Packing up at 14 below zero

[rhlvr1]

We started loading the rig yesterday for our journey to the sunshine state. Had to pry open the frozen door and watched steps slowly creep out. The Chevy 8.1 started amazingly quick as well as the Onan 5500 watt gen. Furnace brought it up to 62 in a few hours. Found a jug of RV antifreeze in basement storage was in a semi- solid jel state. Visualized an indoor"sprinkler" system happening at first hook up in Florida. Assuming I can maneuver a 180 degree turn around in my 8" snow covered yard, we will be on our way tomorrow. My question is, if my tires read 70 psi now, what do I pump them up to? I realize I will be checking them at first stop and would like to have them between 95-100 psi.

[rezman]

Tires a checked and adjusted cold. So set them at your normal pressures and drive. If staying south you can recheck them cold one morning and let some air out.

[J Birder]

Originally Posted by rhlvr1

Found a jug of RV antifreeze in basement storage was in a semi- solid jel state. Visualized an indoor"sprinkler" system happening at first hook up in Florida.

Don't worry about it. Water is unique. Iexpands when it freezes, so it breaks pipes. Almost all other liquids (including RV antifreeze) shrink when they freeze and do nor damage pipes.

Joel

[Arch Hoagland]

I always set my tire pressure when the tires are cold with no sun shining on them.

Yours are definitely cold!!!

As rezman said, once you get to warmer country drop the pressure a bit.

What year, make and model RV do you have?

Nice to hear it started quickly at 14 below!

[bdickson]

I found this article on tire pressure vs temperature: Bridgestone Commercial Truck Tires
The key message is that when we talk about "cold" inflation pressure, what they mean is that the temperature of the air inside the tire should be the same as the ambient temperature. So, the OP should inflate his tires to his usual "cold" pressure, and if necessary bleed out some air when he has reached warmer climes.

[Sky_Boss]

I just went through that process but not nearly as extreme as yours. In short we left IL with 25* temps and inflated our tires to the proper cold tire temps of 115/85/75 (front, drive & tag). By the end of the first day as we headed south temps got up into the 50s and my TPMS started giving high pressure warnings on the one front, one drive tire and one of my toad tires.

So the next morning in Clarksville, TN with morning temps of 35* I needed to let out about 7-8 PSI in all my RV tires and 2-3 PSI in my toad tires. This was not unexpected.

The next day we got into Macon, GA with 65* temps and just before we got there I got a high pressure alarm in one of my drive wheels. A couple evenings later with temps about 60* I had to let out about another 5-6 PSI from the RV tires and 2-3 PSI from the toad tires. This was to prep for my next morning departure to FL.

Now, as I sit on the beach in Carrabelle, FL (pan handle south of Tallahassee) the outside temps are 65 and my TPMS is showing all my tire pressures to be about 1 PSI high which ain't a problem at all. HOWEVER...if we were in 75* temps I would suspect I might take out a couple PSI.

NOW...was this hard to do? NOT AT ALL. I hate to sound like and ad man but one of the best tool investments I ever made last year was in the POWERTANK TIG-8300. It has made it very easy to inflate and deflate tires quickly and accurately. It is a bit pricey but for me...worth it. YMMV.

POWERTANK - CO2 Air Systems

I have checked it against 2 truck tire pressure gauges and it seems spot on. My TPMS shows my PSI 0-2 PSI lower than the Powertank gauge does TPMSs do vary a bit anyway. No big deal.

[thrushl]

Originally Posted by Sky_Boss

I just went through that process but not nearly as extreme as yours. In short we left IL with 25* temps and inflated our tires to the proper cold tire temps of 115/85/75 (front, drive & tag). By the end of the first day as we headed south temps got up into the 50s and my TPMS started giving high pressure warnings on the one front, one drive tire and one of my toad tires.

So the next morning in Clarksville, TN with morning temps of 35* I needed to let out about 7-8 PSI in all my RV tires and 2-3 PSI in my toad tires. This was not unexpected.

The next day we got into Macon, GA with 65* temps and just before we got there I got a high pressure alarm in one of my drive wheels. A couple evenings later with temps about 60* I had to let out about another 5-6 PSI from the RV tires and 2-3 PSI from the toad tires. This was to prep for my next morning departure to FL.

Now, as I sit on the beach in Carrabelle, FL (pan handle south of Tallahassee) the outside temps are 65 and my TPMS is showing all my tire pressures to be about 1 PSI high which ain't a problem at all. HOWEVER...if we were in 75* temps I would suspect I might take out a couple PSI.

