Tire Pressure for Upgraded Load Rating Tires

[TheWolfPaq82]

I use this logic: Every popup, TT, I've ever owned stated to keep tires inflated to a certain PSI. That PSI was "Always" the same as the "Max" pressure marked on the sidewall of the tire on the trailer. If the Load was a "C" with a Max of 50, the trailer sticker said 50. If the Load was a "D" with a Max of 65, the trailer sticker said 65. If I went to an "E" Load, I'd fill the tire to Max PSI on the tire. This is how I roll.

[danking49]

Originally Posted by TheWolfPaq82

I use this logic: Every popup, TT, I've ever owned stated to keep tires inflated to a certain PSI. That PSI was "Always" the same as the "Max" pressure marked on the sidewall of the tire on the trailer. If the Load was a "C" with a Max of 50, the trailer sticker said 50. If the Load was a "D" with a Max of 65, the trailer sticker said 65. If I went to an "E" Load, I'd fill the tire to Max PSI on the tire. This is how I roll.

I actually planned to stop by my local RV dealer and check a bunch of stickers with just that suspicion. I'm betting all the TT stickers will have the load range max # of the tires installed.

[babock]

Originally Posted by TheWolfPaq82

I use this logic: Every popup, TT, I've ever owned stated to keep tires inflated to a certain PSI. That PSI was "Always" the same as the "Max" pressure marked on the sidewall of the tire on the trailer. If the Load was a "C" with a Max of 50, the trailer sticker said 50. If the Load was a "D" with a Max of 65, the trailer sticker said 65. If I went to an "E" Load, I'd fill the tire to Max PSI on the tire. This is how I roll.

That's because they use the lowest low range they can to meet the load requirement. They would never put a load range D on if a C was adequate.


If you have a load range C on a trailer and have it filled at 50 PSI and take that identical trailer with identical load and put a load range E on it and fill to 50 PSI, the sidewall will run at the exact temp or lower and still have less sidewall flex.

[67L48]

Originally Posted by danking49

[...] There seems to be two schools of thought here with little consensus. Run them at max pressure [...]; or run them at the original lower range C pressure [...]

No, definitely not and that's not what was said above. Option number two is wrong, wrong, wrong. (Remember, we're talking about upgraded load ratings here, not OEM tires.)

Either operate at max rated pressure of that tire (check sidewall) OR

Operate at the recommended pressure from the manufacturer that supports the trailer's weight. That has nothing to do with the original lower pressure. The minute you put a different tire on that trailer that isn't identical to the OEM, then take a sharpie and cross out all of the tire info on the trailer's sticker. It's now garbage.

Here is an example from Maxxis. Here is an example from Goodyear. If you go option 2 and decide that max pressure is egregious, then you need to refer to this type of chart from your tire manufacturer. Based on the trailer weight, you would select your tires' pressures based on the chart. This has nothing to do with the old, outdated placard that gives recommendations for the OEM tires.

• Run max pressure as specified on the sidewall of your ST tire, OR
• Run the pressure recommended by your tire manufacturer for the load you are carrying

Hope this helps.

[babock]

Originally Posted by 67L48

No, definitely not and that's not what was said above. Option number two is wrong, wrong, wrong. (Remember, we're talking about upgraded load ratings here, not OEM tires.)

Either operate at max rated pressure of that tire (check sidewall) OR

Operate at the recommended pressure from the manufacturer that supports the trailer's weight. That has nothing to do with the original lower pressure. The minute you put a different tire on that trailer that isn't identical to the OEM, then take a sharpie and cross out all of the tire info on the trailer's sticker. It's now garbage.

Here is an example from Maxxis. Here is an example from Goodyear. If you go option 2 and decide that max pressure is egregious, then you need to refer to this type of chart from your tire manufacturer. Based on the trailer weight, you would select your tires' pressures based on the chart. This has nothing to do with the old, outdated placard that gives recommendations for the OEM tires.

• Run max pressure as specified on the sidewall of your ST tire, OR
• Run the pressure recommended by your tire manufacturer for the load you are carrying

Hope this helps.

He was already WAY under the load limit of a load range C. He says he is currently at 1100#/tire. A load range D at max PSI is 2150#.


