Gradeability is an important specification when selecting an electric stacker, especially when the machine needs to travel across ramps, loading areas, warehouse transitions, or slightly inclined floors.

However, a common misunderstanding is that a stacker with a maximum gradeability of 6% can safely operate on any 6% slope under all conditions.

In reality, gradeability depends on load weight, battery condition, floor surface, ramp length, wheel traction, machine configuration and operating direction.

Published specifications show significant differences between electric stacker models. For example, Linde's MM10 pedestrian pallet stacker lists a maximum gradeability of 5% with load and 15% without load, while a LiuGong 1.6-ton pedestrian stacker lists 6% with full load and 12% unloaded. Toyota's walkie straddle stacker models list up to 6% maximum gradeability at full load.

Therefore, gradeability should always be evaluated together with the actual operating conditions.

What Is Electric Stacker Gradeability?

Electric stacker gradeability refers to the maximum slope that the machine can travel under specified operating conditions.

It is normally expressed as a percentage (%), rather than degrees.

For example:

A 6% grade means the elevation changes approximately 6 meters for every 100 meters of horizontal distance.

So a 6-meter rise over a 100-meter horizontal distance corresponds approximately to a 6% grade.

This is an important distinction because 6% does not mean a 6-degree slope.

What Does a 5% or 6% Grade Look Like?

A warehouse ramp can look relatively flat while still having a measurable gradient.

For example:

5% Grade

For every 10 meters of horizontal travel:

10 m × 5% = 0.5 m

The elevation changes approximately 0.5 meters.

6% Grade

For every 10 meters:

10 m × 6% = 0.6 m

The elevation changes approximately 0.6 meters.

Therefore, even a relatively modest-looking ramp can create a significant change in elevation over a long travel distance.

What Gradeability Do Electric Stackers Typically Have?

There is no single standard gradeability value for all electric stackers.

Published specifications provide a useful reference.

The Linde MM10 series specifies 5% maximum gradeability when loaded and 15% unloaded. LiuGong's 1.6-ton pedestrian stacker specifies 6% loaded and 12% unloaded. Toyota's walkie straddle stacker specifications list 6% maximum gradeability at full load across the cited models.

These figures demonstrate an important point:

An electric stacker's climbing ability can be significantly different when loaded and unloaded.

Why Does Load Weight Affect Gradeability?

When an electric stacker carries a pallet, the total mass of the machine and load increases substantially.

For example, consider a 1.5-ton electric stacker.

If the machine weighs 600 kg and carries a 1,500 kg load:

Total moving mass = 600 + 1,500 = 2,100 kg

The drive system must move approximately 2.1 tons of combined machine and load mass.

When the same machine travels without a load, it may only need to move approximately 600 kg.

This is one reason manufacturers usually provide separate loaded and unloaded gradeability figures.

For example, the LiuGong CLG2S016-WF3 has a rated capacity of 1,600 kg, while its maximum gradeability is specified as 6% fully loaded and 12% unloaded.

Which Floor Conditions Can an Electric Stacker Handle?

Gradeability is most relevant when the floor is not completely level.

1. Flat Concrete Warehouse Floors

This is the easiest operating environment.

A conventional warehouse with:

• Flat concrete

• Smooth surface

• No significant ramps

• Good traction

generally does not place major demands on gradeability.

In this situation, buyers may place greater emphasis on:

• Lift height

• Rated capacity

• Turning radius

• Aisle width

• Battery capacity

• Travel speed

Gradeability is still important, but it is usually not the primary selection factor.

2. Warehouse Ramps

Ramps are one of the most important applications for gradeability.

For example, a warehouse may have a ramp connecting two floors.

If the ramp is 5%, the machine needs to overcome that slope while carrying the load.

If the selected stacker's rated gradeability with load is 6%, the published specification indicates that the machine is designed to negotiate a 6% grade under the manufacturer's specified test conditions.

However, this does not mean that operating continuously at 6% is recommended.

A practical design should consider some margin between the actual ramp gradient and the machine's maximum rated gradeability.

3. Loading Dock Ramps

Loading docks can create a combination of:

• Inclination

• Surface transitions

• Uneven sections

• Metal dock plates

• Changes in traction

This makes gradeability only one part of the evaluation.

For example, a stacker might have:

Maximum gradeability with load: 6%

But the loading dock could have:

Actual ramp: 5%

On paper, the machine meets the gradeability requirement.

However, if the dock surface is wet or slippery, available traction may decrease.

Therefore:

Gradeability is a performance specification, not a guarantee of safe operation on every surface.

4. Slightly Uneven Warehouse Floors

Gradeability can also become relevant when a warehouse floor has minor inclines.

Examples include:

• Old industrial buildings

• Warehouse entrances

• Sloped drainage areas

• Floor transitions

• Connecting corridors

In these applications, buyers should consider gradeability together with ground clearance and wheel configuration.

