Altitude, temperature and tire pressure questions

Jim the G114 weighs just 60 lbs, which is the same as my R250's!!!!! And only 2.5 lbs more than the G614. So I do not think weight is an issue with the G114.

Here is the load chart for the 215/75R17.5 LRH tire
80 3375
85 3540
90 3695
95 3860
100 4010
105 4180
110 4330
115 4495
120 4650
125 4805

Chris

Thoughts ??
Your HH Discover America has 7k axles and has a 16200 GVWR. Now subtract 3k pin and your looking at approx 13k-14k on the axles or 3250 lbs to 3500 lbs per tire.
looking at a 17.5 Goodyear G114 H tire says they have a 4800 lb rating at 125 psi. Now you have a H tire with lets say a 3500 lb load. That means your going to have to derate the tires pressure significantly. I don't have a chart but lets just say down to 100 psi. Now the H tire is a big heavy tire and big heavy tires heat fast and can quite high temps especially carrying a 3500 lb load with those lower pressures. The tire is hot and pressure builds.
Now on the flip side if the H tires were carrying a 4200-4400 lb load and the pressure was cold set at 125 those tires will operate cooler. There is a trade off when we over tire a trailer.
As others have said tire makers know a tire heats with speed and ambient temps. I have no idea how much pressure would be the best for your tire situation other than weigh your trailer axles and divide by four = load per tire and consult your tire makers pressure charts.

Its been my experience with several equipment trailers on the road in the high passes in northern NM/CO tire pressure wasn't affected by altitude.

I like this suggestion for a over tired trailer;

rvsafety.com
Tire Load and Inflation Ratings

Note: Towable – Travel Trailer/ 5th Wheel owners Due to the severe use conditions experienced by tires when axles are very close together – tire industry experts recommend maximum (sidewall) inflation pressure for towable tires unless this causes a sever over-inflation situation (20psi+), often referred to as the ‘basketball effect’. If this is your situation allow a 10 – 15psi safety margin above the minimum required inflation pressure.

When I'm running on a full load - I stay with the 125psi in the morning. I would only adjust when returning on empty - which is kinda rare in my business.

stripit wrote:
I also have the H rater 125 psi tires on my rig. With the weights I'm carrying on those tires I really need 105 psi to carry safely. At 105 starting out pressure in the Az heat my TST system will show the tires end up at about 132 psi. So as an experiment the next day of travel I increased the pressure to 110 psi start out and they climbed up to 132 ish. Next time we moved I tried 115 psi start and they climbed to 132 ish. I did one final test at 115 psi and again 132 ish So these tires like to run on my rig at the 132 area and temps depending on the outside temps hovered about 20 degrees over ambient. On a hot Az day the outside can hit 112 so the tires are running in the 135 to 140 degree range, but that isn't the normal here. Normally 20 over whatever the temps are.

Interesting numbers Stripit. I was wondering or thinking is a better term on how the pressures would change as you described.
chevman

I also have the H rater 125 psi tires on my rig. With the weights I'm carrying on those tires I really need 105 psi to carry safely. At 105 starting out pressure in the Az heat my TST system will show the tires end up at about 132 psi. So as an experiment the next day of travel I increased the pressure to 110 psi start out and they climbed up to 132 ish. Next time we moved I tried 115 psi start and they climbed to 132 ish. I did one final test at 115 psi and again 132 ish So these tires like to run on my rig at the 132 area and temps depending on the outside temps hovered about 20 degrees over ambient. On a hot Az day the outside can hit 112 so the tires are running in the 135 to 140 degree range, but that isn't the normal here. Normally 20 over whatever the temps are.

Cold is after the tires have been sitting for a few hours and before you start driving on them, forget about temp. If you do not fully air the tires then you are driving with underinflated tires which causes increased heat and damages tires, don't try to compensate since you dont know how much to compensate. What are your tires heat ratings? If you don't know then contact your tire dealer or the tire manufacturer and ask. If you don't know the max heat your tire is rated for then you don't know what you are checking for when you use the temp gun to check the tire temp, you just wasted the money for the gun and your time checking the tire temp.

Personally I don't worry about it. I check the tire pressures a day or two before we leave on a trip(long), usually don't bother for a short one, as we get ready. I might check them later in trip, but not usually. Two or three weeks and 4k to 5k later we are home. I have never had a tire issue on this now 8 1/2 year old rig. A couple days ago had the OEM tires replaced as we prep for a long trip, they were almost 10 years old. They were LT's mounted on 110 psi rated wheels on 5080# rated axles. Good job Keystone. JME.

I have recently gotten a Tire Traker system and am leaving on a long trip soon. Can someone explain how the readings relate to the above discussion. Why wouldn't you get an alarm as the tires heated up? Also my gauge doesn't agree with the TPMS. Do I get another gauge or adjust the tires to the TPMS readings or what? Thanks for any help.

Bob

I'm no tire expert. So I'll just say what I experienced on a recent trip. I run on GY G614s, max cold pressure 110 psi. I run mine at 105 cold. I also have the TST tire pressure monitoring system which shows both pressure and temperature. I just returned from the 5800 mile trip where we went up through the western mountains and back. I checked the pressure every morning before hitching up and the cold pressures were 105 +/- 3 psi. After running for an hour or so the pressures ran 115 +/- 3 psi. The temps were affected a bit by the ambient temps but not a great deal. Trip elevations were from ~600 ft (home) up to ~11,000 ft (Eisenhower tunnel on I-70 in CO). The running pressures seemed to be affected more by the running temps than by the elevation changes. Just my experience.

X2 on Me Again. Now, the sleep number bed, that is another issue with altitude.