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dkottum · 10-10-2014, 09:40 AM

No problem Rich. Last weighing was 6 months ago, we live at a lake in Minnesota and seldom travel in summer. Winter is our time to use the Airstream and it gathers "stuff" as we go about, gets completely unloaded each season. Am careful with weights in the trailer, and where placed.

SteveH · 10-10-2014, 09:57 AM

Our manufacturer's stated gross is actually 11,500, and when you add 15% to that, 13,225. The good news is when you figure six tires, it's not but 2200 lbs which is less than a 31 ft Classic. I do worry about tires on both vehicles because our gross can easily reach 19K with full tanks.

Phoenix · 10-10-2014, 01:26 PM

The Airstream factory, Discount Tire and others recommend running trailer tires at maximum pressure printed on the sidewall.

We run 80 psi in the Michelin XPS Ribs (225/65x16, LR-E) on our 2005 19' Bambi (4,400 lbs, single axle).

20,000 miles, so far; and absolutely no problems.

AnnArborBob · 10-10-2014, 01:30 PM

Quote:

Originally Posted by dkottum

Thanks Bob, 6700# was trailer weight hitched and weight distribution applied. We were really loaded after a winter's shopping by one of the world's great bargain hunters including H F Coors' nice heavy dinnerware/serving sets for family, and full water.

Steve, that load put us at or a little above GVW of the trailer if we add approximate hitch weight back in.

Wow! That was a heavy load! A bit over maximum as you indicated. I wondered about that when I saw the posted weight. Glad you made it home safely!

Ag&Au · 10-10-2014, 03:40 PM

Quote:

Originally Posted by Phoenix

The Airstream factory, Discount Tire and others recommend running trailer tires at maximum pressure printed on the sidewall.

We run 80 psi in the Michelin XPS Ribs (225/65x16, LR-E) on our 2005 19' Bambi (4,400 lbs, single axle).

20,000 miles, so far; and absolutely no problems.

Is there any downside to using maximum pressure other than faster wear in the center of the tire compared to the sides of the tread?

I always use max pressure (80 PSI) for the same reason. ( I've been told to by the dealer who installed the tires) Unless I have an error in my logic, the maximum pressure is going to equate to minimum sidewall flex and thus minimum temperature rise. If I have to replace the tires a bit earlier, I will exchange that for peace of mind.

Ken

AnnArborBob · 10-10-2014, 04:07 PM

Quote:

Originally Posted by Ag&Au

Is there any downside to using maximum pressure other than faster wear in the center of the tire compared to the sides of the tread?

I always use max pressure (80 PSI) for the same reason. ( I've been told to by the dealer who installed the tires) Unless I have an error in my logic, the maximum pressure is going to equate to minimum sidewall flex and thus minimum temperature rise. If I have to replace the tires a bit earlier, I will exchange that for peace of mind.

Ken

It is perfectly safe to operate the tires at their maximum inflated pressure. You will probably not notice any difference in tire longevity since you are likely to need to replace the tires well before you use up the tread under either case.

The advantage of running the tires at maximum pressure is basically never having to worry about under-inflation due to trailer weight (you still need to make sure that your trailer is not overloaded or unevenly loaded, however.)

The disadvantage of running the tires at maximum pressure is a rougher ride for your trailer with the possibility of damage to the trailer.

TG Twinkie · 10-10-2014, 05:26 PM

I run 55# in the ST tires on my 26' Argosy. 25,000 miles from Canada to the Mexican Border in every state, north, south and west of Nebraska. Elevations from -250ft to 10,800ft in elevation.
Not a single problem in all those miles. Knock on wood.

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dkottum · 10-10-2014, 10:33 PM

Quote:

Originally Posted by AnnArborBob

Wow! That was a heavy load! A bit over maximum as you indicated. I wondered about that when I saw the posted weight. Glad you made it home safely!

In a hurry readying to go this morning, took another look at weight ticket, it was 6520# rather than 6700# so were under GVW rating of 7400#. We are much lighter this trip until she goes shopping.

Towed 260 miles at 65 PSI in 16" Michelins on smooth Minnesota I-94 to my son's farm. Rock solid stability as always with ProPride hitch, no hint of trailer sway, no semi's pushing us around, no trailer tire sway at 65 PSI. The trailer connection felt less rigid on the few bumps we went over.