This is especially important because a machine may be able to climb a slope but still have difficulty crossing a sharp transition between two floor surfaces.

5. Outdoor Yard or Rough Ground

This requires much more caution.

A conventional indoor electric stacker should not automatically be considered suitable for:

• Gravel

• Dirt

• Mud

• Broken concrete

• Uneven outdoor yards

• Steep unpaved ramps

For example, one commercially available 3,300-lb walkie electric stacker lists 3% loaded and 7% unloaded gradeability, but its manufacturer specifically limits the machine to flat, level indoor surfaces and warns against use on ramps, uneven yards, gravel and rough outdoor surfaces.

This illustrates an important SEO and buyer-education point:

Maximum gradeability alone does not define the complete operating environment.

Gradeability vs. Ground Clearance

These two specifications are often confused.

They solve different problems.

For example, Linde's current MM10/MM10i/ML10 data lists ground clearance of 28–35 mm, depending on model, while maximum gradeability is 5% loaded and 15% unloaded.

A machine can therefore have sufficient gradeability but insufficient ground clearance for a particular floor transition.

How Does Floor Surface Affect Gradeability?

The published gradeability figure is generally measured under specified conditions.

Actual performance can change with surface conditions.

Smooth, dry concrete

Provides relatively good traction and predictable travel.

Wet concrete

May reduce tire or wheel traction.

Dusty floor

Dust, powder or debris can affect wheel grip.

Oil-contaminated floor

Can significantly reduce traction and increase stopping distance.

Gravel

Loose material can reduce traction and increase rolling resistance.

Uneven concrete

May create additional mechanical resistance and vibration.

This is why the same electric pallet stacker can behave differently on two surfaces with identical slopes.

Case Example: 1.5-Ton Electric Stacker on a 5% Ramp

Suppose a distributor is selecting an electric stacker for a warehouse with:

• Rated load: 1,500 kg

• Ramp gradient: 5%

• Ramp length: 20 m

• Surface: dry concrete

• Load: approximately 1,300–1,500 kg

The first step is to compare the loaded gradeability with the actual 5% ramp.

If the selected model has:

Maximum loaded gradeability = 6%

then the published specification is above the 5% requirement.

However, the buyer should also verify:

1. Whether the 6% figure applies at the required load

2. Wheel and floor conditions

3. Braking performance

4. Direction of travel

5. Ramp transition geometry

6. Whether the manufacturer permits ramp operation

7. Whether the load must be carried uphill or downhill

This is more reliable than simply seeing "6% gradeability" on a product page.

Why Loaded and Unloaded Gradeability Should Be Listed Separately

Consider two published examples:

Linde MM10:

• Loaded: 5%

• Unloaded: 15%

LiuGong CLG2S016-WF3:

• Loaded: 6%

• Unloaded: 12%

The difference is substantial.

For buyers, this means the number that matters most is normally the gradeability under the actual working load, not the unloaded figure.

If a customer regularly moves 1,500 kg pallets, the unloaded gradeability should not be used to determine whether the machine can handle a ramp.

What Other Electric Stacker Specifications Should You Check?

When the machine will operate on ramps or inclined floors, check the following specifications together:

Linde's current L10–L16 B product information specifically highlights gradeability for work on gradients and also notes an initial-lift function that provides additional ground clearance for uneven floors or ramps.

How to Calculate Warehouse Ramp Gradient

If the ramp dimensions are known, the approximate gradient can be calculated as:

Grade (%) = Vertical Rise ÷ Horizontal Run × 100

Example

A ramp rises:

0.8 m

over a horizontal distance of:

16 m

Then:

0.8 ÷ 16 × 100 = 5%

Therefore, the ramp has an approximate 5% grade.

This simple calculation is useful when customers are selecting an electric stacker for a warehouse or loading area.

Practical Electric Stacker Gradeability Selection Guide

A useful preliminary approach is:

These are selection guidelines rather than universal limits. The manufacturer's operating manual and application-specific specifications should always take priority.

Final Takeaway

Electric stacker gradeability tells you how steep a slope the machine is designed to negotiate under specified conditions, but it does not by itself determine whether the machine is suitable for every floor condition.

For warehouse applications, published electric stacker specifications commonly show loaded gradeability in the range of approximately 5–6% for several pedestrian models, while unloaded values can be considerably higher. For example, Linde lists 5% loaded / 15% unloaded for the MM10, and LiuGong lists 6% loaded / 12% unloaded for its 1.6-ton pedestrian stacker.

When selecting an electric stacker for ramps, buyers should evaluate:

Actual slope + actual load + floor surface + traction + ground clearance + braking + manufacturer's operating limits.

The most important number is therefore not simply the highest gradeability listed in a catalog. It is the loaded gradeability under the customer's actual working conditions.

This makes gradeability an important specification for choosing the right electric pallet stacker, especially when the machine will operate between warehouse floors, loading docks or other areas where completely level flooring cannot be guaranteed.