Greystone Tire Inflation Pressure Discussion

[jmgratz]

As softer ride in the trailer is desirable and that is one of the reasons I went with the Mor-Ryde IS. But to decrease the tire inflation, well, are you willing to chance a blow-out due to incorrect inflation? Do you weigh each wheel individually on your rig before each trip to know for sure your weight per the table? I know I don't so I just use the inflation on the sidewall and feel confident I have the proper inflation. To each his own when it comes to inflation but why chance it. Besides this is a no win discussion cause I know in the end you will do what you feel is right and I will do what I feel is right and hopefully we will both arrive at our destinations safely.

 

[jheitman]

As softer ride in the trailer is desirable and that is one of the reasons I went with the Mor-Ryde IS. But to decrease the tire inflation, well, are you willing to chance a blow-out due to incorrect inflation? Do you weigh each wheel individually on your rig before each trip to know for sure your weight per the table? I know I don't so I just use the inflation on the sidewall and feel confident I have the proper inflation. To each his own when it comes to inflation but why chance it. Besides this is a no win discussion cause I know in the end you will do what you feel is right and I will do what I feel is right and hopefully we will both arrive at our destinations safely.

My point exactly. I want to pressurize the trailer tires to the best pressure and I believe that is less than 80 psi. As soon as I weigh all four wheels individually, we'll know what the Load/Inflation table recommended inflation pressure is....

Thanks for taking the time to write guys, keep it coming if you have any additional thoughts

jim

 

[kakampers]

Unless I missed it, which is possible, everyone is missing a very important point!!

You are talking about tires on a trailer...which are subjected to severe twisting and rolling of the sidewall from backing and maneuvering of the unit, which is the nature of the dual-axle set-up. The same tires are not subjected to this when used on motorized vehicles. This is why, in our opinion, it is very important to keep trailer tires inflated to the maximum pressure, REGARDLESS of the load they are carrying...you need to eliminate as much stress on the sidewall as possible...JMHO!

 

[branson4020]

Jim, you are making rocket science out of putting air in a tire.
Run the max sidewall pressure listing.
JMHO.

Peace
Dave

Amen! .....

 

[jheitman]

Unless I missed it, which is possible, everyone is missing a very important point!!

You are talking about tires on a trailer...which are subjected to severe twisting and rolling of the sidewall from backing and maneuvering of the unit, which is the nature of the dual-axle set-up. The same tires are not subjected to this when used on motorized vehicles. This is why, in our opinion, it is very important to keep trailer tires inflated to the maximum pressure, REGARDLESS of the load they are carrying...you need to eliminate as much stress on the sidewall as possible...JMHO!

Important point Indeed.

I remember the first time I tried a turn the trialer a lot at one time. I looked at the tires and they were significantly offset from each other, that is twisted on the rims in the direction of the axels. Question is, is this harder on a tire with maximum air pressure or on a tire with reduced air pressure? I don't know, but I know that this is a significant consideration, thanks for bringing it up.

We have to find a tire expert that can address these concerns from the tire design perspective. Maybe I'll try calling the tire companies and see if I can get into the engineering department.

Thanks again,

jim

 

[jmgratz]

Last year at the Escapade in Sedalia Missouri we (DW and I) attended the RVer Boot Camp. One of the sessions was about tire safety. The presenter was a retired tire engineer from Goodyear. This man (can't recall his name at the moment) helped design the tires. He is an expert in the field. He retired after over 35 years with Goodyear. I asked him the very question regarding tire inflation, i.e. should the tire be inflated to the manufacturers sticker or what is printed on the tire sidewall. He said he recommended inflating the tire to what is the maximum cold pressure printed on the sidewall. His reasoning was RV tires are subject to more variable conditions than the average tire such as elevation changes, barometric pressure changes, temperature changes, load changes etc. Also since we RVers don't weigh our units everytime we use it (do you weigh it everytime you move it from campground to campground) and we are constantly loading and unloading, adding and removing water etc, it make sense to use the max inflation. So I go by the tire expert. Everyone else can do what they believe is the right thing to do. Hapy RVing

 

[jnbhobe]

For 40 years I have run nothing but the max inflation and have not had one problem I won't change now

 

[caissiel]

Well said ,
I do believe the tire expert is right.
No use taking a chance just to think you get a softer ride with a few pounds less in a tire.. Its not worth it.

