Safe Tire Pressure

[Morgan guy]

I have a 2007 AS Classic 27'. It has a GVWR of 9000 lbs. I havve 4 Maxxis load range E tires rated at a capacity of 2830 lbs/ 80 Psi, for a total load of 11,320 lbs. With an excess capacity of 2,320 lbs, I would like to run a lower air pressure than 80 lbs to give a softer ride to the trailer. Does anyone know how the pressure adjustment affects the load capacity, in other words, what can I safely lower the pressure. The label on the trailer says 65 lbs but doesn't reference what load range of tire.

[bryanl]

check the tire temperature with an IR thermometer when you stop for breaks. If the tires run hot (> 140F), they need air. If they run cool (< 120F) you might get away with reducing air pressure somewhat.

The question being why you are running tires rated for much larger loads than needed while, at the same time, trying to find best ride. These two issues don't complement each other but rather contradict.

65 psi is typical D load range max sidewall rated PSI, 45 is C load range. 80 is typical for E load range.

[A W Warn]

I do not know about your wheels, but my wheels have a 65 psi max air pressure.

[Inland RV Center, In]

Originally Posted by Morgan guy

I have a 2007 AS Classic 27'. It has a GVWR of 9000 lbs. I havve 4 Maxxis load range E tires rated at a capacity of 2830 lbs/ 80 Psi, for a total load of 11,320 lbs. With an excess capacity of 2,320 lbs, I would like to run a lower air pressure than 80 lbs to give a softer ride to the trailer. Does anyone know how the pressure adjustment affects the load capacity, in other words, what can I safely lower the pressure. The label on the trailer says 65 lbs but doesn't reference what load range of tire.

More than likely, when you drop the tire pressure enough so you don't beat the trailer to death, the tires will show abnormal wear.

Also, most wheels won't take 80 PSI, over a long haul, without a fracture showing up.

"D" tires provide all the safety and performance that's needed, AND, with room to spare.

Andy

[overlander63]

Check the tire placard on your trailer. The recommended pressure should be listed there. Generally, it is 60-65 psi. Some smaller Airstreams with smaller/lower load range tires will be less.

[markdoane]

Here's the chart you asked for.

[kds]

Originally Posted by Inland RV Center, In

More than likely, when you drop the tire pressure enough so you don't beat the trailer to death, the tires will show abnormal wear.

Also, most wheels won't take 80 PSI, over a long haul, without a fracture showing up.

"D" tires provide all the safety and performance that's needed, AND, with room to spare.

Andy

So are there any disadvantages to buying a load E tire? I have 4 year old GM on my trailer now and will be replacing this month. My GW is 7600 and my tire guy advised me to go to a an E rated tire. Any idea why he would recommend this? I thought it would just be for extra safety. He recommended Greenball tires.

Kelly

[mojo]

Inflation

• Always inflate trailer tires to the maximum inflation indicated on the sidewall.
• Check inflation when the tires are cool and have not been exposed to the sun.
• If the tires are hot to the touch from operation, add three psi to the max inflation.
• Underinflation is the number one cause of trailer tire failure.

Load Carrying Capacity

• All tires must be identical in size for the tires to properly manage the weight of the trailer.
• The combined capacity of the tires must equal or exceed the Gross Vehicle Weight (GVW) of the axle.
• The combined capacity of all of the tires should exceed the loaded trailer weight by 20 percent.
• If the actual weight is not available, use the trailer GVW. If a tire fails on a tandem axle trailer, you should replace both tires on that side. The remaining tire is likely to have been subjected to excessive loading.
• If the tires are replaced with tires of larger diameter, the tongue height may need to be adjusted to maintain proper weight distribution.

[Phoenix]

Just a comment, but the tire temperatures mentioned above may be inaccurate, depending on your location. In Arizona, the "cool" running temperature of 120-degrees or less doesn't apply year-round; as in the summer, tires can measure this or higher when standing in the sun, even before your Airstream hits the street.

We verify 80 psi in trailer tires in the evening or early morning before leaving on trips, then don't worry about specific tire temperatures on the road. I have an infrared thermometer and check the tires at fuel and rest stops, but that is more to verify that they are still approximately the same temperature in comparison to the reading at the previous stop, rather than to verify a specific temperature range.

The Airstream tires usually measure approximately the same temperature as the tires on our tow vehicle, although the rear tires on our pickup are usually 5-10 degrees hotter because they are the drive wheels and we usually have a lot of stuff in the bed.

Note: We run load range E tires at 80 psi, because our single axle Bambi has a higher tire load (i.e., more weight per tire) than larger models with multiple axles.

[Ray Eklund]

Mojo. I am with you... aren't I?

