Page 71 - Driving Commercial Vehicles Manual

chapter 3 — basic driving skills

Vehicle safety
fast fact
Keep your vehicle in top condition at all times. Your tires, wheels and lights
Driving on a flat tire may need to be in good working order.
cause more damage —
including a tire fire — and
could mean you will have Tires and wheels
to replace the tire rather Don’t drive a vehicle with its tires, wheels or rims in poor condition — it’s
than have it repaired. Tires
that have caught fire could extremely dangerous and illegal. Inspect your tires, wheels and rims before
spread to your truck or trailer. every trip.

Tire pressure
The rolling of your wheels as you drive cause your tires to flex, creating friction
and generating heat. Usually, tires release this heat to the air around them.

fast fact If your tires are the correct size and are correctly inflated, and if your vehicle
is not overloaded, the heat generated by your tires shouldn’t cause any
problems.
If you reduce a tire’s air
pressure when it’s warm, If your tires are not properly inflated at the start of a trip, you risk tire damage
you may upset the cooling or even a blowout because of excessive heat buildup. A major cause of failure
balance and cause the tire to in recapped (retread) tires is underinflation.
generate more heat.
If your tires are underinflated, your load is too heavy or you’re driving too fast,
your tires will flex more. More flexing means more heat. Too much flexing
can cause your tires to overheat and the tire air pressure to increase. If this
pressure rises too high, your tires could burst.
fast fact Manufacturers put a load rating on their tires. Check what these ratings are for
your tires. Keep the weight of your vehicle and load below the rating for any
When the amount of contact individual tire or any group of tires on a single axle.
between the tire and the Check and adjust tire pressure when tires are cool. Use a tire pressure gauge.
road surface is reduced, If a tire has the correct pressure when it’s cool, it will generate a normal
steering control is also
reduced. amount of heat during use. This will reduce the amount of wall flexing, which
also keeps heat buildup under control.

Tire wear
Improperly inflated tires also cause your tires to wear out more quickly and
driving tip may reduce the amount of steering control you have.

Overinflating a tire causes excess wear in the centre part of its tread. An
Driving at 110 km/h can
reduce tread life by 20 per overinflated tire has less tread surface in contact with the road surface. Less
cent compared to driving contact between your tire and the road means less traction.
at 90 km/h.
Underinflating a tire causes excess wear on the outer edges of its tread. In wet
The faster you drive, the more conditions, an underinflated tire will not squeeze the water out from between
fuel you will use. the tire and the road as well as a properly inflated tire and has a greater
chance of riding on a film of water (hydroplaning).

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