As for the bounce of a hard tire, I feel that the harder the tire the less wear and tear on the suspension because it will not bounce as much as a soft tire. it will hit harder but will not bounce with 3500Lbs siting on it. we are not talking about an empty utility trailer.

I never have less then 75Lbs in my truck rear tires and I travel loaded or empty at any time. So I never change the pressure, and the good Ford don't bounce, the shocks do their work well and if it does not I change the shocks.

I use to drive rough sporty Mustangs because on our roads the passenger cars did not last, The car was great on tires, suspensions and it never needed suspension repairs. One time I checked the pressure in a tire and it was past 40LBS it did not ride any rougher then normal.

 

[jheitman]

Guys:

OK, we have come a long way in one day of discussion. I feel honored to have access to your opinions. Thanks for all the inputs.

Here are the major points I have noted so far:

1) Trailer tires should always be inflated to the maximum pressure listed on the tire sidewall

2) Any pressure less than the max on the sidewall is considered under inflated and risks a blowout from sidewall fatigue

3) Utilization excess loads need to be considered, highway slope, highway turns, low speed, large angle turning of tandom axel configuration, i.e. General Trailering

4) Higher pressures lead to less suspension movement and lower suspension wear over time

5) If trailer tire loads are to be measured, each tire needs to be measured individually to consider side to side load differences

I have been proposing that a better/safer condition might be to inflate tires based on their max expected load, plus some margin for variations. You load up your trailer and measure each wheel. There is plenty of support for setting vehicle tire pressures this way within the tire industry. I think my tire loads are significantly lower than my tire maximum load ratings, and a lower pressure is worth consideration. My tires are made in China and perhaps all margin is needed to cover that fact... Anyway, here is another significant source of tire information from the RV Safety and Education Foundation. FYI.

http://www.rvsafety.com/custompagedc2f.html?pg=weighingreport

This article suggests measuring and using the tables for vehicles (motorhomes and trucks) and using tire side wall ratings for trailers, just as I've been told a couple times before. This fits with what GM said about their trucks. The exception for trailers is because of the excessive "squirming" trailer tires experience in turning they said, as also suggested by KAKAMPERS, way to go. This is only one reference, but a pretty important one from relatively official RV industry folks.

Well, there's some supported rationale for max pressure tire inflation on a trailer, in addition to many identical inputs from just about everyone. The only exception RSEF noted was when addressing a ride issue, which I was to some extent. I think I'll write to RSEF and get more information from them on 5th wheels in particular.

I'm going to weigh my trailer tomorrow anyway, just to see how much the side to side variation actually is, I'll let you know, FYI.

Any Additional Comments,

jim

 

[lwmcguir]

If you are looking to improve the ride, the best way is to add the CP air equalizer. You will be very happy with it.

 

[jheitman]

I wrote to RVSEF and Walter Cannon called me today and we talked over this subject. Although he recognizes the method of weighing and using a table to set pressure, he really recommneded that in my specific case that I use the side wall pressure. Here is the note he sent me today:

"I must caution about setting tire pressure without knowing individual wheel
loads. This is the only way to accurately determine the proper inflation
pressure, the side to side differential can and most often is significant.
Simply using an axle load and dividing can result in catastrophic results.
Since I do not see you in our data base I have nothing to go on and cannot
give any advice other than maintain 'Side Wall' pressure.
This answer although not exactly what you want to hear is the only thing a
tire, chassis, trailer manufacturer or safety educator can give.

With individual wheel loads; all the above would recommend basing the tire
inflation on the heaviest side of the axle and add a 200 - 500 pound safety
margin.

