Go Back   iRV2 Forums > iRV2.com COMMUNITY FORUMS > iRV2.com General Discussion
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 07-03-2016, 06:44 PM   #1
Member
 
Terry L T's Avatar
 
Monaco Owners Club
Join Date: Mar 2015
Location: Apache Junction, AZ
Posts: 66
Unhappy Elevation VS Tire Pressure

I'm at 3,200' elevation and 70 degrees, getting ready for the next leg of our trip and discover the tires are nearly 10 psi lower cold at this elevation and temp, than they were when we left Arizona at 105 Degrees and 1100' elevation.
My problem is that they are right at the load we now have on them!
I wanted nearly 10 psi fudge factor (safety). If I increased them back to where they were, once I get back to flat land and hotter, they will be nearly 20 pounds too high.
Should I worry about it ??
__________________

__________________
Terry & Linda, 2 dogs Sammy & Ellie Mae 1 cat Martin. '03 Beaver Monterey Newport 39'10" 350 HP with 1050# Torque, Magnum Chassis
Toad, '05 Saturn Vue on dolly
Terry L T is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 07-03-2016, 06:56 PM   #2
Senior Member
 
vsheetz's Avatar


 
Fleetwood Owners Club
Ford Super Duty Owner
Join Date: Jun 2012
Location: SoCal
Posts: 11,789
I would not worry with it...
__________________

__________________
Vince and Susan
2011 Tiffin Phaeton 40QTH (Cummins ISC/Freightliner)
Flat towing a modified 2005 Jeep (Rubicon Wrangler)
Previously a 2002 Fleetwood Pace Arrow 37A and a 1995 Safari Trek 2830.
vsheetz is online now   Reply With Quote
Old 07-03-2016, 07:57 PM   #3
Senior Member
 
Rexhall Owners Group
Join Date: Jul 2013
Location: Beavercreek, OH
Posts: 101
Terry,

Don't know the elevation where you were in AZ, but an increase in altitude will increase the gauge pressure at a rate of 0.5 PSI per 1,000 ft (because the gauge compares the tire to the atmosphere and that atmospheric pressure drops as altitude increases). Temperature changes impact pressure at a rate of about 1% per 5 degrees(in fahrenheit). Cooler means lower pressures. The 45 degree drop in temp for a 100 psi tire would be about 9 PSI and probably accounts for the drop you saw in pressure.

The Tire and Rim Association load and pressure table recommendations assume a pressure at ambient temps. Like you, I typically run the tires about 10% above the minimum pressure for the weight and don't adjust for temp changes unless the pressure change puts me below 105% of the minimum.

Sorry for the tech stuff, but I kinda like to pass along the "back up" for my humble opinion.

Hope your enjoying the cooler weather!
__________________
Jim & Lin
56safari is offline   Reply With Quote
Old 07-04-2016, 12:53 AM   #4
Senior Member
 
MtnTrek's Avatar
 
Join Date: Jul 2015
Location: Currently; SW Cali. Sunny & warm!
Posts: 1,114
interesting topic

Hi,
Thanks for the explanation 56safari.



Happy safe motoring.
Attached Thumbnails
Click image for larger version

Name:	table1.png
Views:	35
Size:	61.1 KB
ID:	131984  
Attached Images
 
__________________
DRV Suites, ES-38RSSA
J & J & Kickr's the Vonderhund
GM Denali, 3500HD-Max, CC, 8'-DRW, 4x4
MtnTrek is offline   Reply With Quote
Old 07-04-2016, 04:06 AM   #5
Senior Member
 
jadatis's Avatar
 
Join Date: Oct 2012
Posts: 247
The altitude would only make a difference of 1 psi higher measured pressure, so the pressure-dropp must be explained only by the temperature drop from 105 to 70 degr F.
I have put it in my made spreadsheet and filling in 120 psi at 105 degr F gave 111.7 psi at 70 degr F
Add 1 psi for altitude ( taken from list MtmTrack gave) would be 112,7 wich is nearly 10 psi lower.

So if your filled pressure was realy that 120 psi , dont worry, but the advice pressures are given for 65 /70 degr F, so fill up to 120 ( if that is true) at the 70 degr F. For 105 degr F they need higher pressure , because this gives lesser deflection so lesser heatproduction , because at that AmbiŽnt temp the cooling down of tire is also less, because of smaller temp-differences.

