Troubleshooting guide

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FIGURE 3 - EFFECT OF WEIGHT AND SPEED ON BRAKING FORCE REQUIRED
(Note: For illustration the Figure above shows horses; however in this case we are illustrating the effect of forces, not horsepower amounts, as we were in Figure 2.)
Braking Force
The Effect of Weight and Speed
Other factors that affect braking performance
include the weight and speed of the vehicle. If the
weight of the vehicle is doubled, the energy of motion
to be changed into heat energy is also doubled. Poor
braking performance results when the brake cannot
dissipate and absorb the increased heat caused when
a vehicle’s weight exceeds the design spec’s. Brake
systems are designed to control a vehicle loaded up to
its gross vehicle weight (GVW). That’s why it’s critical to
never exceed the GVW for a vehicle.
FIGURE 4 - EFFECT OF SPEED ON STOPPING DISTANCES
The effect of higher speeds on braking is even more
signifi cant. Compare stops from speeds of 20 miles per
hour and 40 miles per hour. Engineering calculations
show that four times as much energy of motion must to
be changed to heat energy during a stop from 40 miles
per hour as during a stop from 20 miles per hour. If the
speed is doubled, therefore, four times as much stopping
power must be developed, and the brakes must absorb
– or dissipate – four times as much heat. If the speed is
three times higher, the stopping power needed is nine
times higher.
It follows that if both the weight and speed of a vehicle
are doubled, the stopping power must be increased eight
times and the brakes must absorb or dissipate eight
times as much heat.
Another way of illustrating the effect of speed on stopping
ability is to compare the stopping distance if the speed is
increased without increasing the weight.
In Figure 4, the vehicle shown stops from 20 miles per
hour within 30 feet. At 40 miles per hour, it typically
requires 120 feet to stop. At 60 miles per hour, the typical
stopping distance is 270 feet.