Walter C. Cannon
Executive Director
RV Safety & Education Foundation"

I have written Michelin and TreadIt the people who supply tire assemblies to Heartland. We'll see what they recommend too. I'm still going to weigh my rig today just to see how the weights distribute over the four tires.

jim

 

[Elevatorman]

Well said ,
I do believe the tire expert is right.
No use taking a chance just to think you get a softer ride with a few pounds less in a tire.. Its not worth it.

As for the bounce of a hard tire, I feel that the harder the tire the less wear and tear on the suspension because it will not bounce as much as a soft tire. it will hit harder but will not bounce with 3500Lbs siting on it. we are not talking about an empty utility trailer.

I never have less then 75Lbs in my truck rear tires and I travel loaded or empty at any time. So I never change the pressure, and the good Ford don't bounce, the shocks do their work well and if it does not I change the shocks.

I use to drive rough sporty Mustangs because on our roads the passenger cars did not last, The car was great on tires, suspensions and it never needed suspension repairs. One time I checked the pressure in a tire and it was past 40LBS it did not ride any rougher then normal.

Shocks doing their job. Most of us with these large fifth wheels have the shocks mounted at such a steep angle by the factory, that they couldn't be working as they should, putting most of the bounce, (and stress) on the tires. Therefore reducing the margin of error on load capacities on the tires and springs. Caissiel I see you re-mounted you upper shock mounts. Are you still running the Freestars on the BC? Adding the work of a good shock may decrease the added loads the tires and springs see while traveling. Maybe an upgraded shock may be the answer also. Interesting!

 

[jheitman]

Shocks doing their job. Most of us with these large fifth wheels have the shocks mounted at such a steep angle by the factory, that they couldn't be working as they should, putting most of the bounce, (and stress) on the tires. Therefore reducing the margin of error on load capacities on the tires and springs. Caissiel I see you re-mounted you upper shock mounts. Are you still running the Freestars on the BC? Adding the work of a good shock may decrease the added loads the tires and springs see while traveling. Maybe an upgraded shock may be the answer also. Interesting!

Thanks for the suggestion, but the Greystone 32RE does not have any shocks, I wish it did.

 

[jheitman]

So I went to the scales today and made three measurements. From these I have calculated the following weights: (click on icon to get full image)



My left rear trailer tire is the most heavily loaded at 2540 lbs. If I add a 400 lbs margin to that my worst case weight would be 3040 lbs. From the Load/Inflation table, I should have about 70 psi in all my trailer tires. This isn't much less than the side wall pressure of 80 psi. Sounds like I should stick with the 80 psi, I know everyone would agree, but it takes me a little while to come around, only two days really.

Any comments on the weight distribution? I might have the trailer aft a bit lower than the forward part...

jim

 

[Gaffer]

What is your rear truck axel load rating?

 

[jheitman]

What is your rear truck axel load rating?

Here are the truck specifications:
Truck GVWR 9200
Excess Load Capacity 3167
Max Trailer Weight 12400
GCWR 18500
R GAWR 6084
F GAWR 4200
Max Tounge Weight 2500


I've got quite a bit of margin on the axels, but only 500 lbs to go with the GVWR.

These weights were with all our gear in the trailer, a full tank of gas and both myself and my wife sitting in the truck.
There were only a couple of gallons of water in the black tank. I've got 800 lbs of margin against the GCWR.

jim
2010 Chevy Silverado, Ext Cab, 4x4, 6.0 L Vortec
2011 Greystone 32RE
Reese Select Plus 20k Slider Hitch

 

[Dave012]

I just run them at maximum. All the time spent weighing the axles, checking tire pressure, looking at tables, etc is time spent not having a beer and enjoying camping. Alternatively, I could have a beer when doing all that work, but I'm pretty sure that would result in a safety issue.

 

[jheitman]

I wrote to RVSEF and Walter Cannon called me today and we talked over this subject. Although he recognizes the method of weighing and using a table to set pressure, he really recommneded that in my specific case that I use the side wall pressure. Here is the note he sent me today:

"I must caution about setting tire pressure without knowing individual wheel
loads. This is the only way to accurately determine the proper inflation
pressure, the side to side differential can and most often is significant.
Simply using an axle load and dividing can result in catastrophic results.
Since I do not see you in our data base I have nothing to go on and cannot
give any advice other than maintain 'Side Wall' pressure.
This answer although not exactly what you want to hear is the only thing a
tire, chassis, trailer manufacturer or safety educator can give.

