Telehandler Stability Guide

Telehandler Stability at a Glance

Who Should Read This Guide?

This guide is useful for:

• New and experienced telehandler operators.
• Site supervisors and plant coordinators.
• Employers planning telehandler work.
• Operators using different attachments.
• Businesses operating on rough or changing ground.
• Agricultural telehandler users.
• Lift planners working with suspended loads.
• Managers investigating telehandler instability or near misses.

What You’ll Learn

This guide explains:

• How a telehandler maintains stability.
• Why lifting capacity changes as the boom moves.
• How load weight and load centre affect the machine.
• The risks created by slopes and poor ground.
• Why travel speed and steering technique matter.
• How tyres, attachments and stabilisers affect stability.
• What to do if the telehandler begins to overturn.
• Common operating habits that increase tip-over risk.

How Does a Telehandler Stay Stable?

A telehandler does not have unlimited lifting capacity.

Its ability to remain upright depends on the relationship between:

• The machine’s own weight.
• The load being handled.
• The attachment.
• The position of the boom.
• The distance of the load from the machine.
• The condition and angle of the supporting ground.

The machine effectively balances the forward force created by the load against the weight and geometry of the telehandler.

As the load moves farther away from the front axle, its leverage increases. This is why a telehandler may be capable of lifting a heavy pallet close to the machine but only a much lighter load at maximum forward reach.

The operator must use the approved load chart for the exact machine, attachment and configuration rather than relying on the telehandler’s maximum advertised capacity.

What Is the Stability Triangle?

The stability triangle is a useful basic explanation of how many lift trucks remain upright.

The machine’s support points form an area within which the combined centre of gravity should remain. On an ordinary four-wheel-steer telehandler, the effective stability area is influenced by the front axle and the pivot point of the oscillating rear axle.

As the machine turns, travels over uneven ground or handles an elevated load, the combined centre of gravity moves.

If it moves outside the stable supporting area, the telehandler can overturn.

The stability-triangle principle helps explain why:

• Raised loads make the machine less stable.
• Turning sharply can cause a sideways overturn.
• Uneven ground can shift weight onto one side.
• A load that is safe straight ahead may not remain safe during travel or turning.

The actual design and stability characteristics vary between telehandler models, so operators must follow the manufacturer’s instructions rather than relying solely on a general diagram.

Longitudinal and Lateral Stability

Telehandlers can lose stability in more than one direction.

Longitudinal stability

Longitudinal stability concerns tipping forwards or backwards.

A forward tip can occur when:

• The load is too heavy.
• The boom is extended too far.
• The load centre is greater than expected.
• The machine stops suddenly while travelling with a load.
• The attachment adds unaccounted weight.
• The ground beneath the front wheels gives way.

The approved load chart primarily helps the operator control forward stability during lifting.

Lateral stability

Lateral stability concerns overturning to either side.

A sideways overturn may result from:

• Turning too quickly.
• Travelling across a slope.
• Driving with the load raised.
• One wheel entering a hole or soft area.
• Sudden load swing.
• Incorrect tyre pressures.
• Steering sharply on uneven ground.
• Operating with a side-shifted or unbalanced load.

Load charts do not remove these risks. A load can be within the chart’s stated capacity while the machine remains unsafe because of travel speed, slope or ground conditions.

How Boom Extension Affects Stability

Extending the boom increases the horizontal distance between the machine and the load.

Even if the load itself does not become heavier, the overturning effect increases because it acts through a longer distance.

Consider holding a weight close to your body and then extending your arm. The weight has not changed, but it becomes harder to support.

The same principle applies to a telehandler.

As the boom extends:

• Available capacity normally decreases.
• The machine may become more sensitive to ground movement.
• Small boom movements can cause larger load movements.
• The operator has less margin for error.
• Sudden hydraulic movements can create dynamic forces.

The operator should use only as much boom extension as the task requires and should never “test” whether the machine can reach by continuing beyond the approved chart.

How Boom Height Affects Stability

Raising the boom lifts the combined centre of gravity.

A higher centre of gravity makes the telehandler more vulnerable to:

• Sideways slopes.
• Sharp steering.
• Uneven surfaces.
• Sudden braking.
• Load movement.
• Wind acting on large loads.