I was blessed with the AS wheel size of 14" and 50 pounds maximum. The four factory Goodyears fell apart the first year. Punctures through the tread, blowouts. When I brought the 23 footer home I noticed bubbles in the outside smooth surface. The friendly Goodyear dealer said I must have done something to them and stiffed me good for a replacement. Good bye Goodyear.

I bought 5 TowMax Power King 14 inch tires. ALWAYS inflate them to the maximum of 50 pounds. I do not drive any differently... NEVER had a problem since. My solution to the 14 inch C rated tire and 14" wheels is getting 15 inch wheels and D rated tires. I will probably AVOID trailer rated tires and use a Michelin street tire. As some has said in some older thread... you will die and be sued for using non trailer tires on your AS. I think they have it wrong. I will die and kill others USING trailer rated tires. I will wait until there is some rating tests done to fix the problem with trailer rated tires.

Inflate your tires and your AS will pop its rivets??? Inflate your tires and your AS will fall apart and be a parts trailer. The screws in the cabinets will fall out of your AS once you drive off of the dealer's lot. Drawers coming off their hinges. Plumbing coming loose. Must be tire pressure related? Now that I have "upgraded" my hinges and hardware I have virtually nothing falling off.

I had trusted the judgment of some professionals on the Forum, but now have had to try out my own ideas. Things have improved for my back country uses for trailer and tow vehicle since I started using common sense.

My Tundra 2008 came with Goodrich, C rated mud and snow tires and a street Michelin spare on a steel wheel. They did not last with tire punctures through the tread and excessive wearing. I bought five of the Michelin E rated tires from Costco, Nitrogen used for "air", inflated to 48psi when mounted at Costco. I have not needed to add Nitrogen since I bought the tire set. They have never given me one problem. My Tundra is at 63,000 miles and has not shaken apart, exploded on the highway or had another tire problem. They are tough to balance, because there is tire rubber on these tires. They are also a bit expensive to swallow... but you will not regret it.

This dialogue I have not edited or prewritten with all of the fine details, miles driven and when tire failures occurred. Why do you think Toyota and AS put the tires on their products... because they are the best or they are cheap and will do, getting you off the lot.

We spend months traveling the back roads. Gravel, rock, dirt, mud, snow, slop and anything in between. I drive like the guy who is flying you on the Jumbo Jet to Australia. I want my truck, my AS, my tires, my water filter, AS faucets replaced with something that is good, etc. Never killed anyone. Never hit a Moose on a mountain road. Never had the aluminum pop off the frame and kill a baby chipmunk on the side of the road. I am sure there are some who will criticize the messenger and I am use to that. My trailer and truck NEED to handle the loads and roads I use in the back country. My methods ARE REAL.

I am saying. Listen to the advice some of these people are giving to you and then think about it some more. Common sense may save your life.

My friend bought a 2012 Tundra. The Goodrich tires are the same as my 2006's. He was told NOT to inflate the tires to the max when towing as it would ruin the suspension... What!? The commercials show them hauling a ton of rock around... Watch out for the advice that just might be untested. My advice IS tested and I sometimes just get cranky when I hear some of this mumbo jumbo. If my trailer pops rivets, I tell it like it is on the Forum. Folks... Buy M. F. Global stock... they know how to treat their customers... right... don't they.?

[bryanl]

re: "I do not know about your wheels, but my wheels have a 65 psi max air pressure." -- very good point. Wheels have ratings like tires do and those ratings do need respect.

re: "Just a comment, but the tire temperatures mentioned above may be inaccurate, depending on your location. In Arizona, the "cool" running temperature of 120-degrees or less" -- The tire temperatures are reasonably accurate as a rule of thumb. When tires start running at over 140F, the failure rate goes up. This is also related to the speed rating for the tire. If running in hot desert conditions or at high speeds, increase the tire pressure or reduce the speed (or both) to keep tire temperatures at safe levels. There's a lot of issues on this but the fact is that the stuff tires are made of don't like very high temperatures.

Tire temperature is a primary indicator of how the tire is handling its weight load for the speeds being travelled. It is easy to measure on a walkaround and that makes it a good thing to do to keep an eye out for potential tire problems. This is also why temperature is one of the measures available on the better TPMS. -- check it yourself and get your own range of operating tire temperatures that you can use to detect anomalies or potential problems.

re: "the tires will show abnormal wear." -- this is the traditional test for proper tire inflation but most TT tires are replaced due to age and not wear. A bit of extra wear in the center of the tread won't be noticeable unless you put a lot of miles on the trailer every year. That is why many recommend running tires at max sidewall rating rather than try to finagle weight charts and such things as underinflation risks are much more significant than wear risks (usual caveats apply for those seeking to find fault or whatnot)

