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Hot Weather Operation Considerations
When we refer to hot weather operation, we are referring
to ambient air temperatures greater than 95 degrees farenheit.
The higher the temperature climbs, the greater the importance
of these considerations.
Tire
Considerations
The number one cause of tire failure, is heat. When you run a
tire under inflated, the friction from being low causes damaging
heat generation. The same friction which makes your brakes work,
 destroys
your tires. Bias ply tires are much more susceptible to under
inflation self destruction due to the way the bias ply tire is
constructed. If you have tubes inside the tire, under inflation
causes the tube to work within the tire which causes more heat
generating friction.
If you plan to drive a lot in very hot climates, you should not
consider tire caps. The caps are most susceptible to heat. The
best way to extend tire cap life is to keep them fully inflated
at all times. All of these tire factors are severely aggravated
during hot weather driving.
Radiator Fluid Control
The first most important thing you can do is keep a 50% antifreeze
solution in your radiator. This provides several advantages. First,
it reduces radiator fluid expansion. The antifreeze expands less
at high temperatures than does plain water. The 50/50 solution
also increases the boiling point of the solution, so there is
less chance if boiling fluid from your radiator.
 The
anteater trucks (low front profile) have an additional problem
to consider. Due to the low frontal area of this design, the top
of the radiator is lower than the top of the engine. Water is
added through a reservoir recovery tank. With this design, any
time the radiator gets a little low on fluid, then the cylinder
heads of the engine have no cooling water.
The recovery tank is there to hold the expanded hot water. If
the recovery system is not working properly, expanded water is
not recovered when the engine cools off. Using antifreeze reduces
the expansion problem, which reduces the possibility of boiling
out the radiator fluid.
Bugs Amongst Us
It is surprising how many trucks run around with large quantities
of bugs caked onto the radiator fins. The little critters interfere
with air flow around the radiator fins, and can have a pronounced
impact upon engine cooling temperature rise. The easiest way to
control the bugs is to place some window screen in front of the
radiator, and simply replace the screen once it has collected
a sufficient number of critters.
Fast Idle
If you leave your engine idling for extended periods, it is recommended
by the engine manufacturers to increase the idle speed to 1000
- 1200 RPM. The fuel injection systems are not efficient at idle
speed, so that excess fuel causes carbon buildup inside the engine.
Most of the newer E-engine trucks with cruise control have a feature
to advance the idle speed of the engine. The older models usually
offer a dash controlled engine speed setting.
Braking Considerations
Your brakes work because of heat generating friction. The hotter
the ambient air temperature, the longer it takes your brakes to
dissipate the braking generated heat build up of the brake shoes
and drums. During hot weather operation, you should avoid lengthy
light brake applications. Use
shorter and heavier braking, road conditions permitting, because
that reduces the prolonged heat build up of long term light braking.
The greater the temperature difference between two substances,
the greater the heat transfer characteristics. When you do short
hard braking, the increased brake drum temperature will dissipate
heat to the ambient air faster than the lower temperature generated
by prolonged light braking. Reduction of vehicle speed takes a
certain amount of energy. The harder you brake, the more peaked
is the energy braking temperature, therefore the greater the heat
transfer away from the brake drums.
Road surface should always be factored into braking pressures.
With rain soaked road surfaces, you obviously can not perform
peaked braking, and must resort to less braking pressure for a
longer time.
We have noticed that some of the newer trucks don't have a trailer
brake handle. One situation where we think this is dangerous,
is when the tractor-trailer entesr into a curve with to much speed.
Some times the driver is caught unaware, and finds the speed to
be excessive for the curve. In this situation, heavy braking pressure
could put you into a jackknife without a trailer brake handle.
When centrifugal forces are already heavy, the addition of heavy
braking will result in a vector pushing force of the trailer which
will add to the centrifugal force, which will increase your problem
situation. Use of the trailer brake handle alone, helps to prevent
the jackknife in this situation. If you are driving without a
trailer brake handle, you had better pay more attention to your
entry into curves!
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