Tire inflation vs altitude vs load distribution

[P & T]

Originally Posted by sourdough

Your Surge Guard is a good unit, I have the same unit without the remote monitor. It has saved my bacon many times. If you're throwing the breakers inside the RV the Surge Guard won't help you if an individual RV circuit is overloaded. Each side of the EMS will carry 50A and your individual circuits in the RV will be 15 and 20A. If the park power is crappy and falls outside acceptable limits the EMS will shut down. If you're overloading individual circuits, which it sounds like, you need to see what is running inside when it trips the breaker(s). If trying to run 3 A/Cs at once 2 will be on one leg and that's probably what's doing it.

When we got to the park yesterday, there was 119v on L1 and 114v on L2. As the afternoon progressed; L1=117v & L2=112v. The bedroom AC and main living AC are on one 50amp leg (they were both tripping). The garage AC stayed running. Just to experiment, I ran the garage AC only and just the fans on the bedroom and main AC's...nothing tripped from that point on. My surge protector does do high and low voltage protection down to 102v (the other one recommended does high and low voltage protection too).

Ohms law states that when volts go down, amps go up.

I don't think I ever saw anything below 102v to cause a "protect mode" shutoff. When I returned to the site today, it was comical to see the park had emptied out significantly (probably because everyone was hot and done with crappy electrical), but the voltage was at 119v on L1 & L2.

My suspicion is that with both AC's which were tripping, they were at the cusp of the 15a each with park voltage drops. All of the rigs in the park on a 102 degree + day were sucking juice.
Regardless, we got to see our daughter graduate from nursing school today and her condo AC has been keeping us cool the past few days. Ready to head home tomorrow and watch my TPMS stuff for the next 600 miles in two days.

Thanks everyone!

[sourdough]

Originally Posted by P & T

When we got to the park yesterday, there was 119v on L1 and 114v on L2. As the afternoon progressed; L1=117v & L2=112v. The bedroom AC and main living AC are on one 50amp leg (they were both tripping). The garage AC stayed running. Just to experiment, I ran the garage AC only and just the fans on the bedroom and main AC's...nothing tripped from that point on. My surge protector does do high and low voltage protection down to 102v (the other one recommended does high and low voltage protection too).

Ohms law states that when volts go down, amps go up.

I don't think I ever saw anything below 102v to cause a "protect mode" shutoff. When I returned to the site today, it was comical to see the park had emptied out significantly (probably because everyone was hot and done with crappy electrical), but the voltage was at 119v on L1 & L2.

My suspicion is that with both AC's which were tripping, they were at the cusp of the 15a each with park voltage drops. All of the rigs in the park on a 102 degree + day were sucking juice.
Regardless, we got to see our daughter graduate from nursing school today and her condo AC has been keeping us cool the past few days. Ready to head home tomorrow and watch my TPMS stuff for the next 600 miles in two days.

Thanks everyone!

Others with 3 A/Cs will have to chime in as I don't have 3 but trying to run 2 A/Cs on one leg and they both hit startup mode, which I'm sure was happening in 102+ degree weather, I figure is going to trip your breaker especially if you are running a little low on voltage - acceptable voltage but not enough to carry that kind of load.

[rlh1957]

Set It and leave it alone.

Fill up to Cold Pressure and leave it.
You’re overthinking and complicating it.

Driving it will be different sunny-side vs. shade-side. Don’t sweat it.
Pressure will go up during day while driving. Altitude Pressures don’t change enough to worry about. I don’t know anyone that adjust pressure up or down based on altitude. Roads you drive will be under 12,000 ft.
Only a sudden altitude change expanding and contracting could stress tires and no way could you ever changed altitude pressure that quick. Only an aircraft could do that.
Enjoy the trip!

