Forklifts are unstable by design. They have no springs and even four wheel counterweighted forklifts only have
three point suspension.

The two rear wheels are attached in the centre to the main body of the machine allowing the rear to hinge
sideways affecting the lateral (sideways) stability of the machine. All forklifts have a high centre of gravity
and a narrow wheel base which adds to their lateral
instability.

Forklifts have three point suspension formed from the front drive axle (a & b) and the steering axle point at the rear
of the base (c). Be aware of the factors listed below which can affect lateral instability:

• turning at speed
• driving over uneven surfaces
• an unevenly distributed load
• driving with a flat or under inflated tyre
• driving too fast
• travelling with the load raised
• braking too hard when turning
• side shift not centred
• lifting a load on one fork armdriving sideways across a slope
• dragging (snigging) a load sideways with a jib
• attachment.

The front wheels of forklifts act as a fulcrum with the forks on one side and the machine body on the other. If the weight at the fork ends is heavier than the counterweight it will cause the forklift will tip up (longitudinal instability).

Be aware of the factors listed below which can affect the forklift to tip (longitudinal instability):

• overloading
• severe braking
• incorrect use of the mast tilt (especially with the load carried at a higher level)
• load not positioned against the heel of the fork arms
• shifting the load centre forward
• dragging (snigging) a load in from the front with the jib attachment fitted
• lifting a load with a jib with the mast tilted forward
• picking up an over-width load
• fitting slipper forks
• driving with reach extended.

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