Running 50 PSI with his new load range D tire gives him a load rating of 1820#/tire. That's a 65% margin. Seems like plenty and doesn't stiffen up his ride unnecessarily.

[danking49]

Originally Posted by 67L48

No, definitely not and that's not what was said above. Option number two is wrong, wrong, wrong. (Remember, we're talking about upgraded load ratings here, not OEM tires.)

Either operate at max rated pressure of that tire (check sidewall) OR

Operate at the recommended pressure from the manufacturer that supports the trailer's weight. That has nothing to do with the original lower pressure. The minute you put a different tire on that trailer that isn't identical to the OEM, then take a sharpie and cross out all of the tire info on the trailer's sticker. It's now garbage.

Here is an example from Maxxis. If you go option 2 and decide that max pressure is egregious, then you need to refer to this type of chart from your tire manufacturer. Based on the trailer weight, you would select your tires' pressures based on the chart. This has nothing to do with the old, outdated placard that gives recommendations for the OEM tires.

• Run max pressure as specified on the sidewall of your ST tire, OR
• Run the pressure recommended by your tire manufacturer for the load you are carrying

Hope this helps.

This logic of using tire inflation charts doesn't fly with my situation. Let's start with a necessary assumption. "trailers" are by definition, variable weight vehicles. Campers somewhat so, boat trailers big time. IMHO, actual trailer weight is irrelevant for trailer tire decisions. Only actual maximum axle load capacity matters.

So, with that assumption in mind, the original tires on my camper were 205/75R14 load range C. The camper sticker listed those as the correct tire, and said they were to be inflated to 50#. According to all the tire charts I’ve seen, that equates to a 1760# load capacity. The axles on this trailer are both 2200# capacity. So, while the actual maximum load per tire on this rig is only 1100#, the manufacturer is telling me to inflate the tire to 660# (roughly 50%) over the max load capacity of the axle it’s riding on. What does this tell me? It tells me that using those tire charts to calculate inflation pressure doesn’t include other factors like dynamic loads (bumps, water sloshing around etc) and temporary overloads like what happens with a flat tire etc. If I use the charts to set the tire pressure in this situation, it would be 25# for a load capacity of 1170#. Does anyone think it would be a good idea to pull a trailer down the freeway for 500 miles at 70mph with only 25#s of air in the tires? Not me!

I can get to the original trailer manufacturers tire load capacity of 1760# by simply running my new load range D tires at 50#; as is implied as okay by Goodyear’s chart. While that is probably the best solution for keeping as much tire on the road as possible for stability and softening the ride a little bit, would it allow too much sidewall flex and result in premature tire failure?

I’ve decided to just split the difference, run the new load range D tires at 60# to keep a little more tread on the road for stability and be done with it. I did a test run yesterday with 65# on those shiny new Goodyear Endurance tires and the trailer felt a lot more squirrely than it ever did on the original Akuret “China Bombs” that ran stable and solid at 50#. I’m hoping dropping down to 60# will improve the ride; if not I’ll try 55#; but no lower.

[67L48]

I think you have made a tremendous amount of assumptions about what the Forest River folks may or may not have calculated and, as a result, have complicated the situation.

I'll go ahead and stay with my recommendation for non-OEM tires. Either run max pressure of the new tires' sidewalls or follow the tire manufacturer's recommendations for pressure/capacity.

Cheers.

[Airdale]

In this post my reference material is from the governing body (DOT, NHTSA & FMVSS) and tire industry standards (USTMA). Keep in mind that the Federal Motor Carrier Safety Association (FMCSA) tire regulations are not applicable to RV trailer or pick-up truck tire fitments and will not be addressed. So, if you think something I say is missing you are probably thinking commercial.

The recommended cold inflation pressures found on vehicle certification labels are set by the vehicle manufacturer and are considered by all regulations and standards to be the minimum requirement for Original Equipment (OE) tires. Optional inflation pressures will start at what has been recommended and end at what is displayed on the tire sidewall for maximum load capacity. (That option seldom exists with OE trailer tires).

All recommended cold inflation pressures for replacement tires must provide a load capacity equal to or greater than what the OE tires provided. The U.S. Tire Manufacturing Association says to NEVER use inflation pressures below vehicle manufacturer cold recommendations.