[LeeSpice]

I also have the Salin Tires with a max of 110lbs (think they're the same model as yours) I've been worried because they're Chinese tires and I had a chinese tire explode on me about 3 years ago. On a smaller trailer, they were trailer Kings. I read the Reviews on the Salin and they seem much more heavy duty, so I've left them on (for now). On tire pressures I was also religiously putting them at 110lb cold. But in May I was traveling in San Antonio and spoke to a tire shop and the friendly guy said you don't need 110lbs unless you're running max load on the tire, which I think is about 4K pounds. I found a table for this. Actually you should be inflating the tire based on the load on the tire. I calculated the weight and backed off to 95lbs, based on the table. The guy at the shop said it's better not to overinflate the tire since the trailer rides better and the tire can deflect in response to road hazards (as opposed to failing).

[Ddaddyo]

Have you ever seen a Truck Driver checking and adjusting Air Pressure? It's much more Critical on an 80,000# Rig.

[travelin texans]

Originally Posted by LeeSpice

I also have the Salin Tires with a max of 110lbs (think they're the same model as yours) I've been worried because they're Chinese tires and I had a chinese tire explode on me about 3 years ago. On a smaller trailer, they were trailer Kings. I read the Reviews on the Salin and they seem much more heavy duty, so I've left them on (for now). On tire pressures I was also religiously putting them at 110lb cold. But in May I was traveling in San Antonio and spoke to a tire shop and the friendly guy said you don't need 110lbs unless you're running max load on the tire, which I think is about 4K pounds. I found a table for this. Actually you should be inflating the tire based on the load on the tire. I calculated the weight and backed off to 95lbs, based on the table. The guy at the shop said it's better not to overinflate the tire since the trailer rides better and the tire can deflect in response to road hazards (as opposed to failing).

I'd have to disagree with that tire guy!
IMHO 15 psi below is under inflated which, as I said my opinion, is worse than the possibility of a rougher ride being aired to the recommended pressures. Under inflation creates more heat which is one of the causes for tire failure.
By that recommendation if you at some point need to travel with full tanks, haul couple more lawn chairs, DW adds more shoes you'll need to reweigh the rv then inflate the tires accordingly for the extra weight.
As RLH mentioned, inflate to either the rv manufacturers recommended pressures or the cold sidewall pressures & check them again some time later on, DONE!

[notanlines]

Lee, what Danny^^^^said. Your friendly tire guy is mistaken.

[CWtheMan]

Originally Posted by notanlines

Lee, what Danny^^^^said. Your friendly tire guy is mistaken.

The "tire guy" might be right. RV trailer tires installed under the guidance of FMVSS are only required to carry the total weight of the vehicle certified GAWRs.

On another note. Tire industry standards require replacement tires to have a load capacity equal to or greater than the OE tires.

No one likes this, but it's what NHTSA says. The correct cold inflation pressures for your tires can be found on the vehicle certification label, vehicle owner's manual and on the tire load and inflation placard.

Once the replacement tires have had their cold inflation pressures set by the installer, inflation from the recommended cold to the value molded on the tire sidewall becomes optional.

Tire manufacturers may offer recommendations above the vehicle certified recommended cold inflation pressures. But keep in mind that vehicle manufacturers are the only ones allowed to set recommended cold inflation pressures for OE/OEM tires.

[jadatis]

My opinion is not maniacaly change pressures, but others here indicated that already.

But I have 2 things you can use to better understand how this all works.

One is that TMPS sends absolute pressure to the unit, wich substacts 14.7psi average ambiënt presdure at sealevel from it, and presents this to you on the screen.
So on a altitude where for instance 11.7 psi, is 3 psi lower, TMPS gives at same temprature same pressure, while a gauge, wich measures overpressure, then gives 3 psi higher.
There are some, that write that absolute pressure, carries the load, if true, you need to fill or measure with a gauge on that hight 3 psi higher, while tmps gives 3 psi lower then gauge after that.

Second is a list for cold filled pressure at 70 degrF, and degrF change / 1 psi.
Then you can roughly calculate by head what the temperature in tire is by pressure change.
But also what pressure cold to fill at other then 70 degrF.
But if you use it for 60 degrF cold filled, it will not give dramatic differences.

Here the list.

