Tire Pressure Question - inflation table, max on door jam sticker vs max for tire

[immortl]

I am looking into TPMS systems for the truck (2009 Dodge Ram 3500 dually long bed, quad cab, 6.7L Cummins) and trailers - Express 8x24 aluminum cargo 9990lb GVW and Keystone Alpine 3900RE 15,000lb GVW. In doing so I was checking out the tires on the pickup and new cargo trailer (not physically at the 5th wheel yet).


For the cargo trailer, the max load rating for the tires is only a tick over 8200lbs, so I think I'll be swapping them out for the Goodyear Endurance E range tires which would exceed the GVW rating. Don't panic, I'll be keeping the overall GVW under the trailer rating of 9990 I'd rather be decently under the max load rating than at the ragged edge.


Now regarding the Goodyear Wrangler Trailrunner AT tires on the pickup - The door jam sticker shows the max axle ratings with tire a pressure of 65psi all around. In looking at the inflation table for the tire (https://tirepressure.com/lt235-80r17-tire-pressure), I see that the load rating at 65psi matches up closely with max axle ratings, exceeding the ratings by a few hundred pounds. That said the table (and specs on the tire) go up to 80psi for the tires but the load ratings there obviously exceed the axle ratings.


My question - would I ever really want to bump the tire pressure up past 65psi in the rear when towing the 5th wheel? Or ought I just keep it in the necessary range for the load on each axle? I need to wander off to the scales here someday and get actual unloaded weights to start with. What do you folks tend to run at tire pressure wise, max pressure or adjust pressure to match the load?


Thanks,
Joe

[jrollf]

Door jamb sticker is MINIMUM cold tire pressure required to carry the Truck's rated max axle load.

Suggest reading through the articles on the RV Tire Safety website. The website is run by a real Tire Engineer, not someone who thinks they are an expert because they had a tire blowout. He cuts through a lot if the mis-information that gets spread around by people in the internet and provides solid advice.

IMHO can't get a better source of tire safety info.

https://www.rvtiresafety.net/

[kdauto]

If you put 4 load range E tires at max pressure of 80 psi you will well exceed the GVWR of the trailer, so it's not recommended nor necessary. You can run them at 80 psi, but the ride will likely suffer and bounce around, probably wearing the trailer out and rougher on the cargo too.

I do exceed the inflation tables by a slight margin many times for fuel economy concerns as well as tire wear issues. Running them super hard when not at a high load will likely cause lots of center wear and you may even find the trailer unstable and bouncy when unladen or lightly loaded.

[Dieselguy4]

The door jam is the pressure I would run in the back. See how it rides and drives at 65 PSI. Going higher will cause you to bounce and chuck with your fifth when on it. The front tires I would run at 75 PSI. If not it will have a lazy handling and the tires will wear faster due to the heavy Cummins engine. I have a 06 Mega Cab SRW and when I try to run anything lower then 75 PSI it wears tires. I also pump up to 80 PSI to tow.

[Dave Pelletier]

Originally Posted by kdauto

If you put 4 load range E tires at max pressure of 80 psi you will well exceed the GVWR of the trailer, so it's not recommended nor necessary. You can run them at 80 psi, but the ride will likely suffer and bounce around, probably wearing the trailer out and rougher on the cargo too.

I do exceed the inflation tables by a slight margin many times for fuel economy concerns as well as tire wear issues. Running them super hard when not at a high load will likely cause lots of center wear and you may even find the trailer unstable and bouncy when unladen or lightly loaded.

This; well said.

Dave

[kdauto]

I misread the part where the O.P. is talking about pressures on the rear of othe TRUCK, not the trailer. Almost the same things apply. i've run 80 psi on my dually rears and it's a bit harsh, also very jumpy and unpredictable on a bumpy curve with no weight in/on the truck.

[Dave Pelletier]

Originally Posted by kdauto

I misread the part where the O.P. is talking about pressures on the rear of othe TRUCK, not the trailer. Almost the same things apply. i've run 80 psi on my dually rears and it's a bit harsh, also very jumpy and unpredictable on a bumpy curve with no weight in/on the truck.

According to the charts, I only need 35 - 40 psi in my dually rears for my load but I use 55-60 as a healthy safety margin.....I probably could go a bit less. 80 is overkill by about 6,000 lbs capacity and has a negative impact on traction, ride and tire life.

Dave

[immortl]

Thanks everyone, I appreciate your responses and feedback.



My take away from the comments above as well as from reading done at the link also provided above, I'll be calculating the pressure needed for the load and then increase that by 10% or so and will go from there and see how everything handles and I can do the tire tread test with chalk or water to make sure the full tire width is in contact. And yeah, I won't be putting the full 80psi in the cargo trailer tires, I'll adjust the pressure to the final weight of the loaded trailer as I'm ready to hit the road. But I'll need the E range tires in order to be able to handle the full 10k GVWR if it ends up weighing that much. With the current tires on it, my GVWR max would be 8200lbs and I suspect once loaded up, we'll be closer to the 10k GVWR and we have 2500 miles or so to go with it.


