RE: [VAL] Tires

["Forrest McClure" <forrest@xxxxxxxxxxxxxxxxx>]

All,

For what its worth here is a post from a member of Airstreamforums. I have
used his method of determining the ideal tire pressure on my own trailer and
feel that it works quite well.

"The Real Answer to Tire Pressure"
"I worked for Michelin Tire Corporation for 7 years and Yokohama Tire
Corporation for 11 years. I have given numerous tire seminars on tire
maintenance and especially how to determine the correct tire pressures. So
here goes."
"The pressure on the sidewall of the tire is the maximum pressure at the
published load at approximately 55 mph. (The speed can vary somewhat but it
is not important for our discussion)."
"The air pressure is required to support the load that the tire must carry
in such a manner that the tire flexes at the designed place on the sidewall
of the tire."
"If the load on the tire changes then the air pressure should change
accordingly to keep the tire flexing at the proper place."
"The reason for correct air pressure is to prevent the tire from
overheating. It was put together with heat and it will come apart the same
way. An under inflated tire will eventually self destruct due to excessive
heat build up. An over inflated tire will ride harshly and be more likely to
burst upon impact. Sorry for the long explanation but here is the bottom
line.
To determine the correct air pressure, check the pressure when the tire is
cold. Run the tire for several miles at highway speed. Stop and immediately
check the air pressue in the tire. It should be higher than we cold but no
more than 10% higher.
Now here is the hard to believe part. If the pressure is more than 10%
higher you must ADD AIR and test again. For example if you start with 50 psi
cold. If the pressure is 60 when hot, you have exceeded the (10%) in this
case, 55 psi maximum safe heat build up pressure. You must ADD AIR. In this
case I would add 5 psi which would take the tire to 65 psi when hot. After
you run the tire again you will find the pressure to actually drop because
the tire will run cooler. The heat build up causes the tire pressure to
increase when under inflated."
"On the other hand, if the 50 psi cold pressure does not change when hot.
You have more air than needed. You can remove 5 psi or so and test again
when they return to cold. Like the next trip you take."
"So a fully loaded rig will require more air in the tires than one with
empty tanks and a light load on board. Always error on the side of over
inflation. Thus the maximum sidewall pressure indicated on the tire is
usually used. It usually is more than needed. Each axle has its own
requirement based upon the load on that axle."

Written by "AccessMaster" on Airstreamforums.com 04-11-2003, 10:11 AM


Forrest