Division 2

In order to be recognised as equivalent to air suspension, a suspension shall comply with the following requirements:

1. 2.1.

   During free transient low-frequency vertical oscillation of the sprung mass above a driving axle or group of axles, the measured frequency and damping with the suspension carrying its maximum load shall fall within the limits defined in points 2.3 to 2.6

2. 2.2.

   Each axle shall be fitted with hydraulic dampers. On groups of axles, the dampers shall be positioned to minimise the oscillation of the groups of axles.

3. 2.3.

   The mean damping ratio Dm shall be more than 20 % of critical damping for the suspension in its normal condition with hydraulic dampers in place and operating.

4. 2.4.

   The damping ratio Dr of the suspension with all hydraulic dampers removed or incapacitated shall be not more than 50 % of Dm.

5. 2.5.

   The frequency of the sprung mass above the driving axle or group of axles in a free transient vertical oscillation shall not be higher than 2,0 Hz.

6. 2.6.

   The test procedures for measuring the frequency and damping shall be laid down in point 3.