Page 35 - TBIS_79010-2019_(EN)_1nd

TBIS 79010:2019

4.3.4 Frame and front fork assembly – Fatigue test with horizontal forces
4.3.4.1 General
It is not necessary for a genuine fork to be fitted, provided that any substitute fork is

of the same length as the intended fork and it is correctly installed in the
steering-head bearings.

Ensure that the axes of the front and rear axles are horizontally in line, as shown in
Figure 11. For suspension-frames in which the chain-stays do not have pivots but rely
on flexing, ensure that any dampers are set to provide the minimum resistance in
order to ensure adequate testing of the frame.

Where a suspension frame has adjustable brackets or linkages to vary the resistance
of the bicycle against the ground-contact forces or to vary the attitude of the bicycle,

arrange the positions of these adjustable components to ensure maximum forces in
the frame.
For a suspension frame and front fork, lock it at a length equivalent to that with

maximum permissible total weight by adjusting the spring/damper or by external
means.

4.3.4.2 Requirement
When tested by the method described in 4.3.4.3, there shall be no visible cracks or
fractures in the frame and there shall be no separation of any parts of any

suspension system.
For composite frames, the running displacement (peak-to-peak value) at the point

where the test forces are applied shall not increase by more than 20 % of the initial
values (see 4.3.1.6).
4.3.4.3 Test method

Mount the frame in its normal attitude and secured at the rear drop-outs so that it is
not restrained in a rotary sense (i.e. preferably by the rear axle) as shown in Figure

11. Ensure that the axes of the front and rear axles are horizontally in line.
Apply cycles of dynamic, horizontal forces of F 3 in a forward direction and F 4 in a
rearward direction to the front fork drop-outs for C 1 cycles as shown in Table 7 and

Figure 11, with the front fork constrained in vertical direction but free to move in a
fore/aft direction under the applied forces. The maximum test frequency shall be
maintained as specified in 4.1.1.5.

Table 7 — Forces and cycles on front fork drop-outs
Forward force F 3，N 1200
Rearward force F 4，N 600
Test cycles, C 1 50 000

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