What Does Gradeability Mean on a Heavy Duty Forklift?

A buyer checking a forklift specification sheet may see:

Gradeability: 20% / 22%

It looks like a simple number, but it is easy to misunderstand.

For a heavy duty forklift, gradeability matters whenever the truck needs to move between different floor levels, use a loading ramp or travel through an inclined yard.

Gradeability is normally expressed as a percentage.

A 20% gradient means the surface rises 20 units vertically over 100 units of horizontal distance.

It does not mean a 20-degree slope.

A 20% gradient is roughly equivalent to an angle of 11 degrees.

This distinction is worth checking when customers provide site information, because "20%" and "20 degrees" describe very different ramps.

Specification sheets may show two gradeability figures.

For example:

Loaded: 20%
Unloaded: 22%

The forklift can normally negotiate a steeper gradient when it is not carrying its rated load.

This is why we ask:

Will the truck climb the ramp while loaded or empty?

For a 25-ton forklift, climbing a ramp empty and climbing the same ramp with a 25-ton load are completely different operating conditions.

Manufacturers such as Konecranes also publish loaded and unloaded gradeability separately in their technical data.

Some technical specifications distinguish between continuous and short-duration gradeability.

A truck may be capable of negotiating a steeper slope for a short period than it can handle continuously throughout a shift.

That is why a buyer should not simply compare:

Brand A: 20%
Brand B: 25%

without checking how those figures were defined.

The duty cycle still matters.

A dry concrete ramp provides very different traction from:

• Wet concrete
• Loose gravel
• Dusty yard surfaces
• Mud
• Steel plates

The gradient may be the same, but the available traction is not.

For this reason, when a customer tells us the forklift has to work on a slope, we also ask what the ramp surface is made of.

Descriptions such as:

"There is a small slope."

are difficult to use for forklift selection.

If the ramp is important to daily operation, provide:

Ramp length
Vertical rise
Surface condition
Maximum load carried on the ramp

A photo or short video is also useful.

A forklift being capable of climbing a slope does not mean it should travel quickly on that slope.

OSHA requires grades to be ascended or descended slowly. For grades greater than 10%, loaded trucks should travel with the load positioned upgrade.

The truck's braking performance, load position and operating surface still need to be considered.

It deserves particular attention when the forklift will work in:

• Multi-level factories
• Port yards
• Construction-material plants
• Loading docks
• Industrial sites with ramps
• Outdoor yards with changing elevation

For a completely flat factory, gradeability may not be a deciding specification.

For a site where every load crosses a ramp, it can be much more important.

If a customer tells us a heavy duty forklift must regularly climb a ramp, the three pieces of information we want first are:

Gradient + load weight + surface condition

Once these are clear, we can evaluate the powertrain and truck configuration much more realistically.

References

• OSHA - Powered Industrial Trucks, Traveling on Grades.
• OSHA - Workplace Conditions and Sloped Surfaces.
• Konecranes - Technical Data: Loaded and Unloaded Gradeability.