The Victoria Napolitano Bookstore THE DRIVING COMPANY WORKBOOK | Page 29

Tires
TIRES
A lower tire pressure off-road than when
on-road is very beneficial. When you low-
er the tire pressure, you increase the con-
tact patch, or that portion of the tire in
contact with the ground. The exact tire
pressure depends on the type of driving
surface. Tire pressure of 30–35 lb. works
well for stock emergency vehicles for most
applications. This will allow you to travel
at average speeds on-road and transition
to off-road with little difficulty. If you are
operating in sand, mud, or snow, it will be
much lower. Tire pressure is dependent on
your type of vehicle, type of tires, the envi-
ronment in which you are driving, and the
nature of your assignment. For recreation-
al off-roaders, you can air-down to the best
off-road pressure for the environment you
are in and then simply air-up when you are
done. Emergency responders need to find
a pressure that allows decent off-road and
on-road performance as they may be tran-
sitioning between the two.
Be careful to not get too much lateral force
on tires with very low pressure because you
risk running the tire off the bead. It will go
completely flat and it is very difficult to get
it back on the bead.
Do not air-down dual wheels because the
sidewalls will rub together causing tire
damage. Some people have tried to air-
down dual wheels but only to the point
just before they touch. The problem with
that is when the vehicle goes over bumps,
the tires will flex, causing the sidewalls to
touch.
SAFETY NOTE: Low tire pressure on-
road will result in higher friction, which re-
sults in higher tire temperature. Tire failure
is more likely when the tires are running
hot. Do not try to “performance drive”
any SUV. These vehicles are not designed
for high-speed performance driving. At-
tempting to performance drive a vehicle
on-road with improperly inflated tires can
result in serious injury and vehicle damage.
Before returning to the paved road, re-in-
flate your tires to the recommended pres-
sure. Also, be aware that tires with lower
pressure will hydroplane easier on paved
surfaces. Check your owner’s manual for
recommended on-road tire pressure.
Keep in mind that lowering tire pressure
also lowers the clearance of the vehicle
over the ground. Lower pressure spreads
the weight of your vehicle over a larger
patch of tire that is in contact with the
ground. Because the tire spreads, your
sidewalls will be more susceptible to
damage.
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