Michelin books and Goodyear web page agree on tire pressure verses load on
these tires. Michelin book recommends measuring the load on each tire
individually for a fully loaded RV and then "For control of your RV, it is
critical that the tire pressures be the same across an axle". To me, that
means measuring the full GMC on each front wheel and both back wheels as a
set and determining what the correct pressure should be from the chart on
that set of axles. So you should wind up with two different tires pressures,
one for the front axial and one for the rear axials.
They also recommend a calibrated dual end gage.
The cold inflation tire pressures verses the loads for single LT225/75R16:
35psi/1500 lbs
40psi/1650 lbs
45psi/1790 lbs
50psi/1940lbs
55psi/2060lbs
60psi/2190lbs
65psi/2335lbs
70psi/2440lbs
75psi/2560lbs
80psi/2680lbs
They also recommend increasing the recommended tire pressure by 5 psi "to
accommodate temporary shifting of load from side to side which is common in
RV's".
"A tire that is underinflated will build up excessive heat that may go
beyond the prescribed limits of endurance of the rubber and the radial
cords. This could result in sudden tire failure. A tire that is
underinflated will also cause poor vehicle handling, rapid and/or irregular
tire wear, and an increase in rolling resistance which results in a
decreased in its fuel economy."
"Overinflation will reduce the tire's footprint or contact patch with the
road, thus reducing the traction, breaking capacity and handling of the
vehicle. A tire that is overinflated for the load that it is carrying will
also contribute to a harsh ride, uneven tire wear, and will be more
susceptible to impact damage."
Lowering tire pressures to match their load on our light 23' was the
cheapest and fastest way to cut down on darting in wheel ruts.
Year of manufacture is currently the last three numbers of the DOT number
system. The first two numbers are the week of the year and the last number
is the year. That will be changed in the future to a four number system with
the first two numbers being the week of the year and the last two being the
year. "In cooler, clean air locations, the expected tire life will be
longer than in high temperature, high ozone areas".
Hope this information clears the air on what is the correct tire pressure
for your GMC. I know mine not only rides better, but is a lot less sensitive
to road ruts with the tire pressure lowered to match the tire load + 5 psi.
these tires. Michelin book recommends measuring the load on each tire
individually for a fully loaded RV and then "For control of your RV, it is
critical that the tire pressures be the same across an axle". To me, that
means measuring the full GMC on each front wheel and both back wheels as a
set and determining what the correct pressure should be from the chart on
that set of axles. So you should wind up with two different tires pressures,
one for the front axial and one for the rear axials.
They also recommend a calibrated dual end gage.
The cold inflation tire pressures verses the loads for single LT225/75R16:
35psi/1500 lbs
40psi/1650 lbs
45psi/1790 lbs
50psi/1940lbs
55psi/2060lbs
60psi/2190lbs
65psi/2335lbs
70psi/2440lbs
75psi/2560lbs
80psi/2680lbs
They also recommend increasing the recommended tire pressure by 5 psi "to
accommodate temporary shifting of load from side to side which is common in
RV's".
"A tire that is underinflated will build up excessive heat that may go
beyond the prescribed limits of endurance of the rubber and the radial
cords. This could result in sudden tire failure. A tire that is
underinflated will also cause poor vehicle handling, rapid and/or irregular
tire wear, and an increase in rolling resistance which results in a
decreased in its fuel economy."
"Overinflation will reduce the tire's footprint or contact patch with the
road, thus reducing the traction, breaking capacity and handling of the
vehicle. A tire that is overinflated for the load that it is carrying will
also contribute to a harsh ride, uneven tire wear, and will be more
susceptible to impact damage."
Lowering tire pressures to match their load on our light 23' was the
cheapest and fastest way to cut down on darting in wheel ruts.
Year of manufacture is currently the last three numbers of the DOT number
system. The first two numbers are the week of the year and the last number
is the year. That will be changed in the future to a four number system with
the first two numbers being the week of the year and the last two being the
year. "In cooler, clean air locations, the expected tire life will be
longer than in high temperature, high ozone areas".
Hope this information clears the air on what is the correct tire pressure
for your GMC. I know mine not only rides better, but is a lot less sensitive
to road ruts with the tire pressure lowered to match the tire load + 5 psi.