35 psi/ 10,5 F/psi
36 psi/ 10,5 F/psi
37 psi/ 10 F/psi
39 psi/ 10 F/ps
40 psi/ 9,5 F/psi
42 psi/ 9,5 F/psi
43 psi/ 9 F/psi
45 psi/ 9 F/psi
46 psi/ 8,5 F/psi
49 psi/ 8,5 F/psi
50 psi/ 8 F/psi
53 psi/ 8 F/psi
54 psi/ 7,5 F/psi
58 psi/ 7,5 F/psi
59 psi/ 7 F/psi
63 psi/ 7 F/psi
64 psi/ 6,5 F/psi
70 psi/ 6,5 F/psi
71 psi/ 6 F/psi
77 psi/ 6 F/psi
78 psi/ 5,5 F/psi
86 psi/ 5,5 F/psi
87 psi/ 5 F/psi
96 psi/ 5 F/psi
97 psi/ 4,5 F/psi
109 psi/ 4,5 F/psi
110 psi/ 4 F/psi
126 psi/ 4 F/psi
127 psi/ 3,5 F/psi
148 psi/ 3,5 F/psi
149 psi/ 3 F/psi
177 psi/ 3 F/ps

[flybouy]

Originally Posted by jadatis

My opinion is not maniacaly change pressures, but others here indicated that already.

But I have 2 things you can use to better understand how this all works.

One is that TMPS sends absolute pressure to the unit, wich substacts 14.7psi average ambiënt presdure at sealevel from it, and presents this to you on the screen.
So on a altitude where for instance 11.7 psi, is 3 psi lower, TMPS gives at same temprature same pressure, while a gauge, wich measures overpressure, then gives 3 psi higher.
There are some, that write that absolute pressure, carries the load, if true, you need to fill or measure with a gauge on that hight 3 psi higher, while tmps gives 3 psi lower then gauge after that.

Second is a list for cold filled pressure at 70 degrF, and degrF change / 1 psi.
Then you can roughly calculate by head what the temperature in tire is by pressure change.
But also what pressure cold to fill at other then 70 degrF.
But if you use it for 60 degrF cold filled, it will not give dramatic differences.

Here the list.

35 psi/ 10,5 F/psi
36 psi/ 10,5 F/psi
37 psi/ 10 F/psi
39 psi/ 10 F/ps
40 psi/ 9,5 F/psi
42 psi/ 9,5 F/psi
43 psi/ 9 F/psi
45 psi/ 9 F/psi
46 psi/ 8,5 F/psi
49 psi/ 8,5 F/psi
50 psi/ 8 F/psi
53 psi/ 8 F/psi
54 psi/ 7,5 F/psi
58 psi/ 7,5 F/psi
59 psi/ 7 F/psi
63 psi/ 7 F/psi
64 psi/ 6,5 F/psi
70 psi/ 6,5 F/psi
71 psi/ 6 F/psi
77 psi/ 6 F/psi
78 psi/ 5,5 F/psi
86 psi/ 5,5 F/psi
87 psi/ 5 F/psi
96 psi/ 5 F/psi
97 psi/ 4,5 F/psi
109 psi/ 4,5 F/psi
110 psi/ 4 F/psi
126 psi/ 4 F/psi
127 psi/ 3,5 F/psi
148 psi/ 3,5 F/psi
149 psi/ 3 F/psi
177 psi/ 3 F/ps

"Holy $hit, where's the Tylenol!."

[P & T]

Originally Posted by jadatis

My opinion is not maniacaly change pressures, but others here indicated that already.

But I have 2 things you can use to better understand how this all works.

One is that TMPS sends absolute pressure to the unit, wich substacts 14.7psi average ambiënt presdure at sealevel from it, and presents this to you on the screen.
So on a altitude where for instance 11.7 psi, is 3 psi lower, TMPS gives at same temprature same pressure, while a gauge, wich measures overpressure, then gives 3 psi higher.
There are some, that write that absolute pressure, carries the load, if true, you need to fill or measure with a gauge on that hight 3 psi higher, while tmps gives 3 psi lower then gauge after that.

