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BRAKING FACTS.
R.A.C. Tests.
(By Robert Shave, A.M.I.A.E., technical
adviser of the Royal Automobile
Club of W.A.)
THE ability to stop a car quickly in an
emergency is of the very greatest im
portance. It is quite the usual thing
for a motorist to state that he can stop
his ' car in a couple of yards, or in its
own length. The first is an impossibility,
and the second extremely unlikely.
Brakes of 100 per cent efficiency will
stop a car hi 13jffc, but such an efficiency
is not found in an ordinary car.
Mot long ago the Royal Automobile
Club purchased a Tapley brake meter for
measuring the efficiency of brakes, and
a system for the free testing of members'
car brakes was inaugurated. Many mem
bers availed themselves of this with the
following results:—
5 per cent were found to be hi a
dangerous condition.
48 per cent were poor.
14 per cent were hi fair condition.
15 per cent were hi good condition.
18 per cent we,re excellent.
In most cases it was found that brak
ing could be vastly unproved by a simple
adjustment, sometimes by merely lubri
cating the operating gear. It is astonish
ing how the efficiency of a mechanical
type brake is sometimes unproved by
lubricating the cross shafts and clevis
joints. In classifying the cars tested the
following percentages of efficiency were
used for cars with four-wheel brakes: —
Below 30 per cent efficiency: Danger
ous.
Over 30 and below SO per cent: Poor.
Over SO and below 60 per cent: Fair.
Over 60 and below 70 per cent: Good.
Over 70 per cent: Excellent.
Some of the cars tested showed brak
ing efficiencies of well over 90 per cent.
It was rather alarming to note that 67
per cent were below the 'good' standard.
Brakes should receive attention just as
much as, for Instance, engine lubrica
tion. Insufficient oil will shorten the life
of an engine, but inefficient brakes may
shorten the life of drivers, passengers,
or some unfortunate pedestrian.
The actual effect of inefficient brakes
will be better realised when the stopping
distance of a car is considered. At 25
miles per hour a car with brakes of 30
per cent efficiency will take 69ft. to
make an emergency stop after the brakes
are applied. Careful tests have shown
that a driver faced with an unexpected
emergency *-top takes over one second
to realise the fact and to apply the
brake, and in that period of tune a car
travelling 25 m.p.h. covers 37ft.
Even from so low a speed as 25 miles
per hour, therefore, 106ft. is covered
after an emergency arises before the car.
stops, if the brakes have only 30 per cent
efficiency. With good brakes of 60 per
cent efficiency the total stopping distance
is reduced-to 72ft.
The wise motorist will never take a
risk with brakes. How much better it
is to ensure that they are working
efficiently than to be subject to bitter
regrets after an accident has occurred.
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