Page 12 - 20190101 part 6 (EN)

TBIS 4210-6:2019

4.2 Frame and front fork assembly — Impact test (falling frame)

4.2.1 General

Manufacturers of complete bicycles shall conduct the test with the frame fitted with the appropriate
front fork.

For manufacturers of frames, where the fork intended for the frame is not available, the test can be
conducted with the frame fitted with a fork which meets the requirements of the fork impact test as
described in TBIS 4210-2:2017, 4.9.5.

Where a frame is convertible for male and female riders by the removal of a bar, test it with the bar
removed.

Where a suspension fork is fitted, it shall be at its unloaded length prior to the impact. If the spring/damper
unit can be locked, it shall be locked in its unloaded length position. If the spring/damper cannot be
locked, use one of the two following alternative procedures:

— secure the fork at its extended length by an external locking method, or

— replace the fork by a rigid fork which is known to meet the requirements of the impact test described
in TBIS 4210-2:2017, 4.9.5 and of a length which is consistent with an 80 kg (in case of young
adult bicycles, apply 40 kg) rider seated in a normal riding position on the bicycle when it is
equipped with the suspension fork.

Where a rear suspension system is incorporated in the frame, secure the spring/damper unit in a
position equivalent to that which would occur with an 80 kg (in case of young adult bicycles, apply
40 kg) rider seated on the bicycle; if the type of suspension system does not permit it to be locked, then
replace the spring/damper unit by a solid link of the appropriate size and with end fittings similar to
those of the spring/damper unit.

4.2.2 Test method

4.2.2.1 Stage 1

Conduct the test on the assembly used for the test in TBIS 4210-2:2017, 4.8.2 or, in the case of a
frame manufacturer who does not make forks, with the same frame with a suitable fork fitted (see
4.2.1).

As shown in Figure 2, mount the frame-fork assembly at its rear axle attachment points so that it is free
to rotate about the rear axle in a vertical plane. Support the front fork on a flat steel anvil so that the
frame is in its normal position of use. Securely fix mass M 1 to the seat-post as shown in Figure 2 with
the centre of gravity at distance D (= 75 mm) along the seat-post axis from the insertion point, and fix
masses of M 2 and M 3 (Ta ble 2) to the top of the steering head and the bottom bracket, respectively, as
shown in Figure 2.

Measure the wheelbase with the three masses in place. Rotate the assembly about the rear axle until the
distance between the low-mass roller and the anvil is h 2, then allow the assembly to fall freely to impact
on the anvil.

Repeat the test and then measure the wheelbase again with the three masses in place and the roller
resting on the anvil.

If the frame meets the requirement as specified in TBIS 4210-2:2017, 4.8.3, and conduct stage 2 of the
test with the assembly in the same mountings.

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