its load rating is higher. The tire designation is 235/75-15 109T with a load rating of 2271 pounds.

[xrvr]

Good info on the new tires. Thanks.

[SteveSueMac]

So derated those Defenders would carry 2064# per tire.

[xrvr]

And that would be enough for my Avion and probably some larger AS.

[switz]

When I did the 15" stock GYM ST225/75R15D tire swap to 15" Michelin LTX (P) 235/75R15 XL tires on our 2013 25FB International Serenity, the Michelin sidewalls had a rating of 2,183 pounds.

Per the federal regulation below:

49 CFR 571.110
Tire selection and rims and motor home/recreation vehicle trailer load carrying capacity information for motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less.

S4.2.2.1
Except as provided in S4.2.2.2, the sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle's certification label required by 49 CFR part 567. If the certification label shows more than one GAWR for the axle system, the sum shall be not less than the GAWR corresponding to the size designation of the tires fitted to the axle.

S4.2.2.2
When passenger car tires are installed on an MPV, truck, bus, or trailer, each tire's load rating is reduced by dividing it by 1.10 before determining, under S4.2.2.1, the sum of the maximum load ratings of the tires fitted to an axle.

S4.2.2.3
(a) For vehicles, except trailers with no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.
(b) For vehicles, except trailers with no designated seating positions, equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.


We derated the operational load capacity to 1,985 pounds or 7,940 pounds for four of them. Our loaded for camping trailer axle load was 5,860 pounds with a total trailer weight of about 6,935 pounds of it's 7,300 pound GVW rating.

The 7,940 load rating was inadequate for our Classic when loaded for camping as the Classic exceeds that number on the axles when camping ready. Thus we installed the 16" Michelin LT225/75R16/E LTX M/S2 tires on 16" SenDel T03-66655T wheels.

The 27/28 models have a 7,600 pound rating which is easily within the capabilities of these tires. The 27FB Eddie Bauer model has a 7,800 pound GVW and would start crowding the safety margin for the 15" Michelins. However, the factory offered the 16" Michelin LT225/75R16/E LTX M/S2 tires mounted on SenDel T03-66655T wheels as an option for that model and made them standard on 2015 and later Classics. The 16" tire and wheel combination just mentioned is for sale at Jackson Center for most recent 25" and longer Airstreams and on display just after you pass through the doors of the service center.

I replaced the stock 14" GYM ST215/75R14C tires with the 15" Michelin LTX (P) 235/75R15 XL tires mounted on SenDel T03056545T wheels on the 2015 23D International Serenity for a better load capacity and reliability. That 15" combination will also raise the trailer to the same elevation as the 25FB was since we are using the same Mercedes to tow the 23D that we used for the 25FB.