Page 26 - 2017-v.2-Part 4(EN)

4.6.4 Back-pedal brake linearity test

This test shall be conducted on a fully assembled bicycle. The output force for a back-pedal brake shall be
measured tangentially to the circumference of the rear tyre, when the wheel is rotated in the direction
of forward movement, while a force of between 90 N and 300 N is being applied to the pedal at right
angles to the crank and in the direction of braking.

The braking force reading shall be taken during a steady pull and after one revolution of the wheel. A
minimum of five results, each at a different pedal force level, shall be taken. Each result shall be the
average of three individual readings at the same load level.

The results shall be plotted on a graph, showing the line of best fit and the ±20 % limit lines obtained by
the method of least squares outlined in Annex A.

4.6.5 Machine test method

4.6.5.1 General

The test machine enables the braking distances for both brakes or the rear brake alone to be calculated
from measurements of the individual braking forces of the front and rear brakes on a drum or belt.

4.6.5.2 Symbols

F Op Operating force (i.e. force applied on brake lever or pedal)

F Op intend Intended operating force (e.g. 40 N, 60 N, 80 N etc.)
F Op rec Recorded operating force (e.g. 38 N, 61 N, 79 N etc.)

F Br Braking force

F Br rec Recorded braking force

F Br corr Corrected braking force (Corrected for difference between F Op intend and F Op rec)

F Br average Arithmetic mean of the three F Br corr at one level of F Op intend

F Br max Maximum F Br average

F Br Dry braking force
D

F W Br Wet braking force

4.6.5.3 Linearity

When tested by the methods described in 4.6.5.7 item c) 1) and 2), the braking force F Br average shall be
linearly proportional (mountain and racing bicycle are within ±10 %, city and young adult bicycles are within ±
20 %) to the progressively increasing intended operating forces F Op intend. The requirement applies to
braking forces F Br average equal to and greater than 80 N (see Annex A).

4.6.5.4 Test machine

The test machine shall incorporate a system that drives the wheel during the test by tyre contact and a
means of measuring the braking force, and typical examples of two types of machine are illustrated in
Figures 14 and 15.

Figure 14 shows a machine in which a roller drives the individual wheels, and Figure 15 shows a machine
in which a driven belt contacts both wheels. Other types of machine are permitted, provided they meet
the specific requirements listed below and those specified in 4.6.5.5 and 4.6.5.6.

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