Load inflation charts do not provide recommendations. Their information is factual and given in increments for manufacturers and installers to reference for accurately setting and establishing recommended cold inflation pressures.

[jadatis]

Calculated with my made calculator
4767lbs gvwr , 4 tires 2040 lbs AT 65 PSI.
Gives 44 psi.

The old C- load , 1760lbsAT 50 psi
Gave 39 psi

When using a WDH , there is more weight on the axles/ tires , then advice 46 psi. ( new D-load)

This with maximum reserve , and no screws trembling loose , and livetime of 6 years or more.

You often see this lower needed pressure for tandem-axle trailers.

The D- load needs higher pressure for the same load, because its stiffer, so gives lesser surface on the ground with same deflection.
But in official American lists all the loadranges are given in the same pressure/ loadcapacity-list.
European tiremakers give seperate list for every loadrange/ plyrating of same sise.

So if you feel fine at 50 psi, you can safely use that, 65 psi will certainly give bumping.

Did you experiënce sighns of bumping with the old C-loads at 50 psi?

[danking49]

Originally Posted by jadatis

Calculated with my made calculator
4767lbs gvwr , 4 tires 2040 lbs AT 65 PSI.
Gives 44 psi.

The old C- load , 1760lbsAT 50 psi
Gave 39 psi

When using a WDH , there is more weight on the axles/ tires , then advice 46 psi. ( new D-load)

This with maximum reserve , and no screws trembling loose , and livetime of 6 years or more.

You often see this lower needed pressure for tandem-axle trailers.

The D- load needs higher pressure for the same load, because its stiffer, so gives lesser surface on the ground with same deflection.
But in official American lists all the loadranges are given in the same pressure/ loadcapacity-list.
European tiremakers give seperate list for every loadrange/ plyrating of same sise.

So if you feel fine at 50 psi, you can safely use that, 65 psi will certainly give bumping.

Did you experiënce sighns of bumping with the old C-loads at 50 psi?

Not sure what you mean by "bumping"; but the trailer rode fine on the old C-loads at 50 psi, but felt very busy or jittery with the new D-loads at 65 psi. I'll try 60 psi on the next trip out and see how that works.

[jadatis]

Signs of bumping , for instance scews coming loose from woodwork, or doors being open after the ride, when not locked. On tires centrewear.

But now you know how low you can go for savety of tires, and that is 46 psi. I would dare to go to 55 psi directly, but you must do what feels fine to your idea.

[Witch Doctor]

Originally Posted by jadatis

Signs of bumping , for instance scews coming loose from woodwork, or doors being open after the ride, when not locked. On tires centrewear.

But now you know how low you can go for savety of tires, and that is 46 psi. I would dare to go to 55 psi directly, but you must do what feels fine to your idea.

of course you did read these are ST tires “D” and you recommend to the OP that 46 psi is safe to drive on? Did I read this correctly?

[jadatis]

Originally Posted by Witch Doctor

of course you did read these are ST tires “D” and you recommend to the OP that 46 psi is safe to drive on? Did I read this correctly?

The tires have maxload of 2050 each, so 4x on 2 axles is total 8200 lbs , of wich 2 x 2200= 4400 lbs used. I lowered this , because ST, with system the tiremakers also use, and I worked out, to 4x 1710lbs= 6840 lbs, and added 11% to the 4400 before putting it in my determined extra safe formula.
This gives maximum reserve, with no bumping.

So I dare to state, that if not overloaded, and everything is measured 100% acurate( never possible ) this is perfectly safe. So the reserve is for that inacuracy and weightdivision R/L, etc.

Most single axle trailers,need with my calculation even higher pressure then behind AT, wich the tiremakers dont allow anymore, they did allow it up to about 10 years ago.

[Airdale]

Originally Posted by jadatis

The tires have maxload of 2050 each, so 4x on 2 axles is total 8200 lbs , of wich 2 x 2200= 4400 lbs used. I lowered this , because ST, with system the tiremakers also use, and I worked out, to 4x 1710lbs= 6840 lbs, and added 11% to the 4400 before putting it in my determined extra safe formula.
This gives maximum reserve, with no bumping.

So I dare to state, that if not overloaded, and everything is measured 100% acurate( never possible ) this is perfectly safe. So the reserve is for that inacuracy and weightdivision R/L, etc.