Second is a list for cold filled pressure at 70 degrF, and degrF change / 1 psi.
Then you can roughly calculate by head what the temperature in tire is by pressure change.
But also what pressure cold to fill at other then 70 degrF.
But if you use it for 60 degrF cold filled, it will not give dramatic differences.

Here the list.

35 psi/ 10,5 F/psi
36 psi/ 10,5 F/psi
37 psi/ 10 F/psi
39 psi/ 10 F/ps
40 psi/ 9,5 F/psi
42 psi/ 9,5 F/psi
43 psi/ 9 F/psi
45 psi/ 9 F/psi
46 psi/ 8,5 F/psi
49 psi/ 8,5 F/psi
50 psi/ 8 F/psi
53 psi/ 8 F/psi
54 psi/ 7,5 F/psi
58 psi/ 7,5 F/psi
59 psi/ 7 F/psi
63 psi/ 7 F/psi
64 psi/ 6,5 F/psi
70 psi/ 6,5 F/psi
71 psi/ 6 F/psi
77 psi/ 6 F/psi
78 psi/ 5,5 F/psi
86 psi/ 5,5 F/psi
87 psi/ 5 F/psi
96 psi/ 5 F/psi
97 psi/ 4,5 F/psi
109 psi/ 4,5 F/psi
110 psi/ 4 F/psi
126 psi/ 4 F/psi
127 psi/ 3,5 F/psi
148 psi/ 3,5 F/psi
149 psi/ 3 F/psi
177 psi/ 3 F/ps

So one of the things I noticed was that one of my tires (tire #4; passenger middle) was dropping in pressure, or lower, than the rest at times, but then would go back up. I thought there was a slow leak at first but then I started to think about humidity at fill up...talk about over thinking. If one tire took more air than the others, and the humidity was different at that time from the original fill up, I guess it could change pressure at a different rate.

I did not think about absolute pressure on the TPMS but that makes sense because my digital gauge was reading as the delta with the given altitude and was always different the TPMS readings at higher elevations.

You all have given me a lot of great info and insight for my OCD. I'll probably just pick a cool morning and bleed some air out of my tires, pump them all to 110 and just monitor for leaks on each road trip. Which is probably all I should have done to begin with but this new found knowledge is invaluable.

Thanks!

[notanlines]

"pick a cool morning and bleed some air out of my tires, pump them all to 110 and just monitor for leaks on each road trip."
An exceedingly good idea.

[jadatis]

Also the infuence of humidity I did research.
In the cold pressure influence of that is marginal.
Will make a list for that to, but for now, 100% humidity, the partial pressure of water is related to the temperature.
Boiling point of water 212 degrF, 100% humidity is 14.7 psi, so at average ambiënt pressure it can go on evaporating.
But in a tire with 110psi if enaugh liquid water still partial pressure of water as gas is 14.7 psi.
At 70degrF PP H2O 0.33psi.
So that lower pressure wich goes back must have another reason, mayby a slow reacting tmps sensor.

[wiredgeorge]

This discussion has wandered off into the TWILIGHT ZONE.

[jadatis]

I think, topicstarter thinks different about that.
Wants to know how it works.

[travelin texans]

I'm thinking after all these years I need to go back to school & take a 6 week course in "Tire Inflations 101"!! Never realized squirting air into a tire to its recommended pressure was so technical.
Does it matter which knee I kneel on on either side of the rv? I Normally check with gauge, lay it down, using the same hand to hold the air hose, squirt as needed, then use the gauge in that same hand again, repeat at each tire.
SORRY! For that smart a## comment, couldn't help myself!! But that's how these tire discussions seem to go!

[wiredgeorge]

Originally Posted by travelin texans

I'm thinking after all these years I need to go back to school & take a 6 week course in "Tire Inflations 101"!! Never realized squirting air into a tire to its recommended pressure was so technical.

You will need to take a course on barometric pressure, altitude compensation, ambient temperature fluctuation and of course, be able to do in in language no one else can comprehend. Tire inflation is partly art and partly science. Stopping every 3 miles to check pressures may be inconvenient but in three miles altitude, air pressure and temperature can change enough to warrant sitting on the side of the road and adjusting tire pressures.