What with the Airstream suspension, tires aren't usually the major issue for vibration and related problems. The hitch appears to be a more likely suspect on this.

re: "my tire guy advised me to go to a an E rated tire. Any idea why he would recommend this?" -- a lot of times a bit of extra capability can be a good thing, a safety margin. For TT tires, that doesn't seem to be the case.

re: "Watch out for the advice that just might be untested." -- very good advice, I think, but one also has to be careful to evaluate the method of testing. There is a lot of anecdotal 'testing' that doesn't include a decent sample size or account for the many variables often involved in the real world. This is why getting a basic understanding of the underlying technology can be a necessary means to qualify what one hears. Knowing the why and how can help you adapt the experience of others to your own circumstances.

[slowmover]

TT tires need to be at maxmum sidewall pressure.

As Andy indicates, one must spec a tire of the proper load range (12-15% reserve capacity; what is trailer scaled weight?). Tire rim width must be a close match to tread width. An open shoulder traction tread is not ideal, but closed shoulder, etc.

No one is happy with ST tires, deservedly so, thus upsizing to a larger rim (16 or 17") and spec'ng an LT tire of the proper load factor takes more work.

Tire temps can vary in as much as .5 inch. And surface temps are not indicative of what's happening within for given accuracy. Nor do TPMS with valve stem adaptors give "true" temps. Etc. Almost WAG.

But moving to "E" tends to be too much, ideally.

In short, it's hard to get away from ST ( appears they suffer from lack of technological development the past dozen years), but it still appears to be worth the effort.

Individual wheel weights (not just axle average) is best information for starting.

.

[dznf0g]

Originally Posted by REDNAX

TT tires need to be at maxmum sidewall pressure.

As Andy indicates, one must spec a tire of the proper load range (12-15% reserve capacity; what is trailer scaled weight?). Tire rim width must be a close match to tread width. An open shoulder traction tread is not ideal, but closed shoulder, etc.

No one is happy with ST tires, deservedly so, thus upsizing to a larger rim (16 or 17") and spec'ng an LT tire of the proper load factor takes more work.

Tire temps can vary in as much as .5 inch. And surface temps are not indicative of what's happening within for given accuracy. Nor do TPMS with valve stem adaptors give "true" temps. Etc. Almost WAG.

But moving to "E" tends to be too much, ideally.

In short, it's hard to get away from ST ( appears they suffer from lack of technological development the past dozen years), but it still appears to be worth the effort.

Individual wheel weights (not just axle average) is best information for starting.

.

This is all accurate and true...however, one can, through observation, note the "normal" PRESSURE changes while solo traveling over time with TPMS on the TV and draw valid conclusions on what is going on with trailer TPMS PRESSURES. While not a scientific numerically accurate judgement of interior tire surface temp...it's pretty indicative of impending issues of enough significance to predict a potential issue. Pay attention and draw your own conclusions.

[Inland RV Center, In]

Originally Posted by kds

So are there any disadvantages to buying a load E tire? I have 4 year old GM on my trailer now and will be replacing this month. My GW is 7600 and my tire guy advised me to go to a an E rated tire. Any idea why he would recommend this? I thought it would just be for extra safety. He recommended Greenball tires.

Kelly

Kelly.

Your tire guy might be great for cars and trucks, but he obviously knows very little about an Airstream.

Oh, one more thing, he knows how to dig in a persons pocket, too.

Ask him what is the principle method of construction of an Airstream. I'll bet he doesn't have a clue.

Andy

[bryanl]

re: "No one is happy with ST tires, deservedly so" -- this may be common wisdom on these forums but not when it comes to reality. One needs to know the primary reason for tire failures and also to check with the DOT reports. There is a blog by a guy in the RV tire business that has some good stuff on this.

re: "Tire temps can vary in as much as .5 inch. And surface temps are not indicative of what's happening within for given accuracy." -- you measure temperatures in inches?

If you actually measure tire temperatures on the road, you'll find that the variances are not that great and do indeed provide good indication of the tire status.

Also watch out for excess accuracy. That's another problem that shows up a lot. If you find your tires running above 140F they are getting too hot and that goes to the basic nature of the tire materials and construction. If the tires run at below 120F, they have a lot of temperature leeway which means the pressure could be reduced somewhat if desired. I'd be interested if those who actually measure tire temperature, in the desert or in the snow, find otherwise when on the road.

re: "Nor do TPMS with valve stem adaptors give "true" temps." -- that is why I qualified my comment as the 'better' ones (anticipating this sort of knee jerk ad minimus thing that seems too common in these forums where finding fault is preferred over finding knowledge, it seems)

Tire weights and all are fine but a scale for that purpose is a lot less available than an IR thermometer, especially on the road. The weight on a particular tire may also change quite a bit and inferring pressure to use from weight is a calculated, secondary, effort whereas temperature is a primary one.

