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Old 10-27-2013, 02:10 PM   #85
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I have been watching this thread with interest these last few weeks as we choose the EB tire upgrade option on the 28' Serenity we purchased new last year. The placard on the trailer says 80 psi like any other trailer with the same tire package. I was skeptical about that psi value as soon as I saw it.

Tires are designed to have a specific sized contact area with the road. Too big, and fuel economy suffers due to the increased rolling resistance, increase temperatures due to excessive sidewall flex, etc. If the contact patch is too small, then there is less tire in contact with the road.

Having ridden motorcycles since I was old enough, the one thing that is most important to a safe and fun ride (besides the skill level and attitude of the rider) is the tires having a proper contact area with the road. If the tire pressure it too low, the contact patch was too large and the motorcycle would feel sluggish and not maneuver properly. If the pressure was too high, then the contact patch was too small and the tires would slide in corners, spin on acceleration and worse, lock-up sooner while braking. My point is, this principle applies to all tires regardless of application.

With all that said, I view the load inflation chart not from the perspective of "max load" and "safety factor", but from one of if my trailer weighs 8000#, I will have 2000# per tire, in order to get the correct sized contact patch I need between 55 - 60 psi. My trailer regularly weighs in at 6400# on the trailer axles according to the scales while loaded for camping. I have adjusted my tire pressure to 50psi for a total of 7760#. Around a 20% margin of safety. As far as the differences in the driving characteristics, I noted a much smoother ride for the trailer (less stuff bounced out of place in the trailer) and a surprising increase in braking power from the trailer. I stop in shorter distances and the trailer brakes don't lock-up as often, especially when the brakes are cold, compared to 80 psi when the trailer was delivered. I haven't noticed any appreciable change in fuel economy. The trailer tire temperature is consistent with the Tundra's tires so I am not over heating the tires. No noticeable tread wear issues either.

Just throwing in an alternative thought process for those who are not sure what tire pressure works for them.
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Old 10-27-2013, 02:14 PM   #86
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Oh, to answer the OP's question, the dealer in Canada where we bought the trailer charged us $2100 for 5 16" tires and rims (4 EB rims, 1 black steel rim for the spare). It is obviously cheaper to do it on your own, but we didn't want the hassle of dealing with the old tires and rims.
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Old 10-27-2013, 06:34 PM   #87
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Question, Has anyone just traded their AS in for the Eddie Bauer model to get the wheel upgrade?.

I am holding at $1366 OTD w/o spare wheel/tire right now w/MS/2. Waiting for a deal on the spare w/wheel.
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Old 10-27-2013, 07:56 PM   #88
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These analogies on tire capacity and trailer weight do not take into consideration the weight of the trailer transferred to the truck in my case approximately 1000lbs.I do not need to nor will I inflate my LT's to max pressure of 80psi as there weight capacity at 80 psi would far exceed the weight capacity of my loaded Airstream.
I will not air my tires on my passenger vehicles to there max stated tire pressure as I could not stand to ride in them and they also do not need the additional weight capacity to handle the load required.
I do watch my TPMS and have experimented with different tire pressures and have found that from 65psi to 80psi the temp variance is negligible .I run 70psi as my target pressure
I personally do not the Airstream put much thought in their 80psi tire recommendation with the EB they just posted what was on the sidewall of the tire they choose.
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Old 10-27-2013, 09:00 PM   #89
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Moflash, your concern then is harsh ride for the Airstream. Mine too. But I see no indication that is the case; everything stays put, no drawers or doors open. I just installed new recliners in the front without any anchor. They do not move. I've got a good w.d. hitch (Propride w/1400# bars), and a 2012 1/2 ton Ram with coil front and rear springs. The hitch connection is soft.

I agree with setting truck tire pressure as needed for the load and it's definitely noticeable in the ride, but the trailer seems to do well with the Airstream-recommended 80 psi.
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Old 10-27-2013, 09:10 PM   #90
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I've got a question. With the concern of some out there that 80 psi is too much and will beat the trailer up with a rough ride, what do you think the all steel RIB tire from Michelin will do? It's for sure a tougher tire and a summer only tire, not to be used in freezing conditions. Why? Does it get stiff as a board when cold? An awful lot of quotes here about using them on our Airstreams. Is that really a good idea? Should we know more about their restrictions first. Anyone? Please post.
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Old 10-27-2013, 09:20 PM   #91
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My 28 rides better at 70psi along with my Airsafe hitch it is just that there is no reason to run your LT's over inflated for no reason and hard. on your trailer.There is a difference in ride quality.as experiment just add another 10 psi to your pickup tires and drive your normal route for a day.
Your trailer is even lighter than mine?
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Old 10-27-2013, 09:46 PM   #92
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Could it be the Michelin 16" LT tires at 80 psi are no stiffer than the original GYM ST tires at 65 psi, as I understand ST tires have stiffer sidewalls?

