Cardan shaft park brakes (also known as driveshaft park brakes) are fitted to many small to medium trucks and a small number of passenger service vehicles.
They are designed to hold the vehicle and its load but have limitations which can lead to a vehicle rolling away.
There have been several incidents where the Cardan shaft park brake has failed and the vehicle has rolled away. In the last 10 years four of these incidents have resulted in fatalities, and we are aware of other unreported incidents.
A Safety Alert has been issued about how and why these brakes can fail. This sheet can be downloaded and supplied to vehicle owners and drivers.
It is important that owners and drivers understand how these park brakes are designed, how they function and how they should be used. Mechanics must be able to correctly diagnose, maintain and adjust these systems to the manufacturer’s specifications.
On this page, you can find out more information about these park brake types, how to maintain them and how to operate them safely.
Photo courtesy of TR Group
What is a Cardan shaft park brake
Cardan shaft park brake units are relatively simple in construction however safety risks can result from a lack of understanding about how to operate and maintain the brake correctly.
Cardan shaft park brakes use a foundation brake system, generally a single drum brake unit mounted to the gearbox housing. This acts directly on the driveshaft of the vehicle to provide the park brake function.
This type of park brake system brake usually consists of:
a lever mounted to the floor or dashboard within easy reach of the driver – this provides the operating force
a linkage or cable system running from the lever to the brake unit
an actuator connected to the linkage or cable system. This transfers the operating force to the brake
friction material attached to the brake shoes or disc pads to provide the holding power
a drum unit with a friction surface for the friction material to act on, bolted directly to the drive shaft
generally, there will also be a device or mechanism to adjust the foundation brake and cable or linkages, there may also be an inspection port to check the condition of the brake.
How to operate your vehicle safely
Due to the design of the brake, the vehicle is more prone to roll away when parked on a slope, especially if the load is changing and/or the vehicle is parked on an unstable surface.
Operators should avoid parking on slopes or use wheel chocks when parked on a slope and when the vehicle is jacked.
Operators need to understand the brake mechanism and its limitations.
Vehicle owners are responsible for ensuring the brake is serviced regularly to maintain performance.
Owners should also make sure that:
the parking brake is regularly maintained and adjusted in accordance with the manufacturer’s instructions
the parking brake is regularly inspected to ensure that it is not being contaminated by oil leaks from the engine or gearbox.
a set of chocks is available in the vehicle for use.
How do I park my vehicle safely?
Vehicles can roll away on a slope and there is no guarantee the brake will hold if the load changes.
Avoid parking on slopes or use wheel chocks when parked on a slope and when the vehicle is jacked.
Using wheel chocks:
Stop the vehicle, firmly apply the parking brake but continue to hold the vehicle stationary using the foot brake.
Have another person install chocks in front of or behind the rear wheels (depending on vehicles direction on the slope).
The person installing the chocks must avoid putting themselves in a position where they are vulnerable to any vehicle movement.
To remove the chocks, move the vehicle clear of the chocks then have another person pick them up and store them in the vehicle, while the driver holds the vehicle stationary using the foot brake.
Leaving the vehicle in gear and/or turning the front wheels to the kerb may help, but on its own may not prevent a vehicle from rolling away.
The park brake lever pull force required increases with slope and additional weight on the vehicle, therefore it is important sufficient force is used when applying the brake. This differs from other park brake systems where the maximum braking power is available each and every time the parking brake is activated.
The vehicle should not be parked on surfaces that do not provide good grip for the tyres, such as gravel, mud or snow as slippage of one wheel can allow the other wheel to turn which could result in the vehicle rolling away.
Towing another vehicle or trailer will exceed the holding capacity of the park brake so it must not be used to hold both vehicles on any surface.
Engaging the brake properly
The park brake must be fully engaged to the manufacturer’s recommended setting. The park brake lever may require more force than a driver is used to, especially if they don’t drive a vehicle with this type of park brake regularly.