Looking for some nasty roadways and wild sidewinds when we leave on Monday another check.

dbj216 · 10-17-2014, 05:35 AM

I run 65 psi in my six new 16" LT load range E tires. I weigh 7800 lbs hitched and I am below the max load capacity for these E rated tires. I picked 65 psi interested in a softer ride trying to keep the old Airstream together on rough roads. I'm guilty of towing pretty rigid with my F-350 and Propride. Although I don't have much shifting in the Airstream after a long day's towing.

We traveled 3900 miles in September on mostly two lane state highways with no problems noted.

I wish I had a "g load" meter for the Airstream while towing. I wonder how much of an "earthquake" really goes on back there. I was down to 40 mph on some of those old, rough New England roads.

I note the Ford F-350 recommends 65 psi for front 18" load range E tires, 80 psi rear. So I think running 65 psi is not a problem for the tires.

I am concerned about side loads in sharp turns with my triple axle trailer. But even at 65 psi I figure I have a lot of capacity in the tires. The 15" ST load range C at 50 psi had significantly less capability. I understand there is a lot of force applied to the axle spindles in sharp U turns on pavement. I leave pretty good rubber marks dragging that thing around corners. Uff Da

Doug, enjoy your Airstream travels. We'll keep you posted on the temps and snow depths this winter in Battle Lake!

David

switz · 10-18-2014, 01:26 AM

When not towing, the 2012 2500HD Cummins Dodge manual suggested 45 psi on the rear tires (LT265/70R17E) versus the 70 psi towing (happens to exactly equal axle rating load). I run the rears at 80 (maximum side wall rating). The lower pressure makes the ride more pleasant for full figured ladies....

One might check their owners manual to see if there is lower pressure mentioned for non-towing driving.

The next trip out I will try 72 to 73 psi on the trailer and compare results to the 75 psi. The 75 psi number raised pressure to 82 on a warm day but temps were 20 degrees or so higher. 80 psi generated higher psi numbers and temperatures for us.

CapriRacer · 10-18-2014, 06:23 AM

First, I think the question should what pressure do you run AFTER you made an upgrade. The size of the wheel and the brand are irrelevant.

So I think you need to use the loads on the tires (or estimates) and do the math. Allow me to do one:

Your vehicle starts off with ST225/75R15 Load Range D. You don't know the loads on the tires, but haven't experienced any tire failures, but are uncomfortable with the situation and decide to increase the tire size to LT225/75R16 Load Range E and a well know brand of tire.

The load carrying capacity of an ST225/75R15 Load Range D is 2540# at 65 psi.

You decide you want a 15% increase in load carrying capacity to cover the side to side and front to rear load variation and another 10% to provide a "margin of safety": 3213#

To carry that load, an LT225/75R16 Load Range E needs to be inflated to ........ opps! The maximum load carrying capacity is 2680# - only a 6% increase!

- BUT -

You did go from a speed restricted tire (65 mph), to a speed rated tire (say, R = 106 mph), so you need to figure out how to deal with that.

Well, you can increase the speed restriction of an ST tire, by using more inflation pressure and reducing the load. Doing the math, you will find that at the same 65 psi, the aforementioned ST tire at 85 mph can carry only 2032#, so the change in tire would result in more than a 32% increase. Since you were shooting for a 25% increase, that seems like a good number.

To verify that things are working correctly, you do a pressure build up test: You measure the inflation pressure first thing in the morning and then after more than an hour of towing at highway speeds (you like to use 65 mph, plus or minus), you find the build up to be 6%. Since that is below 10%, you conclude that this pressure is good.

dkottum · 10-18-2014, 08:11 AM

All things considered, I have settled on verifying things are working correctly by noticing the tires aren't overheated or blown out traveling from Battle Lake, MN to Memphis, TN using 65 psi in our 16" Michelins.

We'll hit the road again in a few days. Navy Blue Angels perform here this weekend at the airfield.

dbj216 · 10-18-2014, 11:01 AM

CapriRacer knows tires! I appreciate your input in these Forums. I think the less than 10% pressure increase after at least an hour of running is a good test for selecting tire pressures that also support the loads.

