Travel Trailer Tire Pressure

My old Goodyear Marathon tires on my 34' Jayco were getting some age on them, so I decided it was time to replace them.  I tried to do a lot of research on tires, but seemed to get more confused, the more I read!  In the end, I settled on 205/75/R14 Goodyear Endurance.  I read a lot of promising things about them and coupled with the fact that they're not made in China, I figured I'd give them a shot. 

The sidewall indicates that they should be inflated to 65 PSI.  The sticker on my trailer, however, states that my tires should be inflated to 50 PSI.  My concern is that I've read that under-inflated tires tend to build up a lot of heat.  So, on my first run with the new tires today, I left them at 65 PSI and drove two hours.  Within about 25 minutes, my tire pressure monitoring system showed their pressure at 73 PSI and the average temperature of the tire at around 97 degrees.  Those numbers stayed consistent for the duration of the trip.  In case it matters, it was in the mid-80's for the outside temperature and my trailer's weight is usually just a little under its maximum of 7,500 pounds.

So, my question is this:  Should I continue to run them at the tire manufacturer's recommended pressure of 65 PSI, drop it down to the trailer's recommended inflation of 50 PSI, or inflate them to some pressure in between?  I'd really appreciate any insight or advice anyone can give me.

First of all, the tire pressure on the sidewall of the tire doesn't say that the tire SHOULD be inflated to that number.  That is the Maximum tire pressure (cold pressure) that the tire can safely be inflated to.

Next question.....are the tire that you just put on the trailer the same exact size as the OEM tires....in other words, did the trailer, when new, start out with tires sized at 205/75/R14?  If so, then go by the sticker on the trailer....50psi.

http://www.rvforum.net/SMF_forum/index.php/topic,98845.0.html

xrated said:

Next question.....are the tire that you just put on the trailer the same exact size as the OEM tires....in other words, did the trailer, when new, start out with tires sized at 205/75/R14?

Click to expand...

Thanks for the reply.  Yes, I made certain to purchase tires that were of identical size as the ones that came on the trailer.  I've read a lot about how bad it is to run on under-inflated tires, and how it's best to go with the pressure stamped on the tire's sidewall, so I've been leery about dropping the the pressure down 15 PSI to match the trailer's sticker recommendation.

On the other hand, if the trailer's sticker is the absolute best guide, I want to follow its recommendation.

Tire with the same physical size can still have different max load capacity.  If the new tires have a max load rating at 65 psi, but the previous ones were 50 psi, odds are the new tires are Load Range D while the originals were Load Range C.

Assuming the original ties were adequate to support the trailer weight at 50 psi, the same would be true of the new ones. However, the news one have a greater max capacity, and inflating to 65 gains that extra capability. Since most RV trailers come from the factory with barely adequate tires capacity, I would use some of the extra capability of the Load Range D tire and inflate to 60 or 65 psi.  There is no real downside in doing so, though the trailer may ride a bit rougher and shake things around inside a bit more.

If you would post the trailer axle GAWRs, we could be a bit more scientific about the necessary inflation and probably even suggest an optimal inflation for those tires. The trailer GVWR and axle GAWRs will be on a sticker or plate somewhere on the left front side. Probably the same place the tire size and psi recommendations are.

The sticker your looking at was for the OEM installed tires, and was likely the maximum pressure rated for that tire.  As a general rule of thumb a person should always inflate trailer tires to the max as listed on the tire sidewall for maximum load carrying capadity.  Remember, properly inflated tires run cooler.  Heat is one major tire killer.

As a general rule of thumb a person should always inflate trailer tires to the max as listed on the tire sidewall for maximum load carrying capadity.

Click to expand...

True, as far as it goes, but it's better to have the tires inflated more in keeping with the actual load. Sometimes on trailers there's not a lot of difference between the two, but some will have larger differences. Be careful about an "always" rule...

Gary RV_Wizard said:

Tire with the same physical size can still have different max load capacity.  If the new tires have a max load rating at 65 psi, but the previous ones were 50 psi, odds are the new tires are Load Range D while the originals were Load Range C.

Assuming the original ties were adequate to support the trailer weight at 50 psi, the same would be true of the new ones. However, the news one have a greater max capacity, and inflating to 65 gains that extra capability. Since most RV trailers come from the factory with barely adequate tires capacity, I would use some of the extra capability of the Load Range D tire and inflate to 60 or 65 psi.  There is no real downside in doing so, though the trailer may ride a bit rougher and shake things around inside a bit more.

If you would post the trailer axle GAWRs, we could be a bit more scientific about the necessary inflation and probably even suggest an optimal inflation for those tires. The trailer GVWR and axle GAWRs will be on a sticker or plate somewhere on the left front side. Probably the same place the tire size and psi recommendations are.

