Why Do Heavy Duty Forklifts Often Use Dual Front Tires?

Look at a large counterbalance forklift from the front and you may notice something different from a small warehouse truck.

Instead of one tire on each side of the front axle, many high-capacity forklifts use:

two tires on the left + two tires on the right.

That gives the truck four front tires and two rear tires.

On a specification sheet, this may appear as:

4X / 2

where the front wheels are also the driven wheels.

Why does a heavy duty forklift need this arrangement?

The main reason is not appearance or simply making the truck wider. It is closely related to how a counterbalance forklift carries weight.

A counterbalance forklift carries the load in front of the front axle.

When the truck is empty, its own weight is shared between the front and rear axles.

Once a heavy load is placed on the forks, the distribution changes considerably.

Much more of the combined truck-and-cargo weight is supported by the front axle.

We discussed this separately in our article "Why Does Axle Load Matter on a Heavy Duty Forklift?"

A published Hyster H300XD example illustrates the effect clearly: its loaded front axle carries far more weight than its rear axle.

For a high-capacity forklift, the tires on that front axle therefore have a demanding job.

Every tire has an allowable load range.

The correct capacity depends on factors such as:

• Tire size
• Tire construction
• Inflation pressure for pneumatic tires
• Vehicle speed
• Application
• Duty cycle

When four tires are installed across the front axle instead of two, the axle load can be distributed across more tires.

This allows the tire arrangement to be matched to the very high front axle loads found on larger forklifts.

It also explains why the front and rear tire arrangements do not necessarily need to be identical.

When the forklift is carrying its rated load, the rear axle may carry only a relatively small portion of the total weight compared with the front.

Some forklift specification sheets show the number of wheels in a format such as:

4X / 2

The first number refers to the front wheels.

The second refers to the rear wheels.

The X indicates the driven wheels.

So:

4X / 2

normally means:

• Four front wheels
• Front axle is driven
• Two rear wheels

Hyster, for example, publishes a 4X/2 wheel arrangement on its H155–170FTS series.

This is a useful detail when comparing high-capacity forklift specifications because simply listing the tire size does not tell you how many tires are fitted.

Not by itself.

This is an important distinction.

Changing from two front tires to four does not automatically increase a forklift's rated capacity.

Forklift capacity still depends on the complete design, including:

• Chassis
• Mast
• Forks
• Drive axle
• Counterweight
• Wheelbase
• Braking system
• Load center
• Tires

The tire arrangement is one part of that system.

If a forklift was engineered and approved as a 16-ton truck, adding another pair of tires does not turn it into a 20-ton forklift.

It is also too simple to calculate:

Front axle load ÷ 4 = required tire capacity

and stop there.

Industrial tire manufacturers publish load tables according to the actual application.

For pneumatic industrial tires, the permitted load can change with inflation pressure, traveling speed and operating conditions.

Michelin, for example, publishes separate load data for counterbalance lift-truck load wheels and specifies that inflation pressure must match the load per tire, travel speed and work being performed.

So tire selection should follow the applicable tire manufacturer's technical data rather than a basic arithmetic calculation alone.

Dual front tires do not make tire size irrelevant.

Two forklifts may both use four front tires but use very different:

• Tire diameters
• Tire widths
• Ply ratings or load indexes
• Rim sizes
• Inflation pressures

This is why buyers should read:

tire quantity + tire size + tire type

together.

For example, a specification that only says:

Pneumatic tires

does not give enough information to compare the front-end configuration of two heavy duty forklifts.

In theory, a larger tire can carry a higher load if it is designed and rated for that application.

But forklift design involves more than finding the largest possible tire.

Larger tires can affect:

• Overall truck width
• Mast and chassis packaging
• Steering and clearance
• Axle design
• Rim availability
• Replacement cost
• Final machine dimensions

Using dual tires allows manufacturers to reach the required axle-load capability while working within the overall vehicle design.

The exact choice depends on forklift capacity and engineering layout.

That is why some heavy forklifts use dual front tires while other designs use very large single tires.