When travelling, loads should normally be kept at the manufacturer’s recommended travel height, generally as low as reasonably practicable while maintaining suitable ground clearance and visibility.

Travelling with a highly elevated load should be avoided unless the manufacturer’s instructions and an assessed operating method specifically permit it.

Understanding Load Weight

Operators need reliable information about the weight of the load.

It may be established using:

• Delivery documentation.
• Manufacturer labels.
• Packaging information.
• Engineering drawings.
• A verified weighing record.
• A suitable calculation completed by a competent person.

Visual estimation is unreliable.

A pallet of dry blocks may weigh considerably less than one that has absorbed rainwater. A container may hold residual material that is not obvious from the outside. An irregular component may also have a centre of gravity away from its geometric centre.

HSE guidance advises that lifting equipment must not be used where there is doubt about the load’s weight or the adequacy of the equipment.

What Is the Load Centre?

The load centre is the horizontal distance from the vertical face of the forks or attachment reference point to the load’s centre of gravity.

Telehandler capacity information is based on defined load centres.

A longer load moves its centre of gravity farther forward, even if its total weight remains unchanged.

Examples include:

• Long packs of timber.
• Pipes.
• Wide stillages.
• Machinery with weight concentrated at one end.
• Pallets not positioned fully against the fork carriage.
• Loads supported only on the fork tips.

Where the actual load centre exceeds the value used for the load chart, the chart’s stated capacity may no longer apply.

Loads should be positioned as close to the fork heel or carriage as their shape and handling method permit.

Why Load Charts Are Essential

A telehandler load chart shows what the machine can lift at different combinations of boom height and forward reach.

Depending on the model, the chart may also account for:

• Attachment type.
• Stabiliser position.
• Tyre specification.
• Fork load centre.
• Stationary or travelling duties.
• Machine configuration.

Before lifting, the operator should confirm:

1. The load weight.
2. The load centre.
3. The required lift height.
4. The required forward reach.
5. The attachment being used.
6. The correct chart for that combination.

The machine’s maximum capacity figure usually applies only in a limited configuration. It should not be interpreted as the weight that can be lifted at every height and reach.

Rated-Capacity Indicators and Warning Systems

Many telehandlers have a longitudinal load-moment indicator or rated-capacity warning system.

Depending on the machine, it may provide:

• Visual warnings.
• Audible alarms.
• Progressive capacity indication.
• Hydraulic movement restriction.
• Automatic cut-out of certain functions.

These systems are valuable but have limitations.

They do not normally confirm:

• That the load weight entered or assumed is correct.
• Whether the ground is suitable.
• Whether a side slope is safe.
• Whether the attachment is approved.
• Whether the operator is travelling too quickly.
• Whether tyre pressures are correct.
• Whether a suspended load is swinging.
• Whether the load chart matches the attachment.

Warning systems should be checked during the machine’s pre-use inspection and used in accordance with the manufacturer’s instructions. They must never be deliberately overridden or treated as a substitute for operator judgement.

Ground Conditions

Suitable ground is fundamental to telehandler stability.

The machine may overturn or become unsafe if the ground:

• Is soft or recently backfilled.
• Contains hidden voids.
• Has been weakened by rain.
• Is close to an excavation.
• Covers a basement, culvert or service chamber.
• Has an excessive slope or crossfall.
• Contains deep ruts or potholes.
• Cannot support the machine’s wheel or stabiliser loads.

Ground that appears firm at the start of a shift can deteriorate because of:

• Repeated machine movements.
• Rainfall.
• Excavation activity.
• Leaking services.
• Frost and thaw.
• Other heavy plant crossing the area.

The route and lifting position should be assessed before work begins and reviewed when conditions change. CPA guidance notes that telehandlers may need to be restricted to assessed travel routes and designated lifting areas where bearing capacity has been confirmed.

Working Near Excavations and Edges

Telehandlers should be kept a safe distance from:

• Trenches.
• Basement edges.
• Retaining walls.
• Embankments.
• Service excavations.
• Unprotected drops.
• Recently filled ground.

The weight of the machine can cause the edge to collapse, even where the wheels do not cross the visible excavation line.