NOW...was this hard to do? NOT AT ALL. I hate to sound like and ad man but one of the best tool investments I ever made last year was in the POWERTANK TIG-8300. It has made it very easy to inflate and deflate tires quickly and accurately. It is a bit pricey but for me...worth it. YMMV.

POWERTANK - CO2 Air Systems

I have checked it against 2 truck tire pressure gauges and it seems spot on. My TPMS shows my PSI 0-2 PSI lower than the Powertank gauge does TPMSs do vary a bit anyway. No big deal.

I too have the Powertank System and certainly agree that it is not low cost. HOWEVER, it has saved me so many times and as you say, worth the cost TO ME. Certainly it is not for everyone, but nothing is, eh?

[vsheetz]

Originally Posted by Sky_Boss

I just went through that process but not nearly as extreme as yours. In short we left IL with 25* temps and inflated our tires to the proper cold tire temps of 115/85/75 (front, drive & tag). By the end of the first day as we headed south temps got up into the 50s and my TPMS started giving high pressure warnings on the one front, one drive tire and one of my toad tires.

So the next morning in Clarksville, TN with morning temps of 35* I needed to let out about 7-8 PSI in all my RV tires and 2-3 PSI in my toad tires. This was not unexpected.

The next day we got into Macon, GA with 65* temps and just before we got there I got a high pressure alarm in one of my drive wheels. A couple evenings later with temps about 60* I had to let out about another 5-6 PSI from the RV tires and 2-3 PSI from the toad tires. This was to prep for my next morning departure to FL.

Now, as I sit on the beach in Carrabelle, FL (pan handle south of Tallahassee) the outside temps are 65 and my TPMS is showing all my tire pressures to be about 1 PSI high which ain't a problem at all. HOWEVER...if we were in 75* temps I would suspect I might take out a couple PSI.

NOW...was this hard to do? NOT AT ALL. I hate to sound like and ad man but one of the best tool investments I ever made last year was in the POWERTANK TIG-8300. It has made it very easy to inflate and deflate tires quickly and accurately. It is a bit pricey but for me...worth it. YMMV.

POWERTANK - CO2 Air Systems

I have checked it against 2 truck tire pressure gauges and it seems spot on. My TPMS shows my PSI 0-2 PSI lower than the Powertank gauge does TPMSs do vary a bit anyway. No big deal.

I have a CO2 tank as well. Primary usage is airing up the Jeep tires after off-roading. And works great for maintaining the coachntires as well.

[Sky_Boss]

Originally Posted by vsheetz

I have a CO2 tank as well. Primary usage is airing up the Jeep tires after off-roading. And works great for maintaining the coachntires as well.

I don't use any of the CO2 tanks, just the tire pressure gauge. I really like the gauge.

[jadatis]

When the tires are filled at about 65 dgr F at 95 psi , then it will drop even about 10 psi when the outside, so inside-tire temperature cold, is fi 24 degr outside. With that pressure lowering also the deflection of the tire gets more, so you have to use cold pressures that are adviced measured at that cold outside temperature. So fill them up to 95 or 100 psi if thats the advice.

If then the outside temperature rises back to 65 dgr , the cold pressure will rise about 10 psi , so mayby above the pressure given on sidewall, and with that a lesser deflection of tire.
American TRA allows this higher pressure then maxloadpressure up to 10 psi for LT tires and even 20 psi for truck tires.
I once determined from an European article from Semperit ( Continental) , in wich for standing still , 2 times the given maximum load is allowed when the pressure is 1.4 times the maxloadpressure, that the maximum pressure of an LT and truck-tire is 1.4 times maxloadpressure ( cold).
So this shows how far you can savely go for the tires.
Also the valves are designed to stand a higher pressure then given cold.
The temperature can rise up to boiling point of water in the tire, and the valves can stand that temperature and pressure-rising that goes with it.
This boiling point of water it can incidentially get by the heat of the brakes transported trough the rimms.

[jerichorick]

All of this is great stuff except for one thing. The manufactures I have read state that the cold temp psi is figured on an ambient temp of 70*F. With this knowledge I am right back to the beginning of the decision. When it is 20* out and I check my tires what pressure do I use? If I drive 5 hrs and the air temp rises to 70* I can't adjust my tire pressure for an hour according the the manufacture. The tires must stabilize to the air temp to get a correct reading. So, here I sit totally !