I was passed by an old pick up pulling an old utility trailer full of stuff. I noticed the trailer tires looked soft. Sure enough, as he pulled back into the right lane going 70, that trailer tire vaporized in a cloud of smoke. You are right Doug, no blow outs means you are doing something right!

I never thought the Mercury Capri as a good Racer. I'll bet you race something else if you are into that sort of thing. I enjoy watching and reading about vintage sports car racing. But CapriRacer seems like an oxymoron.

Woops, shouldn't change the subject.

David

dkottum · 10-18-2014, 11:30 AM

David, CapriRacer does know tires. I do get weary of all the conflicting advice in these tire threads so I just settled on something reasonable (anywhere from 50-80 psi has been suggested), hit the road at 65 psi, and keep an eye on them.

I think they are a smoother ride for the Airstream at 65 psi than the factory recommended 80 psi, judging from towing at both pressures and how it feels from the driver's seat. There is absolutely no difference felt in stability but then we are using a Hensley/ProPride style hitch so absolute stability is normal.

CapriRacer · 10-19-2014, 06:18 AM

Quote:

Originally Posted by dbj216

CapriRacer knows tires! I appreciate your input in these Forums......

My pleasure.

Quote:

Originally Posted by dbj216

..........I never thought the Mercury Capri as a good Racer. I'll bet you race something else if you are into that sort of thing. I enjoy watching and reading about vintage sports car racing. But CapriRacer seems like an oxymoron.......

I updated my avatar to show a highly cropped photo of my Capri racing at Roebling Road in Savannah, GA. That was in 2001. Shortly after that photo the engine blew up and it hasn't been to the track since.

Actually, Capri's made great race cars. They are simple and straight forward. They have a Pinto engine for which there were a ton of go fast parts.

The car is now sitting in my garage, and since I am now retired, it is time to get the beast (critter?, varmint?) running again.

dbj216 · 10-19-2014, 11:21 AM

Well I'll be! I think yours is the first one I've seen. I've been going to Road America for 20 years to watch the "Historic Races" the third weekend in July. I enjoy watching the vintage Alfas, Porches and Lotus screaming into turn 5. Vintage sports car racing makes vintage Airstreams look cheap!

Thanks for the explanation of your user name.

David

PS I hijacked this thread, didn't I?

mefly2 · 10-20-2014, 11:58 AM

With our Michelin 16s on the Eddie Bauer, we run 68 psi when loaded with full water, propane, and personal gear. If we add ~350# for a bike, we raise the tire pressure to 72 psi. In either case, I note that at 60 mph sustained driving on the freeway roads that the pressure increase has not exceeded 5 psi hot. No signs of sway at either pressure setting.

I am more concerned about the temperature differential between the edge of the tread and the center of the tread; sometimes, there is 10 degree F more in the center ... it seems like that would indicate that I need more pressure in order to reduce the flex in the center of the tread ???

Hlamberton · 10-20-2014, 01:24 PM

My 2012 21'Bambi recommends 65# for my 16" wheels. Weight of loaded trailer is 4500#. Just replaced them at 19,500 miles with edges worn out. I would say the 65# recommendation is too low.

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dkottum · 10-20-2014, 02:28 PM

Quote:

Originally Posted by Hlamberton

My 2012 21'Bambi recommends 65# for my 16" wheels. Weight of loaded trailer is 4500#. Just replaced them at 19,500 miles with edges worn out. I would say the 65# recommendation is too low.

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How did you get 16" wheels on your Bambi and where specifically did the 65 psi recommendation come from?

Your single axle Bambi at 4500# puts on more load per tire than my 6520# tandem axle Flying Cloud so 65 psi with 16" tires may be low for your particular Airstream.

Tireman9 · 10-20-2014, 02:36 PM

Quote:

Originally Posted by dkottum

Travel trailer tires at max sidewall pressure. Is there a reference to support that?

Yes. I have a post on the solid technical reason behind advising that multi axle trailers should use the inflation on the tire sidewall associated with the max load. Nov 20 2013 Its called "Inter-Ply Shear"

Also one on what you need to do to switch from ST to LT tires June 23 2014