Go Back   iRV2 Forums > MOTORHOME FORUMS > Class A Motorhome Discussions
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 10-15-2016, 07:21 PM   #1
Member
 
FatChance's Avatar
 
Join Date: Mar 2015
Posts: 80
What temperature is cold tire pressure based on?

I understand how ambient temperature affects cold tire pressure, but what temperature is cold tire recommended pressure based upon? I type this in SW Colorado where it will vary from the upper 30s tonight to the mid 70s tomorrow afternoon.
__________________

__________________
'04 Newmar Mountain Aire 4016
400ISL/Freightliner
FatChance is online now   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 10-15-2016, 07:34 PM   #2
Senior Member
 
Lv2Roam2's Avatar


 
Winnebago Owners Club
Freightliner Owners Club
Join Date: Jun 2014
Location: Somewhere On the Road
Posts: 335
I use 68 - 70 F as a baseline temp - a few degrees one way or the other doesn't matter if the tire are 'cold' ...
__________________

__________________
Steve
2015 Itasca Ellipse | 2014 Jeep Grand Cherokee
Lv2Roam2 is online now   Reply With Quote
Old 10-15-2016, 08:16 PM   #3
Senior Member
 
bill06447's Avatar
 
Join Date: Mar 2016
Posts: 215
From my days at the Goodyear commercial tire training classes, cold inflation is when the tire has remained idle for a minimum of four hours. It will change with temperature, hence the importance of checking pressures regularly.
__________________
Bill
1991 Winnebago Warrior 23EC Class A
bill06447 is online now   Reply With Quote
Old 10-15-2016, 09:59 PM   #4
Senior Member
 
Polyian's Avatar
 
Join Date: Apr 2014
Location: Victoria, BC
Posts: 162
Ambient air temperature...not driven for at least an hour
__________________
2013 Newmar BayStar Sport 2901
Toad: 2002 Acura MDX Touring
Polyian is offline   Reply With Quote
Old 10-16-2016, 12:00 AM   #5
Senior Member
 
sdennislee's Avatar


 
Monaco Owners Club
Winnebago Owners Club
Join Date: Sep 2011
Posts: 6,404
https://en.wikipedia.org/wiki/Cold_inflation_pressure

Tire Tech Information - Air Pressure, Temperature Fluctuations
__________________
US Navy Vet, Liberty Tree Member of Oath Keepers, NRA & VFW Life Member, Alaska EMT.
2009 Safari Cheetah 40 SKQ
2009 Winnebago Chalet 231CR
sdennislee is offline   Reply With Quote
Old 10-16-2016, 01:28 AM   #6
Senior Member
 
SuperGewl's Avatar
 
Winnebago Owners Club
Ford Super Duty Owner
Join Date: Aug 2004
Location: Oregon
Posts: 1,387
Check the pressure first thing in the morning before being driven(cold) If the sun has risen and is shinning on one side of the MH for a few hours then that side will be somewhat higher in pressure, maybe 1-3 degrees. You can verify this by checking the next day before the sun come up or wait until the sun has passed over to the other side in the evening, as long as the MH has not been driven.
Personally first thing in the morning works best for me due to walking the dog.
__________________
Retired Navy Submariner
2014 Itasca Sunstar 35F; 5 Star tuned; 2014 Jeep Cherokee TrailHawk
SuperGewl is offline   Reply With Quote
Old 10-16-2016, 06:22 AM   #7
Senior Member
 
Waiter21's Avatar
 
Forest River Owners Club
Ford Super Duty Owner
Join Date: Nov 2014
Location: Toledo, OH
Posts: 1,669
I assume it doesn't make a difference what the cold temperature is, the minimum pressure should be as stated.

i.e. If I'm operating in Iowa, and the temperature is -20, when I check my tires in the morning when the tires are cold (we haven't rolled on the tires in several hours), I should have a minimum of 70psi.

When I'm in Airzona, and the air temperature is 115, same dela, when I check my tires in the morning when they are cold, I should have a minimum of 70psi.
__________________
2001 Coachmen Mirada (Ford F53 6.8L V10) - Toad 2003 Saturn Vue.
It won't do MACH 2, but I can get a sandwich and take a pee.
Waiter21 is offline   Reply With Quote
Old 10-16-2016, 06:34 AM   #8
Senior Member
 
Polyian's Avatar
 
Join Date: Apr 2014
Location: Victoria, BC
Posts: 162
Quote:
Originally Posted by Waiter21 View Post
I assume it doesn't make a difference what the cold temperature is, the minimum pressure should be as stated.

i.e. If I'm operating in Iowa, and the temperature is -20, when I check my tires in the morning when the tires are cold (we haven't rolled on the tires in several hours), I should have a minimum of 70psi.