Happy trails ,
Rick

[Mac99]

I think you have gotten some bad info, you set your tires when cold
at the correct pressure based on your coach weights. When driving
in big temperature changes and altitude changes, the fluctuations
in pressure are of no consequence. But when driving in these
situations, you really do have to check your pressures every morning
before you take off.

[Sky_Boss]

Originally Posted by macadnphyl

I think you have gotten some bad info, you set your tires when cold
at the correct pressure based on your coach weights. When driving
in big temperature changes and altitude changes, the fluctuations
in pressure are of no consequence. But when driving in these
situations, you really do have to check your pressures every morning
before you take off.

UMMM...I kinda agree and kinda don't. LOL

I think there are some principles that must be considered before saying what I do.

It is pretty clear that there will always be factors that affect tire pressure that are built into the tire pressure charts. I totally agree that it is important to start off the day with the proper pressure based on weight. If a tire needs 110 PSI to support the weight it doesn't matter if it is 20* or 120*. They still need 110 PSI.

Now...here is where I diverge a tad...

If it is 20* @ 7 am and then by 4 pm it is 55* then there will be a significant difference in the tire pressure compared to remaining within a close proximity of 20*. That being said, under what conditions might this require some intelligent/thoughtful adjustments?

Let me start with, IMHO, the biggest factor and that is starting cold PSI relative to max cold PSI. My front wheels need 115 PSI and have a max of 120 PSI. The drive and tag wheels need between 75 & 85 PSI. I don't see any situation where over the course of a day that either the drive or tag wheels will every get over inflated in a manner that can damage the tires. They may run a bit rougher but no damage to be seen. OTOH under some extreme situations I don't feel the same about the front tires. In the case I outlined earlier in this thread, the tire pressures increased so drastically that they cause a few of them to generate over pressure warnings. I use TST's recommendation of 20% over the nominal cold tire pressure needed to support the weight.

Now...I am not so crazy as to get hyper because of an over pressure alarm that is just at or within a couple PSI of my alarm limits. HOWEVER...once I see 4 or more my tires generating that alarm and I have miles to go, I feel the need to take some action. I take that action not only to protect the tires from being over inflated but to take some of the harsh ride generated in the front axle.

Here is what I did after I was up to 4 out of 12 tires giving high pressure alarms.

1. On the front axle I reduced the wheel with an alarm down to the pressure of the one not in alarm.

2. I did the same with the tag wheel.

3. I equalized all drive wheels to the same pressure as the highest wheel not in alarm.

4. On my toad (yes, I had one of those tires alarm) I equalized all four wheels to the highest PSI not causing an alarm.

The next morning I found all tires within 1-2 PSI of each other on and axle by axle basis HOWEVER...they all were about 5-6 PSI too high so I further reduced the pressure back to my target.

I then continued south and in the course of the day got 1 over pressure warning but let it slide since it was the only one and right on the edge of the alarm limits. The next morning I had to further reduce PSI about 5 PSI for ALL tires both RV and toad.

I continued further south to slightly warmer temps but haven't had to re-adjust since.

So...right, wrong or indifferent...when I get multiple over pressure alarms I will take action to fix that. My goal is to reduce PSI to the upper alarm limits and be equal on each end of the axles.

NO! I do NOT ever reset tire PSI back to what they should be when they are cold. THAT would be pretty stupid. I use the upper alarm limit as my guide.

[jadatis]

Originally Posted by jerichorick

All of this is great stuff except for one thing. The manufactures I have read state that the cold temp psi is figured on an ambient temp of 70*F. With this knowledge I am right back to the beginning of the decision. When it is 20* out and I check my tires what pressure do I use? If I drive 5 hrs and the air temp rises to 70* I can't adjust my tire pressure for an hour according the the manufacture. The tires must stabilize to the air temp to get a correct reading. So, here I sit totally !

Happy trails ,
Rick

then read back my post in wich I state that you have to fill them cold at 20 dgr outside temperature then the inside tire temperature and the air you fill them with is also 20 dgr. Then fill at that 95 or 100 you are adviced.
Then if the temperature rises back to 65 dgr F/18 dgr C or what you write 70dgrF/20dgr C the cold pressure , so inside tire temp is same as outside tire, will rise about 10 psi. and if that is above the presssure written on the sidewall wich is also for cold measured, its OK by TRA up to 10 psi for LT tires.
But you need this pressure of 95/100 at 20 psi, to give the tire a deflection so it wont get damaged by the about 10 times a second bending of the rubber, when driving about 55 m/h.

Will include a picture of my pressurecalcationwithtemp spreadsheet , that i used in another topic with that 24 degrees, to show what it can chanche.