Calling all tire pressure geeks...

[etojeo]

Yesterday as I was preparing the Stream for an upcoming trip, I checked the tire pressure. I picked her up two weeks ago from the dealer, and as part of the orientation we specifically discussed tire pressure. The 2019 Flying Cloud 25 has it clearly embossed on the tires that "maximum load 80 PSI".
I would speculate I have approximately 600 pounds of stuff on the Stream, so hardly maximum cargo capacity. But I was surprised to find that all four tires were at 55 PSI - this was a reading taken in the total shade of the storage overhang.
Shall I inflate the PSI to 75, or run her at current 55?
Thanks!
Ed

[bbandeddie]

I run at 45psi all winter to Mexico and back to Ontario. Everything stays put and the sidewalls barely get warm. 55psi should do it. (27FB)

[lsbrodsky]

I disagree. If those are Load E tires you want to run them near 80. Are they LT tires? While you will see lots of debate on the forum about tire pressure for comfort, the pressure provides sidewall strength. Trailer tires do not turn like car tires and heavy loads are placed on the sidewalls when you turn, especially when backing...look at the skid marks on concrete after you have done a backing turn. I would never run a trailer tire intended for 80 at 55. Many here run somewhat lower than 80 for comfort, though.

Larry

[Night owls]

I've run mine at 80 psi no matter how much cargo on board and seems to be just fine. I personally wouldn't run them at 55.

[Bob662]

Ed,
You'll get opinions all over the place. At the end of the day, you won't get much more than that -- opinions. I suggest you go to the Goodyear tire pressure chart (or whatever brand of tires you're using) and follow the manufacturer's recommended inflation for the size tire and trailer weight.

The sidewall states the pressure for MAXIMUM load carrying. But if you're not carrying a maximum load, why run that pressure? Some will say that max. pressure gives the least sidewall flex. They're probably right, but at a lighter weight and lower pressure, isn't the tire strong enough? I suggest the answer is "yes," and the manufacturers' tire pressure charts seem to confirm that.

[Mollysdad]

I'm not a tire expert, but I'm pretty good with common sense.
I run mine a 65 psi.

[uraljohn]

Current rig. 2019 FC25 RBT. When we picked her up at the dealer the tires had 88 PSI in them. Good thing I checked them before driving away. I lowered to 65 PSI and have run them there since.

Best way to determine appropriate pressure is to weigh your rig to determine how much weight the trailer axles are supporting. Figure what each tire supports and inflate to the recommended PSI per inflation chart.

As to running Load Range E tires at less than the maximum cold pressure of 80 PSI, my tow vehicle, 2013 Ford E150 XLT van equipped with Load Range E tires (8600 GVW) the door sticker specifies 55 PSI for the front tires. The axle rating is 3700 LBS. So at 55 PSI those tires can support 1850 LBS each. I usually run the at 50 PSI as the front axle comes in at 3200 LBS fully loaded ready to travel.

Find your happy spot with regard to the PSI to run. A CAT Scale is your friend.

[drbrick]

Tire pressure depends on the load and type of tire ... if you are running GY Endurance go to their website and download their tire pressure guide - in accordance to GY we run Blue Streak at 65#. On Hwy at 100K they increase to 70# running at about 70F...we monitor with a TST.

[rollingusa]

I would follow the pressure your tire show. Everyone has different opinions on what they use but everyone lives in different climates. Pressure changes all the time with temp change. If you have LT tires that state 80 psi as the max and you want to be able to carry a full load use that pressure. Know that it will go up as your tires heat up and the tire company knows and has already compensated for this.

[Oldtrapper]

Tire pressure specifications are a “cold tire inflation pressure”. It should be measured prior to the trailer being towed, in the cool of morning before sunlight has warmed the tire. The AS/Michelin spec for LT tires is a cold tire inflation pressure of 80 psi. As the day warms up, a 10 F degree increase will increase the tire pressure by roughly 1 psi so unless you’re experiencing extreme temperature swings, you don’t need to compensate for ambient temperature increases. Michelin have done a study that is available online that shows the the rolling tire temperature increases quite rapidly if lower inflation temperatures are used. Lower inflation pressures will increase the risk of a tire failure.

The other thing is, running lower inflation pressures makes no change in the combined spring rate of the tires and suspension; the suspension is so soft it dominates the combined spring rate. Some people suggest that they get improved ride by lowering inflation pressures but this is not the case unless they are running dangerously low inflation pressures.

[Alphonse]

Ed, I suggest you do a search here to get some real advice from a couple of tire engineers. The user names you want to look for are CapriRacer and Tireman9. These gents know what they are talking about and their advice is worthwhile. You will find hundreds of posts on this topic by them in the spirit of trying to help people based on well founded insights and experience.

I am fairly certain that they will tell you at a minimum to inflate per the placarded requirements on the side of your trailer. In addition they will likely advise you to inflate to the capability of the tire if it is more capable than the placard requirements.

[mpsgolf]

Highly recommend you go with tire manufacturer’s recommendation which us that pressure should be proportional to load. Divide your AS GW by number of tires, give yourself a small bit of pad, and use the recommended cold pressure for that tire load.

I downloaded this GY Endurance load / pressure table from the manufacturer. Trust the engineers. Their specs are not random they're inherent to the design of the tire.