When I'm in Airzona, and the air temperature is 115, same dela, when I check my tires in the morning when they are cold, I should have a minimum of 70psi.
Correct...it's important to check tire pressure regularly, particularly when travelling into different geographical areas. Pressures change with ambient temperature as well as with altitude.
__________________
2013 Newmar BayStar Sport 2901
Toad: 2002 Acura MDX Touring
Polyian is offline   Reply With Quote
Old 10-16-2016, 10:20 AM   #9
Moderator Emeritus
 
Gary RVRoamer's Avatar


 
Fleetwood Owners Club
Freightliner Owners Club
Join Date: Jan 2000
Location: Silver Springs, FL. USA
Posts: 16,610
It's not based on any specific temperature. "Cold" means not driven on in the last 3-4 hours.

The required pressure is stated independent of what the ambient is, i.e. use the same psi whether the ambient if 0 or 80.
__________________
Gary Brinck
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL
Gary RVRoamer is offline   Reply With Quote
Old 10-16-2016, 10:29 AM   #10
Senior Member
 
Polyian's Avatar
 
Join Date: Apr 2014
Location: Victoria, BC
Posts: 162
Quote:
Originally Posted by Gary RVRoamer View Post
It's not based on any specific temperature. "Cold" means not driven on in the last 3-4 hours.

The required pressure is stated independent of what the ambient is, i.e. use the same psi whether the ambient if 0 or 80.
Correct, use the same pressure regardless of ambient temp, but pressure changes with ambient temp. If you check tires at 80F and drive to a 32F location you will find your pressure has dropped:
https://corporate.goodyear.com/en-US...100392863.html

If you drive from Sea Level to 5000 ft you will also see a pressure drop: Tire Tech Information - The Influence of Altitude Changes on Tire Pressure
__________________
2013 Newmar BayStar Sport 2901
Toad: 2002 Acura MDX Touring
Polyian is offline   Reply With Quote
Old 10-16-2016, 10:35 AM   #11
Senior Member
 
Lv2Roam2's Avatar


 
Winnebago Owners Club
Freightliner Owners Club
Join Date: Jun 2014
Location: Somewhere On the Road
Posts: 335
Just as an observation: With our 40K weight I set my pressures at about 70 ambient - 120 lbs steer and 90 lbs drive and tag. Using my TPMS, I check starting pressures and temps every driving day.

In ambients from ~ 50 - 100 my pressures are within 1 - 2 lbs of set. In ambients of less than 45 my pressures are 4 - 5 lbs below set. In all driving conditions, no matter the starting pressures / temps, the pressures rise ~ 10 - 12% from set, and the temps increase ~ 5 - 8 degrees from ambient.

Appreciate others sharing similar info ... thanks
__________________
Steve
2015 Itasca Ellipse | 2014 Jeep Grand Cherokee
Lv2Roam2 is online now   Reply With Quote
Old 10-16-2016, 11:49 AM   #12
Senior Member
 
Coma's Avatar
 
Monaco Owners Club
Join Date: Nov 2010
Location: The Emerald Coast
Posts: 1,745
I have had the same question. On some cars and motorcycle it is specified. 68F for the vehicle I own. This is what I have discovered;

Tire pressure for a vehicle is set by the manufacturer of the vehicle. It is done with guidance from the tire manufacturer. The pressure is picked so as to carry the weight, of course, but also to help the tire get to its operating temperature. At operating temperature the rubber has the right consistency to get the proper friction for braking. Additionly the right pressure gives the tire the correct sidewall stiffness so it contributes not only to the ride but for steering response. In order for the desired characteristics to be present then the tire pressure is referenced to a temperature. This results in the correct pressure for the tire to be higher when warm and lower when cold. Why? When hot you want less squirm in the tire so it doesn't over heat and conversely for colder temperatures you want more squirm so the tire warms up. Naturally you have to stay between the lowest pressure for your weight and the highest pressure permitted by the tire.

With that as background, under inflation which produces overheating is the biggest risk. So make sure the tire is inflated to the pressure, plus 3% for gauge accuracy, that will carry its weight at the minimum temperature for the day. Any additional pressure you add Goes to ride quality, tire stiffness. Checking tire pressure should be done daily before you travel, it is imperative to do this when temperature or altitude changes drastically.

IMHO
__________________
Jim and Jennie, Cats=Bittles and Potter, 2000 Dynasty 350 ISC
2013 Silverado 4x4 Towed with R1200GS in bed.
PROV23:4 Do not wear yourself out to get rich; have the wisdom to show restraint.
Coma is online now   Reply With Quote
Old 10-16-2016, 01:56 PM   #13
Senior Member
 
MN_Traveler's Avatar
 
Join Date: Apr 2012
Location: Minneapolis, MN
Posts: 355
Quote:
Originally Posted by Polyian View Post
Correct, use the same pressure regardless of ambient temp, but pressure changes with ambient temp. If you check tires at 80F and drive to a 32F location you will find your pressure has dropped:
https://corporate.goodyear.com/en-US...100392863.html

