Tire pressures

[prstlk]

This has probably been asked before but because we are leaving in the AM for the summer I need quick advise from the folks on here.

We have a 2013 Ford F350 SRW 6.7L Diesel and a new to us 2016 Keystone Cougar 30' fifth wheel.

We just put on 4 new Goodyear Endurance tires on the 5th wheel. The tire says to run at 80psi and that is what the tire company put in them.

The label on the 5th wheel says to run 65psi in the tires.

Which should we follow? One of us says the label recommendation and the other says the tire recommendation.

What say you? Please advise!

[Cummins12V98]

fj12ryder wrote:
With my rear duallies, I run 65 psi. Full pressure of 80 psi is rated to over 12,000 lbs. A little overkill for a 7,000 lb. load. 🙂 65 psi should still give me over 10,000 lbs. of capacity.

My DRW rear tires inflated to 65psi covers my 9,750# RAWR.

[fj12ryder]

With my rear duallies, I run 65 psi. Full pressure of 80 psi is rated to over 12,000 lbs. A little overkill for a 7,000 lb. load. 🙂 65 psi should still give me over 10,000 lbs. of capacity.

[MFL]

The OP has not returned, probably due to his leaving to travel? It may also be due to so many opinions, that every tire thread encounters.

Since Jim mentioned Tireman 9, who is a well known TE, and an actual owner of many types of RVs and trailers, I'll mention a few things I learned.

First thing...comparing your truck tire inflation, to multi- axle trailer tire inflation is apples/oranges.

Trailer tire charts have a purpose, and give the absolute minimum pressure required to support the weight you have on them. This, the reason to add a bit of pressure to number given on the chart. How much? Some say 5 psi, which can be right for the tire application they have.

However, a better choice, if using charts for ST tires, is to add 10% to the chart minimum pressure as a true minimum, and 20% better yet, if not over the sidewall indicated max. So on a smaller ST tire, the chart shows 50 psi for your exact weight given, you would add 5 psi minimum, (10%), keeping in mind, this is a minimum. Using percent, rather than an exact psi of say 5, will fit many size tires.

In most cases, using the proper ST tire, shown on the placard of your trailer, the best choice is max tire pressure shown, on that tire. In some cases, that may be just barely adequate, and going up one load range, may be better. If so, most times, using that ST tire at max sidewall pressure, will allow coolest running, best handling.

Truck tires...I'll just say that I run my fronts according to door sticker, all the time. My door sticker shows 80 psi in rear, which I use under heavy load, and lower to 65-70 in rear with light load.

Jerry

[JIMNLIN]

Tireman9 rvtire safety blog) wrote:
https://www.rvtiresafety.net/2018/02/tire-inflation-not-same-for-all-trailers.html

Roger has many articles on reasons for sidewall tire pressures for trailers vs a truck or a MH.

**What we discovered after the overnight computer run, was that in simply S turns (similar to seen in the video) the belts on a multi axle trailer were developing 24% higher internal shear forces than the tires on the truck pulling the trailer.**

Now if the rv trailer owner did something silly like and over tired the trailer such as mounting a load G tire on 6k/5.2k axle then max sidewall pressure will be too much. Then those minimum pressure/load charts plus another 10-15 percent would work best.

Tireman9 tire blog covers many aspects of tires for rvs. And more important the reasons tires on trailers with close spaced axle work in a more severe environment than tires at the front/rear corner on a tow vehicle/MH.
Good read for education purposes from a tire engineer perspective.

[fj12ryder]

Personally I don't see that trailer tires take any more of a beating than the tow vehicle tires. I run my rear duallie tires down around 65 psi. That's plenty of capacity for the load, about 7,000 lbs, and it doesn't beat us up as bad. Fronts run around 70 psi due to the Cummins up there. I usually run the trailer tires based on load plus 5 psi.

[twodownzero]

While I don't do it on the truck, I always inflate the trailer tires to the maximum pressure on the sidewall even if they're not at maximum load. Tires on trailers really take a beating and get hot, and I want every advantage I can muster to avoid any issues. In your case, I would probably not lose sleep running them at 65 psi, but I wouldn't do it anyway.

My truck actually specs only 75 psi on the rear for maximum load and I never follow that either because the truck needs all the rear tire capacity available to be able to carry the full GVWR, so I run those at 80 psi too.

Fronts I keep at the door sticker pressure, which I think is 50 psi. There's no need for more than that up there as most of the trailer weight is on the rear axle.

[Cummins12V98]

Retired JSO wrote:

prstlk wrote:
This has probably been asked before but because we are leaving in the AM for the summer I need quick advise from the folks on here.

We have a 2013 Ford F350 SRW 6.7L Diesel and a new to us 2016 Keystone Cougar 30' fifth wheel.