Most single axle trailers,need with my calculation even higher pressure then behind AT, wich the tiremakers dont allow anymore, they did allow it up to about 10 years ago.

I know your logic is sound but you have to remember that our (USA) tire industry standards are not always going to jive with your logic. For instance, our tire industry safety factors are designed to protect the entire field and are standardized for that purpose. I'm providing a link below to the USTMA standards document. On page #43 in the RV section there is a statement that reinforces the recommended cold inflation pressures set by vehicle manufacturers for all vehicles. The statement says to NEVER use inflation pressures below what has been set for the OE tires by the vehicle manufacturer. Link that statement to another that says all replacement tires MUST provide a load capacity equal to what the OE tires provided reinforces the NEVER below cold recommended.

https://www.ustires.org/sites/defaul...TruckTires.pdf

[jadatis]

The OEM advice of TT maker here is 50 psi.
Standardisation is ok, but is introduced to prevent damage.

If now OEM advice is to low to laws of nature, must we then follow that advice, to the idea of that article you gave, yes, go and destroy your tires, because TT maker prescribes it.

And in this case, using 65 psi of new tires, gives bumping, bad gripp and centrewear of tires. Do we want that. So for most tandem axle trailers, to laws of nature, lower then standard is better.

Lower pressure gives the tires the possibility to turn around the same centre,, because slipp-angle can be more, and no overheating because of the maximum reserve I build in.

I calculate now for 5 years or more with this system in Holland, and will ask around on fora, if someone had good or bad experiënces with my advices.

[Witch Doctor]

Originally Posted by jadatis

The OEM advice of TT maker here is 50 psi.
Standardisation is ok, but is introduced to prevent damage.

If now OEM advice is to low to laws of nature, must we then follow that advice, to the idea of that article you gave, yes, go and destroy your tires, because TT maker prescribes it.

And in this case, using 65 psi of new tires, gives bumping, bad gripp and centrewear of tires. Do we want that. So for most tandem axle trailers, to laws of nature, lower then standard is better.

Lower pressure gives the tires the possibility to turn around the same centre,, because slipp-angle can be more, and no overheating because of the maximum reserve I build in.

I calculate now for 5 years or more with this system in Holland, and will ask around on fora, if someone had good or bad experiënces with my advices.

really? What a joke, I’m sorry but your information is a accident waiting to happen , your stating that a “d” rated ST tire and with a CP of 65 is all right to deflate to your 46 psi and run on that ? I don’t think there anybody on this forum or any other forum or any other would recommend this for a ST tire. REALLy

[babock]

Originally Posted by Witch Doctor

really? What a joke, I’m sorry but your information is a accident waiting to happen , your stating that a “d” rated ST tire and with a CP of 65 is all right to deflate to your 46 psi and run on that ? I don’t think there anybody on this forum or any other forum or any other would recommend this for a ST tire. REALLy

Curious..if he had E rated tires, would you want him to air up to 80PSI? 50PSI would be just fine and stated so in the tire manufacturer inflation tables. Even at 50PSI, he has 65% margin with 1100# load per tire.

[Girtski]

Originally Posted by bedubya

If you run at max pressure, with considerably less than max weight, you probably won't have the maximum amount of tread on the road.

You will also be rearranging the maximum amount of cargo in your camper since it will be all over the place from the tires running at such a high inflation.😁

[RockyMtnMarty]

please go to

http://www.Rvtiresafety.net

You all can learn from the the premier expert about tires, tire pressures and load ranges etc. Roger Marble has 40 years experience as a tire design engineer. His blog is the bible for questions like these. Don't make safety decisions from a million opinions.

[ebergler]

the sidewall stated pressure on tires is a maximum pressure! If you manufacturer says a certain pressure, say 50#, stay there with the higher rated tires!
higher pressure means higher vibration, which is uncomfortable in an RV and can destroy your trailer.
I even go 5# lower than my rig says, because the vibration is so much better. Yes, I burn a bit for fuel, but it is worth it!
If you have any worries about destroying you tires, feel them after going a while, and if they are handwarm and not hot, you are doing OK!
personally I would not want to drive a tire at the stated max rating shown!