The required distance depends on factors including:

• Excavation depth.
• Soil condition.
• Ground support.
• Machine weight.
• Wheel loading.
• Weather.
• Previous disturbance.

A fixed universal distance should not be guessed. The safe position should be established through suitable planning and, where necessary, competent ground or engineering advice.

Telehandlers on Slopes

Slopes greatly increase the risk of overturning.

The manufacturer’s maximum permitted gradient should never be treated as a recommended normal operating angle. It is a limit subject to defined machine conditions, not a target.

Before travelling on a slope, consider:

• The direction of travel.
• Whether the machine is loaded or unloaded.
• The position of the boom.
• Ground traction.
• Surface condition.
• Crossfall.
• Turning points.
• Braking ability.
• Manufacturer instructions.

Travelling up and down slopes

The correct orientation depends on the telehandler, load and manufacturer’s instructions. Operators should follow the manual and site method rather than applying a rule remembered from a different type of lift truck.

Travelling across slopes

Sideways travel across a gradient is particularly hazardous because it moves the machine’s centre of gravity towards the downhill side.

Where reasonably practicable, routes should be planned to avoid side slopes and steep, uneven or slippery surfaces. HSE workplace-transport guidance also advises selecting suitable routes and driving at a speed appropriate to the vehicle, load and ground conditions.

Speed, Steering and Braking

Dynamic forces can overturn a machine that appears stable while stationary.

Risk increases when the operator:

• Turns sharply.
• Travels too quickly.
• Brakes suddenly.
• Accelerates harshly.
• Changes direction abruptly.
• Steers while the boom is raised.
• Drives over kerbs, holes or debris.
• Attempts to correct load swing through machine movement.

Telehandlers should be driven smoothly at a speed suitable for:

• The load.
• Ground conditions.
• Visibility.
• Pedestrian activity.
• Turning radius.
• Weather.
• Machine configuration.

Slowing down before a turn is safer than braking heavily during the turn.

Tyres and Telehandler Stability

Tyres form part of the machine’s stability system.

The operator should check:

• Tyre pressure.
• Cuts and damage.
• Missing tread.
• Embedded objects.
• Sidewall condition.
• Wheel-nut security.
• Correct tyre type.
• Foam-filled or solid-tyre requirements.
• Equality between tyres on the same axle.

Incorrect tyre pressure can change how the machine sits and responds under load.

A telehandler should not be operated where:

• Tyre pressures are significantly unequal.
• A tyre is visibly damaged.
• An incorrect tyre type has been fitted.
• The tyre does not meet the manufacturer’s specification.
• Wheel fasteners are loose or missing.

Where foam-filled tyres are specified, they should not be replaced with pneumatic tyres without manufacturer approval and corresponding capacity information.

Four-Wheel Steering and Wheel Alignment

Telehandlers may offer steering modes such as:

• Front-wheel steering.
• Four-wheel coordinated steering.
• Crab steering.

The correct mode should be selected for the task and used according to the operator’s manual.

Before road travel or higher-speed movement, the wheels may need to be correctly realigned and the specified steering mode selected.

Misaligned wheels can cause:

• Unexpected machine movement.
• Increased tyre wear.
• Poor tracking.
• Difficulty controlling the machine.
• Instability during travel.

Operators should check the wheel-alignment indicator where fitted and visually confirm alignment when required.

Attachments and Stability

Every attachment affects the machine differently.

The attachment may alter:

• Total front-end weight.
• Load centre.
• Visibility.
• Carriage geometry.
• Capacity.
• Hydraulic behaviour.
• Load security.
• The applicable load chart.

Examples include:

• Buckets.
• Lifting jibs.
• Hooks.
• Bale clamps.
• Grabs.
• Sweepers.
• Fork extensions.

A physically compatible attachment is not automatically approved for the machine.

The operator should confirm:

• Manufacturer approval.
• Attachment identification and weight.
• Correct connection.
• Applicable load chart.
• Inspection condition.
• Any additional training requirement.

Fork extensions can move the load centre farther forward and should not be treated as a way to increase lifting capacity or handle loads that the standard forks cannot safely support.

Buckets and Loose Material

A telehandler bucket can introduce stability risks because the weight of loose material may be difficult to judge.