Click to expand...

Thanks, Gary.  That helps a lot.  To answer your question, the GVWR is 7,500 pounds, while each axle's GAWR is 3,500 (it is a dual-axle trailer).  I'm assuming, then, that I'm safe to run these tires at 65 PSI and that the 7 PSI increase while driving is nothing to be concerned with.  Am I correct?

donn said:

The sticker your looking at was for the OEM installed tires, and was likely the maximum pressure rated for that tire.  As a general rule of thumb a person should always inflate trailer tires to the max as listed on the tire sidewall for maximum load carrying capadity.  Remember, properly inflated tires run cooler.  Heat is one major tire killer.

Click to expand...

Inflating to the maximum pressure listed on the sidewall of a tire serves no useful purpose if it is not needed, from a load carrying capacity standpoint.  And, I don't believe that is a general rule of thumb....maybe for some folks, but be careful advising generalities when that may not be the case.

Ok, here is the issue:
Over invlated tires wear out faster in the center thus reducing tire life, also the reduced contact area with the road reduces control (more likely to fishtail)

Under inflated tires are more likely to suffer side wall failure, wear at the edges instead of the center and again reduce control.

Properly inflated tires the FULL tread engages the road for maximum tire life and maximum control.  It is thus desierable to have PROPER pressure.

Only one way to insure that.]

Scale the wheel.. Not the entire trailer but each wheel. (If you have dual axles you can do the pair but each side)

Inflate to TIRE Manufacturer's recommendations for the load they carry. Some like to add  a few (5) PSI I support that.  NOTE Entry and Service (Curb and Traffic) may be different pressures.

Since RV trailer tires are near-always marginally sized for the load, the "rule of thumb" cited above is an OK one for RV trailers.  If that results in over-inflation by 10-15 psi, that is rarely a concern with trailer tires, whereas even a couple lbs under-inflation is likely to have serious repercussions.

Note that we are talking about inflation over the minimum specified for the loaded weight. Most tire experts recommend running 5-10 psi above the minimum for the load, to allow for unexpected load increases, ambient temperature changes, etc. The tire engineers have designed the tire to work well and safely in that range. Even the max load & psi data stamped on the sidewall is the minimum psi for that load and there need be no concern about going 5-10 psi above that when cold. Even though it will increase even more as the tire heats up.  It will still be within its design envelope.

By definition, any "rule of thumb" is a substitute for proper measurement and analysis. The intent is to provide reasonably safe & useful results when the time or skill to do something "the right way" is lacking. A rule of thumb rarely gives optimal results, but it generally avoids major problems.

I'm assuming, then, that I'm safe to run these tires at 65 PSI and that the 7 PSI increase while driving is nothing to be concerned with.  Am I correct?

Click to expand...

Yes. A 12%-15% increase in tire pressure from "cold" to "hot" is quite normal.

I have the Goodyear Endurance on my 5er, I got home day before yesterday from a 2,930 mile trip (trailer miles) for a total of 4,298 miles on the tires. 

Mine are load range E 16" but I run them at max cold pressure of 80 psi and while running 375 - 470 miles a day the pressure goes up to about 87 PSI and a temp of 95? to 102?.  The air temps were mid to upper 90's.

I hope this comparison may be a little help to you.

The question about increased tire inflation pressures while the vehicle is in use  - rolling down the road at highway speeds - seems to often end up in inflation pressure threads. Wheel & tire manufacturers account for the thermal dynamic increases and decreases and all are factored into the process of determining cold recommended tire inflation pressures.

People that often monitor their tire temps become aware what is normal and what is above the red line, so to speak. If you want to read-up on the subject,  just type thermal equilibrium, (tires) in your computers search engine.

I?m not fond of ?rule of thumb? information. It?s kind of like windage and elevation, always changing.

Here is a short version of what the tire industry standards have to say about the tire inflation pressures found on the vehicle?s federal certification label.

Some of them will get wishy-washy about it but search deep enough and you?ll find they are really saying the same thing as all others.

They will never knowingly recommend using less inflation pressure than what has been recommended by the vehicle manufacturer for Original Equipment (OE) tires. The minimum pressure for plus sized tires approved by the vehicle manufacturer may differ from what is recommended by the tire placard. However, the OE tire provides the standard, replacements must provide a load capacity equal to or greater than what the OE tires provided. That is done with inflation pressure. NHTSA approves the use of auxiliary tire information stickers to show the new tires physical size and recommended inflation pressures. Those stickers should be placed adjacent  to the original placard. A notation should also be put in the vehicle owner?s manual.