As I have said earlier, there is no noticeable difference in the condition of the trailer and it's contents since we changed to the Michelin LTs.
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Old 10-27-2013, 10:02 PM   #93
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Moflash , Stoker, I've run the Marathons from 55 to 65 psi and the new Maxxis 8008s from 70 to 80 on the 30 flying cloud. I can see no difference in the trailer after running a rough or smooth road with the different inflation pressures. Yes, I can feel a very small difference in the 2500 Chevy Duramax itself between 65 and 80 psi, but not enough to matter. Tire wear seems to be unaffected between those pressure ranges also. Sure, the lighter the trailer, the more a harsh ride will result from highly inflated tires. I would think you at least inflate an "E" tire to match or higher than your axles GW. Also, the lower you run your tires ,the less reserve capability one tire has when the tandem wheel picks up a nail. Do you know of any study that shows max pressure on LT or trailer tires can be damaging to the vehicle? I only know of trouble caused by under inflation..
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Old 10-27-2013, 10:49 PM   #94
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It is fairly obvious that under inflation can be a bigger problem than over inflation. What I'm saying is I am not under inflating my tires. They are properly inflated for the load I am carrying. Just like in a car that weighs less than the carrying capacity of the tires, the car manufacturer has lowered the pressure on the tires in relation to the weight of the vehicle to provide the best profile area of the tire to the road. Soft enough for proper contact patch to provide enough grip for handling and braking properly, and firm enough to support the weight with what we hope includes a safety margin.

To carry the GVW of my trailer, 7600#, inflating my tires to 50 psi gives me a carrying capacity of 7760#. We have yet to put enough stuff in our trailer to hit the GVWR, and approx. 1000# of the trailer ends up on the TV. The actual weight my trailer axles are subjected to is generally 6400#, give or take a bit of water in the tanks. So, in reality, I am only loading up my tires to 80-85% of the load rating at 50 psi. If I was to inflate to 80 psi, I would only be loading to 60% of the load rating. I would expect the profile of the tire to the road to be incorrect. A very round, hard tire that creates a unnecessarily small contact area with the road minimizing the effectiveness of the tires to keep the trailer from skidding under evasive maneuvers or hard braking. I agree that depending on the road, the ride of the trailer might not change enough to bounce the soap out of the holder, but giving up valuable contact with the road seems counter-intuitive to me. Again, my experience stems from motorcycling where it is more noticeable when you loose traction. You tend to fall down.

As far as picking up a nail in a tire and losing its ability to carry the load, the other three tires take up the slack for the brief period of time until the rig gets stopped. Just like a car when it gets a flat. I haven't down the math, but I would guess that a properly loaded car with properly inflated tires would overload the remaining tires should one go flat. Flats happen all of the time, things seem to be working okay there. Some will say that the trailer is different as the tires are immediately adjacent to each other and one tire will take more load than the other remaining two. Yes, just like it does when crossing a steep driveway or some difficult campsite entries. At least the flat tire is still carrying some weight, not much, but some.
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Old 10-27-2013, 11:35 PM   #95
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Stoker, I wonder if lower pressure would improve road contact and braking. Just a quick "google" gave a test some years ago that indicates it's more about the road surface type, and whether wet or dry, than tire pressure. Lower or higher pressure were not consistent in stopping distance.

http://www.nhtsa.gov/cars/rules/ruli...ure/LTPW3.html

That's not enough evidence to prove much of anything, maybe there's better, more recent testing. But I wouldn't lower tire pressure below Airstream recommendation for that reason.
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Old 10-28-2013, 02:20 AM   #96
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"16" Inch Wheels" is here on post mainly because many wanted to get to a quality road tire of "E" rating on our trailers and replace those Goodyear Marathon "D" tires that have a reputation for way too many failures. You either go with the very few choices of 15 in trailer tires with a 10 ply, E rating or go up to 16 inch where you can get a quality 10 ply tire that is also higher speed rated. With money as no object, 16 inch rims and tires is the way to go.

Why do so many Marathons fail? Is it just that Goodyear makes flawed products? Is it that the Marathon 8 ply tire is just too close to its max weight capability, with the bigger trailers especially if the psi is allowed to get a little low? Maybe..

The point here is to do all we can to avoid tire failure. It was never a concern about tread wear, Or how soft a ride we can set up for the trailer. I just don't want to have to replace aluminum side panels and dump valve fittings. So I buy a quality 10 ply, E load rated tire, air it up to the "E" load psi or at least near there and drive on. If ride quality, wear, braking ability (maybe) is of greatest concern, the need to go expensive 16 inch wheels is not there.
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Old 10-28-2013, 05:47 AM   #97
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Quote:
Originally Posted by dkottum View Post
Hmmmm, who do I believe about tire pressure on my Michelin 16's?.

Airstream factory and Service Center recommends 80 psi. A tire engineer recommends less.....
When I read this, I wondered if dkottum meant me.

Then I re-read what I wrote and came across these passages:

Quote:
Originally Posted by CapriRacer View Post
.........I think you'll find that tires commonly are specified at 85% of the load table value........and I recommend 85%.
I see where that would be confusing.

What I am trying to say is that the tire should be specified such that is it run at 85% of its rate capacity as determined by the tire size/inflation pressure combination found in the tire load tables.

Put another way, you want to over-specify the tire by 15%.

That might mean going to a higher load range and using a higher inflation pressure - OR - it might mean going to a larger sized tire (one with more load carrying capacity)

What I do NOT mean is a blanket recommendation of running the tire lower than the maximum pressure.

And lastly, if a vehicle manufacturer specifies MORE than a 15% overcapacity, I would go with that as well.

This means the one needs to know what the vehicle weighs - wheel position by wheel position.

I hope that clarifies things.
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Old 10-28-2013, 09:31 AM   #98
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Capri, I think you are saying if Airstream recommends 80 psi, go with that.

But then, why do I need to know what the vehicle weighs - wheel position by wheel position? Because in reality, that's not going to happen. This is a travel trailer with varied loading and water/waste transfer each trip.
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