Tires/pressures/temperatures

[dentmac]

And perhaps nitrogen.

Points for discussion....

Interesting topic.
Consider:
On a cool morning (30 ) check and adjust pressure to eg 110 psi.
The day warms to 70 while on the road. The tire pressure goes to 130. Do you adjust? If you leave it and go south it will go to ~134+ .
If your required cold pressure is 120 then the tire will hit 144+psi .
You can't start off underinflated-- tire damage.

TPMS is a safety essential. Some have temp readings. While they are not very accurate, they are surprising.

[folivier]

I haven't found anyone who can answer that question. I usually don't add air on a cold morning if I know the ambient temperature will increase while I'm driving and all of my tires are the same. What is worse: low pressure on a cold morning? Or high pressure once it warms up?
Your tires will warm up in a few miles and your pressure will warm up.
The same thing occurs if you check your tires and the sun is shining on one side. There can be a 5 psi difference between the sunny side and shaded side.

[dentmac]

Agreed-- no one really answers the question and the sunny side can be 5 psi more.
Here is an interesting article describing the dangers , but still no solution.
Obviously, tires 20 PSI over "Maximum tire pressure" is a concern.

Temp and Tire pressures

[davidbrady]

I once read something by a tire professional recommending once per day morning tire pressure adjustments and that should be a good compromise for the typical days journey. Me... I routinely vent air during the day if I think the pressures are high. I never add air during the day unless I know the tire is cold. I don't recommend this to anyone else but I'm comfortable doing it on my bus.

[dentmac]

Venting is reasonable IF the tire is aired UP in the morning to minimal load requirement, Then vented after an hour. But realistically ? Not done.
In a perfect world, the tire should carry the load at 105 cold, then 125- 130 is not a big safety concern, just rough.
Nitrogen could help pressure rise -- Anyone have Nitrogen and TPMS?

[davidbrady]

I think Ron Rueckwald did a medium term study on nitrogen.

Bleeding is frought with the danger of running under inflated if you then drive into colder climates. With experience I've been able to do it. I know how much my tires typically heat up and I know the typical pressure rise when hot. I also know that I can run at a degree of underinflation without carcass damage; although, I acknowledge that I might be shortening the life of the tire a smidge, but I also tend to replace my tires way before their technical expiration date.

[rrueckwald]

Truckers running north and south in the winter encounter this all the time. They must have an established practice. Anybody know it?

[mrkane]

See:
<http://www.bridgestonetrucktires.com/publications/02v7iss1/ra8.asp>

While running, the pressure increase is chiefly controlled by friction with the road and the flexing of the tire raising the internal temperature, not ambient conditions. Tires and wheels are designed to handle the higher pressures resulting from the 'working', when starting from the proper cold setting. Insufficient air pressure results in excessively high temperatures, which result in failures from damage to the tire structure.

I never change the air pressure during a days running, if it was set properly for 'cold' conditions. That is, after having been parked at least 3 hours and before moving more than one mile.

However, I do monitor the tire, wheel, and hub temperatures with a non-contact IR thermometer at each roadside break, (typically every 1.5 hours for Mena.)

M.R.Kane
1987 PT40 'Sleipnir'
currently near Livingston, TX

[JD33]

(11-30-2013 22:46)rrueckwald Wrote:  Truckers running north and south in the winter encounter this all the time. They must have an established practice. Anybody know it?

Yes, the practice is to follow the tire manufacturer when they tell us the recommended cold air pressure. We fill the tire to that pressure cold and do not add or remove air when hot. I am fairly certain that tire manufacturers understand the principals and dynamics of heat on air pressure and that is why they quote a COLD inflation figure only.
We run a truck fleet with over 200 Michelin tires back and forth from Canada to the southern US this way every day without issue or without letting air out of the tires

[rrueckwald]

Thank you, Jim. (Hey I am originally from London, ON)

So what you are saying is to set the pressure when the tires are cold (normal), and if you go to cold climates, set the pressure when the tire is cold in the cold climate and let it ride when you go south. That prevents underinflation when going back to cold climates from hot, but one must be diligent the first time going into a cold climate. Makes sense. The only concern then is whether the tire will get overpressured in hot climates, but you have addressed that. Appreciate your knowledge. I have wondered about the pressure issue for a long time.