Tire pressure

Hobo · 12-18-2005, 04:16 PM

When traveling cross country I find myself in large temperature changes. Starting in 70 to 75 degrees and wake up the next morning at 40 degrees. My tire pressure has dropped 10lb across the board.
Do I add the 10lb or let it go knowing it will be at lest 70 by noon.

That can also go the other way leaving north country at 35 degrees and the next morning waking to 60+ temperatures where the tire pressure is now 5lb above the max rating. Does one start letting air out?

I cross the country at lest twice a yr east west and north south and have been pondering this a lot lately.
Thank for any input you can give me.
Rick

Motor31 · 12-18-2005, 05:36 PM

Per the same questions asked and answered by a tire rep at a rally this last summer.

Take the pressure cold before the tires rotate or become exposed to direct sunlight and air to the apropriate pressure for the load.

Never let air out during the drive after the tires have heated up if you have followed the above practice.

Pressure changes due to altitude are negligible. Just air the tires according to the load and manufacturers recomendations in compliance with the wheel manufacturers limits.

Hobo · 12-18-2005, 07:07 PM

Motor 31
Ok say I leave TX and the pressure is ok at 70 degrees. The next morning I'm in the mountains of NM and the temp is 40 degrees and the tires read 10lb less, 100lb instead of the 110. I know I will be in South AZ by afternoon in 80 degree temps. Do I add the 10lb before I leave?
Rick

rverdlm · 12-18-2005, 09:26 PM

My answer after a lot of travel; Let them alone! IMHO all these reminders to check your tires are for those who don't travel! There is a lot of tolerance in the recomendations. Our tires increase pressure by 15 PSI from the morning 125 psi and they are still OK. The main thing is to not start out in the morning when your tires are already low.

Cooper · 11-17-2006, 09:14 AM

110 PSI is the max for a tire why would you run the max. If a tire says 110 PSI you should run around 95 PSI that the way I was train and it has always worked for me. Look on the back of your wheel and it will be stamped max PSI and most or 110 PSI and it will show the weight rating also.
If your tires or 10 PSI low when you drive for a few minutes it will warm the tires and raise the PSI.

Motor31 · 11-17-2006, 09:55 AM

You should run the max pressure if the load is at max for the tire. Running 15 PSI under max when you have loaded the tire to it's maximum weight capacity means you have just underinflated it. Per the tire rep, the tire runns coolest when it is not flexing to an excessive degree. Under inflating it means you are allowing the tire sidewalls to flex more than if you are at the maximum pressure listed on the sidewall before you start out.

Hoping your tires warm up enough to bring them up to the proper operating temperature by flexing has just put excessive wear on the sidewalls in the process. That's asking for a premature failure. I trust the folks who designed, tested and manufactured the tire to know their product and operating procedures far more than any one who does not have the credentials or testing procedures on the product.

Inflate the tires when cold to the proper pressure before you start out and leave them alone during the drive other than to make sure they have not lost pressure and are getting hot. Check and adjust as needed cold the next morning before you start out again.

MDTdriver · 11-17-2006, 02:53 PM

I just want to second Motor31, I have met him in Wi. And this is how I have done my tires for as long as I can rember, one class A,three 5er's,two truck campers and 4 wheeling for 25 years in rocks and sand. Air them up or down for your load, in the morning while cool and do not touch them all day, unless you have a leak then you have another problem.

Larry & Kathy plus Meeko