Found a local Discount Tire place that has the Goodyear Endurances in stock for the cargo trailer and can order in the Carlisles for the motorcycle trailer. I didn't mention this trailer above but I checked the motorcycle trailer out today and saw that its tires needed replacing. They're smaller and Goodyear Endurance aren't made in that size (175/80R13). The Carlisles seem to be decent and the M speed rating on them is good as she drives faster than I'd like for her to when pulling her motorcycle behind. New tires for the trailers, woohoo!



Going to make another post, but while I have your attention here - for aftermarket TPMS, do you guys run all metal valve stems or the high pressure metal shaft but rubber at the wheel stems? One tire place didn't have and couldn't get all metal stems, another didn't sell them but said they'd try to put them on if I provided them but also said they didn't like to use them as they had leaking problems... If the TPMS sensors are the little cap deals is centrifugal force a big concern causing the rubber based stems to leak or causing any damage to them?


Thanks again,
Joe

[jrollf]

I had issues with all rubber ones tearing at the base on my trailer, changed to all metal high pressure valve stems I found on Amazon and haven't had any issues since. (Except the tire place forgot to tighten the stem nuts... ugh) I've never had problems with them leaking. Heck, my F350 has all metal valve stems from the factory.

I haven't tried the metal with rubber base.

[Martian]

If you are asking about metal valve stems for the trailer, be aware of several concerns. Alloy trailer wheels do not accept most metal valve stems but per TST, aluminum stems can be used if you keep them as short as possible and put a little bit of dielectric grease on the threads to prevent corrosion with the brass sensors. If using steel wheels, you have many options of solid brass and steel stems but no matter what kind of wheel you have make sure you get the shortest stem that will allow you to have a sensor that will not stick out past the tire. My tires are balanced without the sensors and they do not seem to bounce with them on as the sensors are a lot closer to the center of rotation than any part of the tire and most of the rim.

[JIMNLIN]

And yeah, I won't be putting the full 80psi in the cargo trailer tires, I'll adjust the pressure to the final weight of the loaded trailer as I'm ready to hit the road. But I'll need the E range tires in order to be able to handle the full 10k GVWR if it ends up weighing that much. With the current tires on it, my GVWR max would be 8200lbs and I suspect once loaded up, we'll be closer to the 10k GVWR and we have 2500 miles or so to go with it.

Its recommended by tire experts and engineers like Roger Marble on rvtiresafety/tire mfg/tire safety blogs/etc that tire on a trailer should never be ran at those minimum tire pressure numbers charts like we do tires on our tow vehicles.
Tires on a trailer side scrub as its pulled around a corner or maneuvering backwards . Watch the tires/wheels while someone is making those moves and it shows side stresses/internal shear as its twisting the tires carcass.
Trailers have close spaced axles in the center of the vehicle unlike a tow vehicle with tires at the corner of the vehicle. Minimum pressures work fine for our trucks as the front tires turn and the rear simply follow.

For those and other reasons I would recommend using max sidewall pressures.

I've pulled trailers with 14"/15"/16"/17.5" (commercially) on trailer with 3500/5200/6k/7k and on up to 12k lbs for over 1.2 million miles so I'm not a newb at wearing out/ruining tires on trailers.
Lessons learned early was never over tire a trailer to the point the tires pressure has to be derated below max sidewall pressures.

Now having said that if the trailer has been over tired with a 80 psi tire then at some point the tire will have to be derated with lower tire pressures so it doesn't wear the centers...but has enough air pressure above a minimum pressure chart to hold the tire shape as it side scrubs around corners/etc.

Never heard of derating a tires pressure on a trailer till I started hanging around rv websites 18 years ago.

[jrollf]

Just be aware when you upgrade to a higher load range, the rated tire pressure on the side wall, in this case 80psi, may actually be higher than the wheel's pressure rating.

[immortl]

I am aware of wheel pressure ratings and have to check the alloy wheels that came with the trailer.


Regarding the tire load range increase, assuming I end up loading the trailer to pretty much near max 10k GVWR, the inflation table found here shows that at 70psi I'd have a margin of 480lbs, 75psi would be 880lbs, and 80psi 1320lbs. I'm thinking somewhere in the 70s ought to be about right and the tire wouldn't be all that under inflated for the sidewall sheer deal, and would be appropriate for the load and tire wear? I need to look up the guides referenced above and learn more.



Have to say, I very much enjoy this forum and learn something new each day that I read it. I appreciate the info and education folks.


Thanks,
Joe