When two pneumatic tires are mounted side by side, they cannot simply be placed at any distance.

Industrial tire manufacturers specify a minimum dual spacing for applicable tires.

For example, Michelin publishes minimum dual-spacing data for its industrial X-STACKER tire range.

Correct spacing helps ensure that the dual assembly works within the tire manufacturer's intended installation conditions.

This is one of the reasons a dual-tire conversion should not be treated as a casual modification after delivery.

The rims, hubs, axle and available clearance all need to suit the configuration.

It can spread the front axle load across more tire contact areas, but buyers should be careful with the conclusion:

"Four tires means the floor load is no longer a problem."

That is not necessarily true.

A heavy duty forklift may still place a very large load on the floor.

For factories, platforms, ramps or dock areas with structural limits, the important figures can include:

• Loaded front axle weight
• Tire arrangement
• Individual wheel or tire loads
• Floor capacity
• Travel route

Adding tires does not make the total machine-and-cargo weight disappear.

For structural floor calculations, the site engineer should evaluate the actual forklift configuration.

For pneumatic tires, matching inflation pressure matters.

If two tires working as a pair are not maintained correctly, the load may not be shared as intended.

Industrial tire manufacturers therefore specify operating pressures according to the load and application.

Continental also emphasizes using the manufacturer's load and inflation information to determine tire capacity and correct pressure.

For a heavy duty truck, tire-pressure inspection should therefore cover all tires in the dual assembly, not only the easily visible outer tire.

Dual front tires introduce one practical maintenance point:

the inner tire is less visible.

During inspection, operators and maintenance personnel should pay attention to both tires in each pair.

Things worth checking include:

• Inflation pressure on pneumatic tires
• Cuts or sidewall damage
• Abnormal wear
• Objects trapped between paired tires
• Rim condition
• Loose or damaged wheel hardware

Checking only the outer tire gives an incomplete picture of the front wheel assembly.

On a conventional counterbalance forklift, the rear axle performs a different job.

It carries part of the truck weight, but when a heavy load is placed on the forks, much of the working weight transfers toward the front axle.

The rear axle is also normally the steering axle.

As a result, the front and rear wheel systems are designed around different loads and functions.

This is why a high-capacity forklift may have:

four front tires + two rear tires

without needing dual tires at both ends.

When comparing heavy duty forklift quotations, do not look only at the tire brand or whether the truck uses pneumatic or solid tires.

Check:

Front tire size
Rear tire size
Number of front and rear tires
Pneumatic or solid configuration
Loaded front and rear axle weights
Actual working surface

For very heavy forklifts, these specifications belong together.

A tire arrangement that works well on a reinforced industrial yard may not automatically be the correct choice for a platform with strict floor-loading limits.

When configuring a heavy duty forklift, tire selection cannot be separated from the axle load and overall truck design.

As capacity increases, the front axle may need to support a very large proportion of the loaded machine weight.

The tire arrangement therefore needs to match:

the axle + the truck weight + the cargo + the working surface.

That is more useful than simply saying:

"More tires are stronger."

Dual front tires are an engineering solution to a particular load condition, not an upgrade that should be added independently.

Many heavy duty forklifts use dual front tires because the front axle carries a very high load when cargo is on the forks.

Using four front tires allows that axle load to be distributed across more tires and gives the manufacturer another way to match the tire system to the required working condition.

But dual tires should always be considered together with:

axle load, tire rating, tire size, inflation pressure, truck design and ground conditions.

So when you see 4X / 2 on a high-capacity forklift specification sheet, it is more than a wheel count.

It tells you something about how the forklift's drivetrain and load-bearing system have been configured for heavy work.

References

• Hyster - H155–170FTS Series Specifications: 4X/2 Wheel Configuration.
• Hyster - 8–10T XT Series: Dual Front Tyre Capacity Data.
• Michelin - X-STACKER Industrial Tire Technical Data: Load, Pressure and Minimum Dual Spacing.
• Continental - Material Handling Tires Technical Data Book.
• Propolift - Why Does Axle Load Matter on a Heavy Duty Forklift?