Volume alone does not establish weight.

For example:

• Wet soil is denser than dry woodchip.
• Mixed demolition material can contain unexpectedly heavy objects.
• Material can stick inside the bucket.
• A heaped bucket may place the centre of gravity farther forward.
• Sudden bucket movement can shift material dynamically.

The operator should avoid:

• Overfilling the bucket.
• Travelling with the bucket raised.
• Turning sharply.
• Using the telehandler like a loading shovel where it is not designed for that method.
• Striking a material face aggressively.
• Assuming every full bucket is within capacity.

Suspended Loads and Stability

A suspended load can swing independently of the machine and create dynamic forces.

Stability may be affected by:

• Sling length.
• Load shape.
• Wind.
• Steering.
• Braking.
• Boom movement.
• Route condition.
• Attachment position.
• Load swing.

The exact machine, attachment and configuration must be approved for suspended-load duties, and the lifting operation must be properly planned.

Standard fork-handling competence should not be assumed to cover suspended loads. NPORS provides a separate Telescopic Handler Suspended Loads Training category addressing the specialist knowledge and practical skills involved.

Stabilisers and Outriggers

Some telehandlers have front stabilisers or outriggers.

When correctly deployed, these may improve capacity in particular operating configurations. However, they only provide the benefit shown in the approved load chart when used exactly as specified.

Before deploying stabilisers, check:

• The ground is capable of supporting the imposed load.
• The feet are fully supported.
• Suitable spreader mats are used where required.
• The machine is positioned as instructed.
• The correct stabiliser load chart is selected.
• The stabilisers are fully deployed where the chart requires it.
• The area is clear of people and obstructions.

A stabiliser placed on a drain cover, soft verge or hidden void can punch through the surface and destabilise the machine.

Partial deployment should not be assumed to provide partial chart capacity unless specifically covered by the manufacturer’s information.

Load Security

A stable machine can still become unsafe if the load moves.

Loads should be:

• Correctly positioned on the forks.
• Supported over a suitable fork length.
• Placed against the fork heel where practicable.
• Balanced.
• Secured where required.
• Free from loose materials.
• Suitable for the intended route.

Particular care is needed with:

• Damaged pallets.
• Long loads.
• Uneven loads.
• Liquid containers.
• High stacked materials.
• Loads affected by wind.
• Materials with an offset centre of gravity.

Tilting the carriage back should not be used to compensate for a badly positioned, unstable or unsuitable load.

Visibility and Stability

Poor visibility can indirectly lead to overturning by preventing the operator from seeing:

• Potholes.
• Slopes.
• Excavation edges.
• Pedestrians.
• Overhead obstructions.
• Changes in ground level.
• Other vehicles.

Where the load blocks forward vision, the operator may need to:

• Travel in the safe direction specified by the manufacturer.
• Use a trained signaller.
• Select a different route.
• Reconfigure the load.
• Use another handling method.
• Stop until visibility can be restored.

Reversing should not be treated as an automatic solution where it introduces other risks.

Weather Conditions

Weather can alter both ground stability and load control.

Consider:

• Heavy rain softening the route.
• Ice reducing traction.
• Strong winds affecting elevated loads.
• Fog or darkness reducing visibility.
• Snow hiding ground defects.
• Frost followed by thaw weakening the surface.

Large or lightweight loads may be affected by wind even where their weight is within the machine’s capacity.

Operations should stop when conditions fall outside the manufacturer’s limits or the safe system of work.

Pre-Use Checks That Support Stability

Before operating, the telehandler should be inspected in accordance with the manufacturer’s instructions.

Stability-related checks include:

• Tyres and wheels.
• Steering.
• Brakes.
• Boom and carriage.
• Attachment locking.
• Hydraulic leaks.
• Stabiliser operation.
• Rated-capacity indicator.
• Boom-angle and extension indicators.
• Mirrors, cameras and visibility aids.
• Seat belt and restraint system.
• Warning devices.

Any defect that could affect safe operation should be reported and dealt with before the machine is used.

A thorough examination does not replace daily checks, maintenance or defect reporting.

What Should You Do If the Telehandler Starts to Overturn?

