Tire Inflation
Proper tire inflation will mean you get
the most from your tires in terms of ride, control, and wear.
There is a maximum pressure marked on the tire. This is
the most pressure you can put in the tire while it is cold,
meaning it has not been moving. As a tire moves, the
flexing of the tire body will generate heat and cause the tire
pressure to rise. The maximum pressure rating has taken
this calculated into consideration.
Tire pressure should always be set when
the tires are cold. You should not adjust the tire
pressure when they are hot. If you check the tires when
they are not cold, you will actually be setting the pressure too
low.
You do have to fill your tires to maximum
rated pressure. You need to fill them to a pressure at
least the value needed for the load on the tire. This
value is determined when you have your
RV weighed. Once
you know the loading of your tires, then you can consult the
inflation guide for your brand of tire.
Here is a sample inflation guide.
You start with your tire size, for example LT235/85R16.
This means you have a 16" rim, the tire tread width is 235
millimeters, and the height of the tread from the rim is 85% of
the 235 mm.
Then you follow the Single (S) or Dual (D)
row. Tires in dual configurations have lower ratings to
insure the tires do not rub on each other.
For our LT235/85R16 example, we have a
tire load of 2900 lbs. You will find that a tire pressure
of 75 psi will give you a tire capacity of 2905 lb. You
will also see that you are in the Load Rate (E). Load
Range (E) tires have a maximum pressure of 80 psi and a tire
capacity of 3042 lbs for a LT235/85R16.
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Here are some Inflation tables:
Goodyear
Michelin
Toyo
*couldn't find Bridgestone or Firestone tables |
From our example you see that 75 psi will
provide the tire capacity you need for your load and be under the
maximum. The tire will ride a little better than at
maximum pressure.
Here are the effects of proper, over and
under inflation.
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Tire Profile
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Proper tire inflation
With proper tire inflation, the air pressure causes
the entire tread contact area to touch the road.
The air pressure matches the weight on the tire
and the tire has flexibility without generating
extra heat. |
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Over Inflation
When a tire is overinflated, the amount of air
pressure exceeds the amount necessary to hold the
weight on the tire. The extra air pressure
causes the tread to bulge downward in the center of
the tread.
In this condition, the weight on the tire is being
carried by a small patch in the center of the
tread. This means there is less road traction
from the tread.
Also, the extra pressure means the tire is not as
flexible as with proper inflation, resulting in a
harder ride. |
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Under Inflation
Under inflation is the worst condition for a tire.
There is not enough air pressure to hold the weight
on the tire. The result is the center of the
tread buckles upward.
With the center of the tread not touching, or
lightly touching the road, there is flexing in the
tire sidewall because of the tread not touching the
road flat. This causes heat from the flexing
which can lead to tire failure.
When the tread is not touching the road flat, the
road traction is reduced. Also, in the
underinflated state, the tire will tend to squirm on
the road, adding more heat. |
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