[mykytiukr]

Ok, I am not a tire engineer. Back in the day when radial tires were becoming popular there were numerous articles published on this and I read every one I came across, and still do. Nowadays there is a liability for everything so when a recommendation is given(for just about anything)it is well above what is actually necessary.
This is the way I have been inflating tires on my big trucks, trailers, bumper pull equipment trailers, smaller trucks, etc. for years: Let’s say the tire says “65 psi at 3000 lbs(max load)”. When said tire is supporting 3000 lbs and inflated to 65 psi it is properly inflated! Now let’s say you have four of these tires on your travel trailer and it weighs 5000 lbs at the axles when hooked up going down the road. Each tire is only supporting 1250 lbs! At 65 psi the tire is rigid, little tread contact and no sidewall flex at all!!! There is a formula for this somewhere but what I do is know what the tire looks like, as in squat and tread area contact, when loaded at 3000 lbs at 65 psi, then inflate or deflate the lightly loaded tire to “Proper Inflation”. Usually about 20 to 25 psi. More psi than this is probably not going to hurt the tire except when you run over something sharp(even a rock)and the tire does not flex then punctures. But it will shake and jar your trailer and all your stuff inside unnecessarily because the tire is not absorbing anything! As long as the sidewall is not flexing any or not much more than it would at 3000 lbs 65 psi, it will never overheat or a have premature failure. This is all what an old school tire engineer will tell you and, like I said, this is how I have been doing it for the last 40 years or so and will forever!!! Gonna get some debate on this! I always have!!!

[Castaway]

What does the sticker on the road side of AS say . I would go by that.

[wulfraat]

This has been discussed at length in the forum. Bottom line only you can make the decision on what is the appropriate tire pressure. Your lower bound is the recommended pressure in the GYE chart above ... your upper bound is 80psi.

Personally the chart says I can run at 40 psi for my rig based on actual tire load when hitched and on a car scale. 80 is for “maximum load”. I choose to split the difference thereabouts and run at 65. Considering going lower to help 55 to further smooth out the ride.

80 psi gives you a max load of 11,320lbs across 4 tires. My 30’ international only has 7,200 - 7,500 lbs load on the tires when hitched and rolling down the road... I could run at 80psi but just don’t need that much overhead. The ride is most definitely firmer / more shock is transmitted through the trailer at 80psi....

Airstream have to (must) print 80 (max) on the tire plate attached to the trailer for legal liability purposes, not because that’s what is recommended.

[DavidaPeter]

Appreciate all these thoughts. I, too, got the tire pressure chart from Goodyear as our max inflation per load is as y'all describe. But according to the chart, we would be running at 25-30 lbs as we only have 1500 lbs per tire -- and I can't bring myself to do that. My strategy has been to slowly let the tires go down some from the 75 I had them at prior to seeing the chart. I'll just keep watching.
How can this all be so confusing and subject to opinion rather than knowledge?

[Alumaholic]

As usual when this question is asked, there is the full range of good and bad information before the thread is complete.
Special thanks to the Member who provided the Goodyear Load/Inflation Information.
It confirms that 55 PSI is right for my 27FB.
Overinflation is not only bad for tires, it is really bad for Airstreams.

I pay very close attention to tire shape at recommended pressure just to double check.

There is literature out there with good illustrations what the cross-section of a properly inflated tire should look like under load.
Thanks for the chart!

[rintintin]

Originally Posted by Oldtrapper

Tire pressure specifications are a “cold tire inflation pressure”. It should be measured prior to the trailer being towed, in the cool of morning before sunlight has warmed the tire. The AS/Michelin spec for LT tires is a cold tire inflation pressure of 80 psi. As the day warms up, a 10 F degree increase will increase the tire pressure by roughly 1 psi so unless you’re experiencing extreme temperature swings, you don’t need to compensate for ambient temperature increases. Michelin have done a study that is available online that shows the the rolling tire temperature increases quite rapidly if lower inflation temperatures are used. Lower inflation pressures will increase the risk of a tire failure.

The other thing is, running lower inflation pressures makes no change in the combined spring rate of the tires and suspension; the suspension is so soft it dominates the combined spring rate. Some people suggest that they get improved ride by lowering inflation pressures but this is not the case unless they are running dangerously low inflation pressures.

Always inflate at the pressure listed on your tires. If you have the misfortune of being involved in a serious motor vehicle you definitely don’t want that to be an aggravating factor which could lead you to legal trouble

[OTRA15]

FYI there are many threads about tire pressure in the "Tires" forum:

http://www.airforums.com/forums/f438/

. . . and elsewhere throughout this site:

https://www.google.com/search?q=tire...=airforums.com

FYI/FWIW

[Mollysdad]

Originally Posted by drbrick

Tire pressure depends on the load and type of tire ... if you are running GY Endurance go to their website and download their tire pressure guide - in accordance to GY we run Blue Streak at 65#.

I downloaded the GY tire inflation guide.
It's the same as the guide for the GY Marathons!

I'd like to hear how you weighed the trailer and arrived at 65psi.
It's funny, I totally agree with you but I'm surprised you came up with that number by using the guide.

I'll use mine as a test case. I have a 26' twin axles.
Let's say I weigh it and it weighs 7000#.
Of that 7000#, 1000 is on the hitch, not the tires.
So I have 6000# distributed evenly on four tires.
That's 1500# per tire.
Now to the GY chart.
Looks like I should be inflating to 28psi.


*Thanks mpsgolf for the tire chart!