The operator should follow the manufacturer’s emergency instructions and training.

For a seated cab telehandler fitted with a restraint system, the generally recognised response is to:

• Remain in the cab.
• Keep the seat belt fastened.
• Brace yourself.
• Hold onto the steering wheel or suitable handholds.
• Lean away from the direction of overturn.
• Do not attempt to jump out.

Jumping can place the operator in the machine’s crushing zone.

This guidance assumes the machine is fitted with the required protective structure and restraint system. The operator should understand the emergency procedure for the specific telehandler before starting work.

Expert Tip from Vally Plant Training

When assessing a lift, do not ask only:

“Can the telehandler lift this weight?”

Ask:

1. Can it lift the load at the required reach and height?
2. Is the load centre within the chart?
3. Is the attachment approved?
4. Is the ground suitable for the machine and load?
5. Can the machine travel and turn safely?
6. Will the load remain secure and controlled?

Many overturns are caused by several small factors combining rather than one obvious overload.

Common Telehandler Stability Mistakes

Treating the maximum capacity as universal

The headline capacity normally applies only at limited boom positions.

Guessing the load weight

A load’s appearance does not reliably indicate its weight.

Ignoring the load centre

A long load may exceed the chart even when its total weight appears acceptable.

Travelling with the boom raised

This raises the centre of gravity and increases lateral instability.

Turning too quickly

Dynamic forces can move the combined centre of gravity outside the stable area.

Working too close to an excavation

The ground may collapse beneath the machine before a wheel reaches the visible edge.

Relying entirely on the capacity indicator

Electronic systems do not assess every ground, travel and attachment hazard.

Using the wrong attachment chart

The standard fork chart may not apply to a bucket, hook or jib.

Ignoring tyre pressure

Unequal or incorrect pressures can alter machine stability.

Continuing when conditions change

Rain, excavation work or repeated traffic can make a previously safe route unsuitable.

Related Telehandler Guides

Continue through the Telehandler Knowledge Hub:

• NPORS Telehandler Training Guide
• How Much Is a Telehandler Ticket?
• How to Become a Telehandler Operator
• Telehandler Licence Explained
• Telehandler Operator Salary Guide
• Telehandler Attachments Guide
• Telehandler Suspended Loads Guide
• Telehandler Load Charts Explained — coming soon
• Daily Telehandler Inspections Explained — coming soon

Related Plant Safety Guides

• Ground Conditions and Construction Plant
• Daily Plant Inspections Explained
• Working Around Pedestrians and Mobile Plant
• Safe Lifting Operations
• Plant Exclusion Zones Explained
• Working Near Excavations

Continue Your Training

Vally Plant Training provides both NPORS-accredited operator training and in-house certificated training across telehandlers and a broad range of plant categories.

Relevant options include:

• Telehandler Operator Training.
• Telescopic Handler Suspended Loads Training.
• Counterbalance Forklift Training.
• Slinger Signaller Training.
• Plant Operations NVQs.

Training can be delivered at our Tewkesbury training centre, where the appropriate machine and course are available, or on suitable customer sites throughout the UK.

On-site customers should provide a suitable machine, approved attachments, operator manuals, current inspection and examination documents, risk assessments and a safe training area.

About the Author

This guide has been prepared by the instructional team at Vally Plant Training, an NPORS Accredited Training Provider delivering training and assessment across plant machinery categories.

We also provide in-house certificated operator training where employers require instruction and assessment based on their own machines, attachments and workplace procedures.

The content reflects practical experience teaching operators how load charts, boom position, ground conditions, tyres, attachments and operating technique combine to affect telehandler stability.

This guide is reviewed when relevant HSE guidance, NPORS standards, manufacturer requirements or recognised industry practices change.

Important Information

This guide provides general safety information and does not replace:

• The manufacturer’s operator manual.
• The correct load chart.
• A suitable risk assessment.
• Ground assessment or engineering advice.
• Site traffic-management arrangements.
• Attachment-specific instructions.
• Formal operator training and familiarisation.

The safe capacity and operating method must be confirmed for the exact telehandler, attachment, load, ground conditions and task. Operators should only use machinery for which they have been properly trained, assessed and authorised.