If the weight of the vehicle is increased through loading, the amount of braking initially applied may not be enough to hold the heavier vehicle and it may roll away. These types of vehicles are designed to carry heavy loads and when loaded the weight may be over double the unloaded weight.
Don’t engage the park brake while the vehicle is moving at speed as this may damage it. This damage is unlikely to be obvious. Please note, when the vehicle is tested on the Roller Brake Machine the rollers are moving very slowly (3kph). This is not considered enough to damage the brake in any way.
What does good maintenance look like?
The location of Cardan shaft brakes makes them susceptible to contamination, especially from a leaking gearbox output seal. Contamination degrades the effectiveness of the brake and this will not be visible.
Keeping to the maintenance schedule and adjustment techniques recommended by the manufacturer will help the brake’s performance. Likewise, inadequate maintenance and poor brake adjustment will substantially degrade the performance of the parking brake system .
The key areas to focus your maintenance on are the:
foundation brake
actuation system (cables/levers)
adjustment.
How to maintain Cardan shaft brakes
The key to an effective Cardan shaft park brake performance relies on keeping to the maintenance schedule and adjustment techniques recommended by the manufacturer. Remember that this park brake is a separate unit and not connected to the service brake system.
Poor park brake performance due to wear, misalignment or damage of the brake mechanism will lead to low clamping forces available to hold the vehicle. Poor brake performance due to contaminated friction material (dirt, grease etc) getting into the system will lead to a loss of friction between the brake components. Poor brake performance due to incorrectly adjusted components will lead to a low application force and poor friction between the brake shoe/pad and the brake drum/disc.
We recommend you have this work completed by a heavy vehicle service provider or qualified technician. However, this information may be useful for large operators with in-house service personnel.
Foundation brake
Check the friction material for contamination and wear and check all other components operate correctly.
Check the drum or disc rotor for wear, excessively deep grooves, contamination, signs of overheating or excessive corrosion that could affect performance. Consider resurfacing or replacement.
Check the mountings for security, misalignment or other damage.
Actuation system
Check linkages for excessive wear and or cables for stretch or seizure.
Check for aftermarket adjusters fitted to the cable, if they are fitted the cable could be stretched and should be replaced.
Check the lever and ratchet operation is smooth and locks correctly.
Check any other pivot pins, pulleys, levers, mountings and attachments for wear, excessive corrosion, misalignment and other damage.
Lubricate all components as required by the manufacturer.
Adjustment
Always start by releasing the linkage or cable at the actuator so that the foundation brake can be adjusted correctly.
Ensure the brake shoes or pads contact the friction surface square on and flat against the drum or disc, adjust so there is a small amount of running clearance, but that it is not binding.
Re-attach the linkage or cable and adjust to give approximately 6-10 clicks of the ratchet at the lever. Always check the manufacturer’s setting
Carry out a stall test with the vehicle loaded if possible. Alternatively, find a 1 in 5 gradient and ensure the brake is effective in holding the vehicle in both directions.
Repeat checks and adjustment at every scheduled service.
Cardan shaft park brakes are tested for a certificate of fitness (CoF).
As of 1 December 2022, the CoF test for vehicles with Cardan shaft brakes is conducted using the roller brake machine. The test will apply to most classes of vehicle with Cardan shaft brakes. For more information, refer to the NZ Heavy Vehicle Brake Test Protocol(external link)
CoF requirements will also be updated to make it mandatory to have a warning sticker displayed in the cab of vehicles with Cardan shaft brakes from 1 April 2023. These stickers will be applied by testing stations free of charge when vehicles are presented for their CoF. Vehicle owners do not need to source their own stickers.
It is the owner’s responsibility to ensure the park brake is kept in good condition through maintenance. Owners and drivers should not assume that a current Certificate of Fitness (CoF) ensures the brake will be fully operational in all circumstances.
If your park brake fails the test you may be asked to have the brake serviced and to supply a statement of compliance (4085D form) prior to submitting the vehicle for a re-test.
Video: Testing cardan shaft brakes using a roller brake machine
