Page 32 - 2018-v.3-Part 2(EN)
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4.15 Chain-wheel and belt-drive protective device

4.15.1 Requirements

City and trekking and young adult bicycles shall be equipped with

a) a chain wheel disc or drive pulley disc which conforms to 4.15.2,

b) a chain and drive belt protective device which conforms to 4.15.3, or

c) where fitted with positive foot-retention devices on the pedals, a combined front gear-change guide
which conforms to 4.15.4 shall be used.

Mountain and racing bicycles can be equipped with one of the above-mentioned.

4.15.2 Chain-wheel disc and drive pulley disc diameter

A chain-wheel disc shall exceed the diameter of the outer chain wheel, when measured across the tips of
the teeth, by not less than 10 mm (see Figure 6).

A drive pulley disc shall exceed the diameter of the front pulley, when measured across the tips of the
teeth, by not less than 10 mm (see Figure 7). Where the design is such that the crank and chain wheel or
the crank and front pulley are too close together to accommodate a full disc, a partial disc can be fitted
which closely abuts the crank.

Dimensions in millimetres























Key
1 chain-wheel disc (D 2 ≥ D 1 + 10)


Figure 6 — Chain-wheel disc
















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