You do what you want but what I have seen is that keeping an eye on temperature helps me keep my tires properly inflated and catching problems early. Putting them at max sidewall PSI (or within a few psi) in the morning works very well for me.

[Phoenix]

Additional note: When inflating "cold" tires to maximum rated pressure (e.g., load range E tire inflated to 80 psi), it is almost a given that the tire pressure while driving will exceed this value, especially during summer months in the southwest desert. If tire pressure is verified cold, excess pressure should NOT be bled out after the tires heat up. It's OK for this pressure to rise during use; and letting air (or nitrogen) out will result in running the tire slightly underinflated. (My personal experience is that hot tire pressure measurements increase around 4-5 degrees from their original cold value.)

With most tires, underinflation is the highest cause of tire failure in the desert southwest. And, in the summer, one must dodge alligators (tire carcasses) on our highways.

Of course, the exceptions are Goodyear Marathons, whose failures do not seem to be limited to extreme summer temperatures.

[ZoominC6]

I realize there are several threads on tires here on our Forums but I'll wade into this anyway. After hating the GoodYear Marathons and dealing with tread separation issues I went to the Carlisle E rated tires and have been running the same four since 2009. While the air pressure rating is 80psi I run them only at 65psi per my aluminum wheel rating. I utilize Pressure Pros and Centramatic balancers and the after thousands of miles towing this combo has proven to be the best yet. The tires look great as they approach their fourth year on the trailer. I will most likely change out once they get much past the fourth birthday of their manufacture simply because I don't trust any trailer tire closing in on five years of age. Right or wrong, this combo is working well for us and our heavy 30ft Classic S/O Airstream.

[mojo]

ZoominC6, when I bought my first trailer (19' CCD) the previous owner told me he ran the original GM's at around 50 psi for a softer ride. The trailer was 3 years old then and I pumped them up to 65 psi which worked fine for the next year, until one tire started deflating on the Florida Turnpike. No blowout, no nails or cuts. It simply lost the seal on the rim and went dead flat.

Why? Because according to the tire guys, the tire had been run while under inflated for three years which stressed the sidewall to the point it was too soft to hold the bead when the trailer was loaded. After that point, I keep the tires to specified pressure. You may not have experienced any problems yet, but...

[slowmover]

Originally Posted by bryanl

re: "No one is happy with ST tires, deservedly so" -- this may be common wisdom on these forums but not when it comes to reality. One needs to know the primary reason for tire failures and also to check with the DOT reports. There is a blog by a guy in the RV tire business that has some good stuff on this.

re: "Tire temps can vary in as much as .5 inch. And surface temps are not indicative of what's happening within for given accuracy." -- you measure temperatures in inches?

If you actually measure tire temperatures on the road, you'll find that the variances are not that great and do indeed provide good indication of the tire status.

Also watch out for excess accuracy. That's another problem that shows up a lot. If you find your tires running above 140F they are getting too hot and that goes to the basic nature of the tire materials and construction. If the tires run at below 120F, they have a lot of temperature leeway which means the pressure could be reduced somewhat if desired. I'd be interested if those who actually measure tire temperature, in the desert or in the snow, find otherwise when on the road.

re: "Nor do TPMS with valve stem adaptors give "true" temps." -- that is why I qualified my comment as the 'better' ones (anticipating this sort of knee jerk ad minimus thing that seems too common in these forums where finding fault is preferred over finding knowledge, it seems)

Tire weights and all are fine but a scale for that purpose is a lot less available than an IR thermometer, especially on the road. The weight on a particular tire may also change quite a bit and inferring pressure to use from weight is a calculated, secondary, effort whereas temperature is a primary one.

You do what you want but what I have seen is that keeping an eye on temperature helps me keep my tires properly inflated and catching problems early. Putting them at max sidewall PSI (or within a few psi) in the morning works very well for me.

Find us a consensus on any RV board, bubba, about ST tires being acceptable.

The comments I attached about temps, distances, TPMS, etc, were all taken from those made by tire engineers.

If you, or others, need to know how to use a weigh scale to get individual wheel weights (and you don't, but some will) then try asking.


.

[mojo]

Why Use An "ST" Tire

• "ST" tires feature materials and construction to meet the higher load requirements and demands of trailering.
• The polyester cords are bigger than they would be for a comparable "P" or "LT" tire.
• The steel cords have a larger diameter and greater tensile strength to meet the additional load requirements.
• "ST" tire rubber compounds contain more chemicals to resist weather and ozone cracking.