We just put on 4 new Goodyear Endurance tires on the 5th wheel. The tire says to run at 80psi and that is what the tire company put in them.

The label on the 5th wheel says to run 65psi in the tires.

Which should we follow? One of us says the label recommendation and the other says the tire recommendation.

What say you? Please advise!

Not to start an argument, but apparently the OP’s trailer was equipped with D rated tires and the load sticker shows proper pressure. Many ST tires do not have a web page showing pressure vs load. That’s the reason for using sidewall listed pressurization .

All tires have a load/inflation chart. Simply look up size and load range.

REPEAT, listed sidewall pressure only states capacity at it's max PSI. NEVER says inflate to XX psi.

[Retired_JSO]

prstlk wrote:
This has probably been asked before but because we are leaving in the AM for the summer I need quick advise from the folks on here.

We have a 2013 Ford F350 SRW 6.7L Diesel and a new to us 2016 Keystone Cougar 30' fifth wheel.

We just put on 4 new Goodyear Endurance tires on the 5th wheel. The tire says to run at 80psi and that is what the tire company put in them.

The label on the 5th wheel says to run 65psi in the tires.

Which should we follow? One of us says the label recommendation and the other says the tire recommendation.

What say you? Please advise!

Not to start an argument, but apparently the OP’s trailer was equipped with D rated tires and the load sticker shows proper pressure. Many ST tires do not have a web page showing pressure vs load. That’s the reason for using sidewall listed pressurization .

[Cummins12V98]

TXiceman wrote:

Retired JSO wrote:
65 psi was for a D rated tire. The new tires are E rated and 80 PSI. Run the new tires At 80 cold. As temperatures warm, you may need to adjust the cold PSI.

You need to weigh the RV and adjust the tire pressure to match the manufacturers weight loading chart. Add 5 psig to the rated pressures. Also watch tire wear patterns for center or should wear which would indicate over or under pressure.

Operating the tire at maximum pressure could cause excessive center wear and an excessively rough ride.

And you do not adjust pressures as the tires warm during the day. Tire pressures are set according to pressure after the rig has set for 4 hours and no direct sun on the tires. I usually set my pressures first thing in the morning. As the seasons warm or cool, you will need to make seasonal adjustments of your starting air pressure.

Ken

Dang I thought I was reading one of my posts. Nice to see several are understanding how to properly inflate tires.

One thing to add is overinflation will cause reduced braking with a smaller contact patch.

Just made it to my NW Summer digs and now have 67,000 miles on my 6 Michelins on my truck. Without proper inflation that would not have happened. OH, also my 4 rear tires are carrying 10k near 1/2 of those miles.

[TXiceman]

Retired JSO wrote:
65 psi was for a D rated tire. The new tires are E rated and 80 PSI. Run the new tires At 80 cold. As temperatures warm, you may need to adjust the cold PSI.

You need to weigh the RV and adjust the tire pressure to match the manufacturers weight loading chart. Add 5 psig to the rated pressures. Also watch tire wear patterns for center or should wear which would indicate over or under pressure.

Operating the tire at maximum pressure could cause excessive center wear and an excessively rough ride.

And you do not adjust pressures as the tires warm during the day. Tire pressures are set according to pressure after the rig has set for 4 hours and no direct sun on the tires. I usually set my pressures first thing in the morning. As the seasons warm or cool, you will need to make seasonal adjustments of your starting air pressure.

Ken

[Cummins12V98]

Mike134 wrote:
I swapped from C to D tires on my trailer and ran them at the full 65 PSI, old ones were recommended for 50 PSI.

That caused just the center of the tire to wear out but hey at least I didn't have to worry about them aging out LOL. Now I run them around 50-53 psi per the GY inflation tables and CAT scale results, which gives me uniform tire wear across the tread.

Another "CHICKEN DINNER" !!!!!!!!!

[Cummins12V98]

Retired JSO wrote:
65 psi was for a D rated tire. The new tires are E rated and 80 PSI. Run the new tires At 80 cold. As temperatures warm, you may need to adjust the cold PSI.

PLEASE explain WHY you say to run the "E" tires at 80psi?

[Mike134]

I swapped from C to D tires on my trailer and ran them at the full 65 PSI, old ones were recommended for 50 PSI.

That caused just the center of the tire to wear out but hey at least I didn't have to worry about them aging out LOL. Now I run them around 50-53 psi per the GY inflation tables and CAT scale results, which gives me uniform tire wear across the tread.

[Retired_JSO]

65 psi was for a D rated tire. The new tires are E rated and 80 PSI. Run the new tires At 80 cold. As temperatures warm, you may need to adjust the cold PSI.