A replacement tire of the same size with a higher load capacity does not fall into the plus sized category. The existing tire placard will have the correct inflation pressure of 50 PSI for - lets say a LRC tire - and that amount of inflation pressure in a like sized tire with a LRD load capacity will provide the identical load capacity at 50 PSI. Maybe by changing brands you can find a more durable tire but the load capacity at the recommended inflation pressure of 50 PSI will still be the same when it comes to load capacity. To gain load capacity reserves with the LRD tire more inflation pressure is necessary.

The majority of the manufacturers of ST tires say they are designed to be operated full time at their recommended sidewall pressures. Only by getting the actual weights supported by individual wheel position can a satisfactory tire inflation pressure be obtained. Lowering any inflation pressure below vehicle manufacturer recommendations is just asking for trailer tire problems.

I am a fan of the you tube channel Long Long Honeymoon. Based on their experience (with many miles and multiple tire failures), they have found the most success with and recommend 2-3 lbs below the 65 psi max pressure on their TT.  I run ours at 63 cold psi. I use a digital gauge. I also check all the tire, wheel, brake drum, hub, etc. temps of both the TV and TT with a hand held infrared temp gun after a long run as soon as I get out of the TV.

I am a fan of the you tube channel Long Long Honeymoon. Based on their experience (with many miles and multiple tire failures), they have found the most success with and recommend 2-3 lbs below the 65 psi max pressure on their TT.  I run ours at 63 cold psi.

Click to expand...

Sorry, but that seems terribly ill-advised to me. Using a tire pressure because somebody else does is about the worst way I can think of to set tire pressure. What is optimum for one trailer is all but guaranteed to be non-optimum for another.

Unless you know your trailer tires are the same size and carry the same weight as another trailer, how can you judge that the pressure they use is a good choice for your rig?  The max load pressure is related to the load rating and 65 psi is pretty much standard max load pressure for LRD tires. Simply because your tires have the same max doesn't mean everything else should be the same.  Maybe the Long Long Honeymoon people don't need quite the max, but without using scaled weights and an inflation table, there is no way to know if yours needs more or could do with less.

Fortunately, in this case you are still close to the max load inflation pressure, so maybe it is still ok. It's the logic of using the same psi as someone else that is downright scary to me. That is the antithesis of wise tire inflation. Each of us should be inflating tires based on the weight load and tire size on our rig, not somebody elses.

The recommended tire inflation pressures for RV trailers is not arbitrary, it?s a result of a standard order given to the vehicle manufacturers in the regulations they must follow to properly certify the vehicle?s safety. The standard says, in part, that the vehicle manufacturer must set the minimum cold recommended inflation pressures for all Original Equipment tires fitted to the vehicle at time of first sale. Those pressures must be appropriate for the fitments.

Tire manufacturers provide the recommended cold inflation pressures for the maximum load capacity of a tire. It?s on the tire?s sidewall.

Inflation pressures higher than the vehicle manufacturer?s cold recommendations and lower than the tire manufacturers pressures listed on the tire?s sidewall are commonly known as load capacity reserves. This is the area where adjustments, when needed, are made. However, 95% - 100% of all trailer tire fitments are set at the tire?s maximum allowable inflation pressures for the maximum load. So, in that case there is no room for any adjustments. Lowering them below vehicle manufacturer recommendations is counterproductive and not recommended.

Note: Automotive tire fitments require the vehicle manufacturer to provide a percentage of load capacity reserves. There is no provision in that standard requiring RV trailer tire fitments to have any load capacity reserves. It?s - IMO - a fallacy in the FMVSS standards that was allowed to continue during the last round of NHTSA rules committee meetings (2007). 

Gary RV_Wizard said:

Sorry, but that seems terribly ill-advised to me. Using a tire pressure because somebody else does is about the worst way I can think of to set tire pressure. What is optimum for one trailer is all but guaranteed to be non-optimum for another.

Unless you know your trailer tires are the same size and carry the same weight as another trailer, how can you judge that the pressure they use is a good choice for your rig?  The max load pressure is related to the load rating and 65 psi is pretty much standard max load pressure for LRD tires. Simply because your tires have the same max doesn't mean everything else should be the same.  Maybe the Long Long Honeymoon people don't need quite the max, but without using scaled weights and an inflation table, there is no way to know if yours needs more or could do with less.

Fortunately, in this case you are still close to the max load inflation pressure, so maybe it is still ok. It's the logic of using the same psi as someone else that is downright scary to me. That is the antithesis of wise tire inflation. Each of us should be inflating tires based on the weight load and tire size on our rig, not somebody elses.

Click to expand...

I guess I should have mentioned the manufacturer's recommended tire pressure is 65 on our TT. I can not seem to delete my own post; feel free to do so if you are a moderator since my comments seem ill-advised.

No need to delete it - you are entitled to your opinion.  I merely just explaining my disagreement with it.