Evening star., 1922-12-24
FOUR WHEEL BRAKES HELP
TO SOLVE SKID PROBLEMS
Treads and Chains Properly Handled
Greatly Minimize Danger in Traffic
on Wet Streets.

Why an automobile skids is Of in
.erest to a motorist, but what to do
TO prevent skidding and what to do
when the car is skidding are equally
important topics. says B. J. Lemon
of the United States Tire Company.
The main cause of skidding of rear
wheels of motor cars is due to the
brakes operating through the rear
wheels. Skidding. of course. nor
mally occurs only when the roads
are slippery.
An automobile wheel rotates and
progresses over the highway in but
one direction or plane. This direc-
tion for the rear wheels is determined
by the front wheels under control
Of the driver. While the rear wheels
grip the ground and rotate they con-
troll the direction of the car. How
ever, as soon as the rear wheels are
locked by the brakes they begin to
tically as easily as forward they
lose the power to direct the car.
1t takes comparatively little brake
friction to lock and slide rear wheels
on slippery roads because there fs
little friction between the tire and
driving wheels begin to slip the car
is kept in motion by the force Of
inertia acting at the cars senter OF
gravity or mass. This forward mo-
sion is opposed by the resistance OF
all four wheels on the ground. a re-
sistance that is greater in the rotat-
ing front wheels than in the sliding
rear wheels. Unless the combined
ground resistance of all wheels tend
ing to stop the car acts on the same
point as the force Of inertia tending
to carry the car forward. there re-
which causes the car to skid or spin
around.
"Force Couple'' and Skid.
After the wheels once start to slip.
q very small "force couple" will pro-
duce skidding, and the skid distance
Ia dependent upon the magnitude of
the force COUPLE" which. in turn. de-
pends on car speed and weight. Turn
ing the front wheels in the direction
duce skidding, because it reduces the
Magnitude of the force couple" Also
periodically relea sing and reapplying
the brake SO the rear wheels can get
zgrip offsets forward slip and conse-
0uent side skid.
Vent skidding In motor vehicles. The
use of non-skid or rough-tread tires
and Of anti-skid chains. Non-skid
tires are designed to give forward
traction and to prevent side slip. AS
6ng as there Is traction the rear
theels will turn and as long as the
Sear wheels turn there will be no
serious side slip. unless the front
Wheels are blocked.
SNon-skid tires furnish reliability
and safety In driving-re1iability. in
permitting the vehicle to operate sue
cessfuily over almost any kind of
road and during all seasons Of the
year. and safety by permitting the
vehicle to hold the road at all speeds
and allowing the brakes to be most
Nom skid treads on tires were first
used on rear wheels and are now
considered absolutely essential for
such uses. Later non-skid tires were
placed on front wheels. because the
treads prevented front-wheel skid
ding, as we'll an permitting the rota-
ton or exchange of the front and
rear tires.
Check to Rear Wheel Skid.
a well designed. non-skid tread
should give on rear wheels sufficient
forward traction to permit the car
20 operate without chains under most
road conditions and at the same time
insure against side slip. 1t must per-
NIT quick and smooth response to
clutch accelerator and brakes. 1t
must not greatly impair ease of steer
ing when used on front wheels. 1t
must not set up vibration in the car
nor produce disagreeable humming
noises.
Non-skid chains accomplish the
same purpose as the non-skid tire
tread-that is. give additional trac-
ton and reduce side slip. Non-skid
chains should supplement non-skid
tires only when road conditions alb
Solutely require them
Because they make available in
road friction the total weight Of the
car instead Of only half the car
weight, four-wheel brakes are coming