[travelin texans]

Originally Posted by wiredgeorge

You will need to take a course on barometric pressure, altitude compensation, ambient temperature fluctuation and of course, be able to do in in language no one else can comprehend. Tire inflation is partly art and partly science. Stopping every 3 miles to check pressures may be inconvenient but in three miles altitude, air pressure and temperature can change enough to warrant sitting on the side of the road and adjusting tire pressures.

Well crap!
Then by pulling to the side of the road I'll need to take all the traffic safety courses as well!
WILL IT NEVER END??

[flybouy]

Originally Posted by travelin texans

Well crap!
Then by pulling to the side of the road I'll need to take all the traffic safety courses as well!
WILL IT NEVER END??

I hope you have all your DOT certifications for flag waving and directing traffic! Here's what I do, I inflate my E rated tires to 80 psi. I don't look at NOTAMS ( notice to airman). Check the marine forescat, or consult will "Billy Nye" the science guy or go on NASA's website first. I have an air hose with a regulator, air pressure Guage, and screw on shrader valve attachment. Set the regulator to 80 psi, attach to tire valve and walk away. Come back and move to another tire IF NEEDED. The ONLY time I've had to add air was when there was a slow leak from a tire valve.

My TPMS is close enough for me. I had no idea that I've been doing it wrong for all these years. For the record, I leave chasing windmills to Don Quixote and chasing incremental tire pressures to NASCAR pit crews.

[Tireman9]

Originally Posted by P & T

I asked this question on another thread but I now have some extra TH related questions:

"Where is the best place to get trailer tire inflation "best practices "?

I've been watching my TPMS and have been adding air (and bleeding air) frequently to maintain the 110 psi on the sticker. Always when the tires are cold but how much should I worry about the sunny side vs. the shady side. Ambient is ambient.

Yellowstone park this morning was about 50 deg F ambient at 8am. My shady side was about 103 psi cold-average. Sunny side was 108 psi cold-average. I pumped up everything to 110 psi. Got to Idaho and dropped about 1500 feet in elevation. Now my shady side (from the morning that was ~103 psi) was 115 psi cold-average and the other side was at 108 psi cold-average. Is my "shady side from the morning" over inflated? I bled the air to match the 108 psi and will recheck in the morning.

Sailun 235/80 R16G tires. I use a handheld digital gauge to compare to the TPMS. This is going to drive me batty and I'm probably overthinking things. Thanks in advance."

This morning at 58 deg F ambient (and no sun on any tires), my TPMS is reading 100-102 psi and 48-50 deg F.

Is this where I should leave it alone?
Yesterday my shady driver side is what I inflated but going down the road those tires were running 8-10 psi higher than the passenger side, which is what prompted me to bleed off last night. Driver side was about 128 psi going down the road while the passenger side was 120 psi-ish.

I'm 1500 feet lower today. Is it good practice to adjust to the stickered 110 psi every 1000 '? 2000'? 4000'?

I need a full water tank for today so all of these readings are with the fresh tank full while grays and blacks are empty. My loads are distributed in the TH but do I consider any additional compensations on air pressure when I put a 1600lb toy in the garage? I see a lot of previous posts and tire charts on 2 axle conversations but not 3 axle.

I'll start with these questions and thanks in advance!

1 Stop messing with your tires every day. You are not gaining anything but are potennally damaging the valve core so it might stick and leak,


2 Your standard set inflation can be calculated from your truck scale weight readings and the load inflation tables as long as the inflation needed to carry the measured load is at least 10% below your set pressure.


3. You do not need to adjust for altitude. I covered this in my blog and at most it's only worth a couple PSI.


4. DO NOT BLEED air out of a hot tire. Only set the tires when they are not warmed up from being in the Sun or from driving.


5. You are way overthinking inflation. Just have 10% "cushion" of inflation above the number from the tables and set when tires are not in Sun and are not warm from driving. DO NOT WORRY about Sun side vs Shade side numbers while driving.


6 ONLY worry about being lower than the number in the Load/Inflation table. You can see +20 to +25% increase in hot pressure over cold pressure and all is still OK.