If your filled pressure is for instance 80 psi at 105 degr, it would only drop to 74.1 + 1 psi for hight= 75.1 so then you must have lost some pressure another way.

Once read that tires are tested to can stand a pressure of 2 to 3 times AT-pressure ( probably your 120 psi), and in PDF of Semperit/Continental I have got they alllow for Truck/tires 1.4 times AT-pressure ( cold) for standing still and it gives about 2 times the maximum load.
So for trucktires the tiremakers allow this higher pressure ( up to max of10 bar/145psi is the border they give to where you can do this)

Also for normal car tires with AT pressure of 35 psi , they only give maximum cold pressure on sidewall of 44 to 51 psi , depending on brand, so also allowed to go over AT-pressure.

And even American tiremakers did allow in the past a 10 psi extra above AT-pressure, but nowadays not anymore ( ???).

But I have contacted by mail 3 European tiremakers ( Michelin, Continental and Vredestein/Apollo) and they dont allow it for C- tires ( European LT tires). Still busy figuring out why not for LT and allowed for P-tires and Truck-tires.
think its a marketing thing, because in Europe where I live , some tiremakers have CP tires especially for Motorhomes wich give 80 psi maximum cold pressure , while they are 8 Plyrated ( EUR for D-load) with AT pressure 70 psi. Continental even writes both at the sidewall , maximum cold pressure of 80 psi and something like "maximum load xxxx kg/lbs AT 69 psi( cold) ".
If C/LT tires 8 PR would be allowed the 80 psi , people would not buy the CP tires.

So now I will suggest to them , if its allowed to fill at freesing point of water ( zero degr C, 32 degr F) the 65 or 70 psi AT - pressure and it will rise to 71/76.4 psi when 68 degr F , do I need to let of air then or can I stay ath the 71/76.4 at that temp , though its higher then the AT - pressure , wich they write they dont allow.
A trick to fill higher pressure and still be in the clear with the tiremakers.

In Europe ( Holland) where I live there are a lot of Motorhomes with GAWR of 7700 lbs/3500 kg, because they are allowed to be driven with Driverslicence B , wich most only have, and the newer ones sometimes weigh about 3000 kg/6600 lbs empty , so often overloaded and this overload is because of the build of motorhomes only on Rear axle.
E- load tires are not that often found in the sises here in Europe, so we have to do with D-load/8PR tires and because of that the tires maximum load together are yust enaugh for the GAWR.

So this is the reason why I want that higher pressure then AT, for rear , to cover overloading ( tiremakers dont support higher then maximum load at that higher pressure , but laws of nature do). And in fact for the CP tires they advice 80 psi for rear, Michelin wrote me its to cover Peakloads, wich I translate as to be expected ( but not allowed by law) overloading.
Gives that extra reserve , so lesser heatproduction, so lesser chanche on damage to tires wich can lead to tire failure and blowing tires.
__________________
jadatis is offline   Reply With Quote
Old 07-04-2016, 10:41 PM   #6
Senior Member
 
Ray,IN's Avatar
 
Join Date: Aug 2001
Location: North America somewhere
Posts: 13,699
Quote:
Originally Posted by Terry L T View Post
I'm at 3,200' elevation and 70 degrees, getting ready for the next leg of our trip and discover the tires are nearly 10 psi lower cold at this elevation and temp, than they were when we left Arizona at 105 Degrees and 1100' elevation.
My problem is that they are right at the load we now have on them!
I wanted nearly 10 psi fudge factor (safety). If I increased them back to where they were, once I get back to flat land and hotter, they will be nearly 20 pounds too high.
Should I worry about it ??
Nope. you only concerns are not to exceed sidewall listed pressure or run below load/inflation chart minimum listed pressure.
Some folks mistakenly run lower air pressure in the belief they will obtain a smoother ride; NOT SO, according to Michelin,Goodyear, Firestone, RMA=Rubber Manufacturers Assn.
__________________
2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member,FMCA."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert the Constitution. "Abraham Lincoln"
Ray,IN is offline   Reply With Quote
Old 07-05-2016, 07:31 PM   #7
Moderator Emeritus
 
Gary RVRoamer's Avatar


 
Join Date: Jan 2000
Location: Silver Springs, FL. USA
Posts: 18,073
No worries. You are within the range of your safety margin, which exactly why you over-inflated about 10 psi to begin with. When you go back down, you get your margin back. The only time to worry would be if you expected to go to an even colder level, which might put you under the minimum.