If you drive from Sea Level to 5000 ft you will also see a pressure drop: Tire Tech Information - The Influence of Altitude Changes on Tire Pressure
I think people make way, way too much of this. The entire point is that a tire (with a given load on it) has a minimum inflation pressure ... whatever the conditions you simply do not want that pressure to drop below that minimum (I am ignoring the upper pressure limit here). The entire assumption behind "cold tire pressure" is the assumption that as you drive the tire pressure will go up from there (due to temperature rise from friction - generally a good assumption). Ambient conditions (mostly local temperature) will affect that validity of assumption. Living in MN have driven from very cold conditions into warm conditions in a single day. One day driving south starting at ~0 degrees I drove into warm conditions that caused an over-pressure conditions in the tires at about 3pm .... even though in the early morning (cold temps) the tire pressures were just fine. The converse has also happened (and here is where I think your answer really comes out): starting the morning in southern Missouri my tire pressures were just fine (5 psi over minimum in fact). Driving north into MN the temperatures dropped to zero degrees. Towards the end of the afternoon, even though I was driving at 60 mph or so, the tire pressures dropped to bare minimum (I barely avoided having to get out and run my compressor at those temperatures). If I had not had that 5 psi overage to start with ... I would have been 5 psi or so under minimum at the end of the day.

These are extreme temperature swings that most of us do not see ... but hopefully it serves the purpose of example. The essence of the point is that for your ambient temperature you want to avoid the tire pressures falling below your minimum, and that the temperature (and thus the pressures in the tires) is typically lowest in the morning (and before you start running the tire). Lower the tire pressures to that minimum when they are hot from running, and you risk a below-minimum pressure when you start the next morning when the tires are even colder. I do not believe making that adjustment when they are warm is any problem at all as long as you check and correct the pressures if/when they cool off (i.e. if you stop for an extended break, or overnight).

(more nerdy answer follows. FWIW (and it wont matter to many of you), I have a doctorate in chemical engineering (so this stuff is right up my wheelhouse - as it would be for especially for a mechanical engineer, and to an extent for may of the sciences). Two things will affect the tire pressure: temperature and local pressure (i.e. altitude). The easiest expression of pressure versus temperature is the "ideal gas law", which simplifying in this case would be (Pressure = [constant]*Temperature). Temperature goes up (either due to friction or rise in local temperaure) and the pressure goes up. Altitude (i.e. local pressure) ... this is way mis-understood. I regret contradicting Ployian, whom I quote at the start of this, but because local pressure goes down as you go up in altitude, the difference in pressure between the inside of the tire and the outside goes up an amount equal to the reduction in atmospheric pressure (this is stated in the linked article if you read it through to the end). But this pressure change for all but the most extreme altitudes is only a couple psi. The effect of temperature is MUCH more significant. We maybe get confused because as you go up in altitude it just gets much colder at night (which makes for lower tire pressures in the morning - but this is just because of the lower temperature, not the altitude per-se. Bottom line: temperature is much more significant that altitude - so ignore altitude and pay attention to local temperature to flag changes in morning tire pressures.

At this risk of making this way too long ... a specific example: on my recent run from Fresno CA to Minneapolis (via Reno, Salt Lake, southern Wyoming, Nebraska, etc: started out in Fresno at 65F with morning tire pressures set at 90psi (85 psi is my minimum). Reno and Salt Lake with altitude maybe 3000-4000 feet and morning temps around 60 my morning tire pressures were around 86 (ok to go). Laramie Wyoming, at 8000 feet (where you would expect raised pressures from altitude alone), but morning temperatures of 48 or so, gave me tire pressures of 80 psi (5 psi below my minimum). I did not correct pressures, but waited for air temperature to rise enough to give me my minimum of 85psi). The next morning, in Nebraska back down to ~2000 feet, morning temps were about 65, and my morning tire pressures were back to 87 or so. (I did not add or remove air to my tires during the entire 5600 mile trip).

Anyway ... this is way too long - hopefully for those who wade through it it helps
__________________
- 2012 Fleetwood Expedition 36M -
MN_Traveler is online now   Reply With Quote
Old 10-16-2016, 02:39 PM   #14
Senior Member
 
Polyian's Avatar
 
Join Date: Apr 2014
Location: Victoria, BC
Posts: 162
Nice write up MN Traveler

I don't have a recommended minimum tire pressure, only the coach manufacturers recommended pressure and the tire manufacturers maximum pressure. I won't tell you what I studied or what I did for a living because it's irrelevant to the discussion. But I do know how to use Google and read information from the Tire experts.

Here is a good write up from Tire Rack:

Winter Tech Information - Air Pressure, Temperature Fluctuations

If you disagree with the tire experts feel free to write to them
__________________

__________________
2013 Newmar BayStar Sport 2901
Toad: 2002 Acura MDX Touring
Polyian 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
TST versus EEZ RV Products Tire Pressure/Temperature Monitor systems. leeines Gear and Product Discussions 50 11-03-2014 02:29 PM
Tire Pressure and Temperature Monitors Phyleaux Class A Motorhome Discussions 3 07-25-2013 02:05 PM
Tire Pressure / Temperature on 2008 Essex Gene & Kaye Newmar Owner's Forum 10 09-10-2007 06:17 PM
Temperature and altitude for checking tire air pressure? LK23 Winnebago Industries Owner's Forum 23 10-22-2006 11:45 AM

» Virginia Campgrounds

Reviews provided by

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 08:20 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.