With individual wheel loads; all the above would recommend basing the tire
inflation on the heaviest side of the axle and add a 200 - 500 pound safety
margin.

Walter C. Cannon
Executive Director
RV Safety & Education Foundation"

I have written Michelin and TredIt the people who supply tire assemblies to Heartland. We'll see what they recommend too. I'm still going to weigh my rig today just to see how the weights distribute over the four tires.

jim

TredIt, providers of tires to Heartland RV, also recommends inflating my TowMax tires to 80 psi, as marked on the side wall. Michelin has mailed me a booklet covering RV and trailer tires, we'll see what that says.

I think the conventional weighing and Load/Inflation Table technique is great for normal vehicles, motorhomes and trucks, but not good for 5th wheel trailers. The main reason for over inflating the trailer tires, from a conventional sense, is that they experience a lot of transverse loading because trailers tend to walk around a bit from side to side. This wiggling is greatly reduced in 5th wheel trailers, but still there. This effect happens all the time but more on winding highways or when changing lanes, anything to add sideways momentum to the trailer. Tires are heated by a number of effects, one is this wiggling from side to side which flexes the sidewall. Other contributors to heating include effects like rolling resistance. We can't reduce the sideways wiggling effects, but we can reduce others like rolling resistance by inflating the tire to maximum pressure so it rolls easier, reducing this component of heating. Lower trailer tire temperature translates to longer life and safer operation. Rolling easier might also help with gas mileage too.

Another effect is related to having twin axels usually very close together. When it turns it wants to turn around a single point, but with two axels the tires end up scuffing laterally. You can really see this effect when you try to back the trailer at a large angle to the TV. When you do this you are mainly rotating the trailer without much fore/aft travel. You can see that the tires get well out of alignment from one another. (I don't think I'm going to back this way anymore, instead I'll make big turns using smaller increments followed by straighten the TV and TT). Anyway this twin axel effect also load the sidewalls at speed and causes heating not seen with normal vehicles.

I may not have all these effects described exactly right, but I think I have the general concepts. Please comment if you see this differently, especially if I'm just plain wrong.....

Walter Cannon of RVSEF suggests monitoring all RV tires closely at rest stops. He suggested watching for sidewall blisters and especially for any parts of the tread which start to break off. He also indicated monitoring the temperature of the tires. One method would be to lay your hand on the tire, he said they might be hot, but not so hot that you couldn't hold your hand on them. I've ordered a small inexpensive infrared thermometer and Walter said they work great too. The thermometers allow you to establish a numerical baseline temperature for each tire, then you can recognize when one starts to heat abnormally. I'm going to be especially watching that driver side aft tire which has the highest load.

With all the bad press on Chineese tires, I'm not sure I'm going to keep my PowerKing tires more than a season, but I'll try to get some use out of them, with lots of monitoring. It took a couple days for me to give up using Load/Inflation Tables for trailers, but I get it now. Thanks guys...

jim

 

[cemill]

I think you are making a moutain out of a mole hill. Over my lifetime of camping and pulling various campers along with several class A motorhomes I have always inflated the tires to the recomended max pressure as stamped on the tire itself and to this date have never had a blowout due to underinflation.
If you inflate to around 40 to 50 lbs. on a 80 pound tire, you are setting yourself up for a tire failure.

 

[jheitman]

I think you are making a moutain out of a mole hill. Over my lifetime of camping and pulling various campers along with several class A motorhomes I have always inflated the tires to the recomended max pressure as stamped on the tire itself and to this date have never had a blowout due to underinflation.
If you inflate to around 40 to 50 lbs. on a 80 pound tire, you are setting yourself up for a tire failure.

I now agree with you 100%. Thanks for the input.

jim