If you were staying weeks or months at that level, it would be worth adjusting the pressure to the new ambient, but if you plan to return to your previous "normal" soon, I would leave it alone.
__________________
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
Gary RVRoamer is offline   Reply With Quote
Old 07-06-2016, 01:56 PM   #8
Senior Member
 
Glenn and Kathy's Avatar
 
National RV Owners Club
Workhorse Chassis Owner
Join Date: May 2000
Location: California Central Coast
Posts: 1,200
I don't see any real change in pressure from altitude change. I set my pressure at 95# steer and 90# duals at 4800' before I leave for the river. When ready to leave the Colorado river at about 400' altitude The pressures still read 95 and 90# when I check them. It is also 10 to 15į warmer at the river.

Glenn
__________________
2006 Sea Breeze LX 8341 on a Workhorse W22 Chassis with 22.5 Alcoa Alum wheels,
2011 Chevy Colorado 4X4 with Ready Brake
Glenn and Kathy is offline   Reply With Quote
Old 07-06-2016, 04:01 PM   #9
Senior Member
 
Jamie65's Avatar
 
Join Date: Apr 2014
Posts: 234
If you have a TPMS on your coach, you will see that only a few miles down the road the tires will warm up and be back to normal pressure
__________________
Ed & Kathleen
2003 Tiffin Allegro 40'
Jeep Liberty Tow
Jamie65 is offline   Reply With Quote
Old 07-07-2016, 08:21 AM   #10
Senior Member
Commercial Member
 
Join Date: Mar 2010
Location: Akron, Ohio
Posts: 1,471
Ok guys, just way too much overthinking about pressure change. You sound as bad as a Tire Engineer.

I suggest you review my post
Don't get your shorts in a bunch about tire inflation



A key point about tire temperature. If you are looking at the number reported by your TPMS you need figure it is 1. cooler than the tire since the sensor is getting cooled by outside air. 2. TPM do not measure the hottest part of a tire. 3 Air is a good insulator so hot air in a tire is cooler than the air in a valve stem.




Pressure changes about 2% for 10F. I would not worry about change in elevation unless you are on a Moon Rover. Get and use a TPMS.
__________________
Retired Design & Quality Tire Eng. Read my tire blog RVTireSafety.NET to learn more about RV tires, valves & wheels. Read THIS post on why Tires Fail
Tireman9 is offline   Reply With Quote
Old 07-07-2016, 08:26 AM   #11
Senior Member
Commercial Member
 
Join Date: Mar 2010
Location: Akron, Ohio
Posts: 1,471
Quote:
Originally Posted by 56safari View Post
Terry,

Don't know the elevation where you were in AZ, but an increase in altitude will increase the gauge pressure at a rate of 0.5 PSI per 1,000 ft (because the gauge compares the tire to the atmosphere and that atmospheric pressure drops as altitude increases). Temperature changes impact pressure at a rate of about 1% per 5 degrees(in fahrenheit). Cooler means lower pressures. The 45 degree drop in temp for a 100 psi tire would be about 9 PSI and probably accounts for the drop you saw in pressure.

The Tire and Rim Association load and pressure table recommendations assume a pressure at ambient temps. Like you, I typically run the tires about 10% above the minimum pressure for the weight and don't adjust for temp changes unless the pressure change puts me below 105% of the minimum.

Sorry for the tech stuff, but I kinda like to pass along the "back up" for my humble opinion.

Hope your enjoying the cooler weather!
Good Plan. That's what I do too.
__________________

__________________
Retired Design & Quality Tire Eng. Read my tire blog RVTireSafety.NET to learn more about RV tires, valves & wheels. Read THIS post on why Tires Fail
Tireman9 is offline   Reply With Quote
Reply

Tags
tire pressure



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Engines Shuts down with elevation change RandyG26170 Workhorse and Chevrolet Chassis Motorhome Forum 14 05-24-2017 12:41 PM
Winegard digital elevation readout darbyjudy Technology: Internet, TV, Satellite, Cell Phones, etc. 8 01-22-2011 10:33 AM
winegard elevation sensor error Clifftall Technology: Internet, TV, Satellite, Cell Phones, etc. 4 09-27-2010 02:48 PM
Highway Elevation Map varonjill Navigation, Routes & Roads 3 11-26-2009 08:52 AM
Where can I find the elevation of a CG? ncason iRV2.com General Discussion 13 08-11-2006 05:06 PM

» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 09:02 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.