Braking systems – Cables versus Hydraulics
All our braked Spitfire trailers are all fitted with hydraulically operated disc brakes. We’re often asked why this is the case… and why don’t we use cable brakes.
First off – there’s nothing wrong with cable-operated brakes. There are simply differences, advantages, and disadvantages between these braking systems.
Key components of each cable and hydraulic systems include:
The actuator: Whether Hydraulic or Cable, brakes on trailers under 2000kg GTM are almost all operated via a spring-loaded inertia driven piston, connecting to a small hydraulic master cylinder or cable crank. When the car brakes, the trailer inertia pushes against the tow ball to cause the piston to move proportionally against its spring – thereby activating the braking system via hydraulics or a cable.
For trailers over 2000kg GTM, the actuators are required to be self-powered in the event of a trailer break-away incident. On account of the braking forces required on heavier trailers, most systems in this category operate the brake callipers hydraulically.
Cables and hydraulic lines are critical components of an effective braking system. Both can be damaged during towing caused by stones and flying objects flicked up from the wheels. Other common damage is caused by snagging. Both cables and hoses can be protected from impact and corrosion by a variety of sheaths and braids from plastic to stainless steel. Boat trailer cables are prone to rusting out and are ideally made from stainless steel. Hydraulic hoses use braiding and stainless steel is a recommended option in this case
Cables and hydraulic lines are critical components of an effective braking system. Both can be damaged during towing caused by stones and flying objects flicked up from the wheels. Other common damage is caused by snagging. Both cables and hoses can be protected from impact and corrosion by a variety of sheaths and braids from plastic to stainless steel. Boat trailer cables are prone to rusting out and are ideally made from stainless steel. Hydraulic hoses use braiding and stainless steel is a recommended option in this case
Below are some considerations of each system:
Hydraulic Braking system
These are generally more efficient although also more costly braking systems than cable. Their operation is also more sensitive and less movement of the coupling piston through inertia is required to activate the brakes effectively, giving rise to more effective proportional braking. Hydraulic system couplings generally utilise heavier piston springs to restrict the inertial movement that could potentially damage the master cylinder, pushrods, etc
Hydraulic systems comprise more precise parts and components and these present greater challenges when subjected to extreme conditions of salt-water immersion, sand, and grit.
Hydraulic systems are also dependent on hydraulic fluid and a closed system that ensures instant and effective distribution of pressure to the callipers. Fluids used must be synthetic and non-hydroscopic as absorption of water into the fluid can lead to internal corrosion and seizure of master and slave cylinders at a critical time.
Cable Braking system
These are generally simpler, cheaper, and more robust than hydraulic braking systems. But this is not without limitations. The mechanics of pulleys, levers, and stretching cables is less precise and requires more inertial movement for effective operation compared to a closed hydraulic pressure system.
The callipers are a simpler construction than precisely engineered pistons and cylinders, and with effective lubrication and maintenance, will operate effectively in most conditions.
While generally hydraulic brake systems require only regular top up of fluid, and between top-ups the system continues to operate at consistent performance levels, cables will start to stretch from the first use of the system – therefore resulting in a slow but deteriorating brake performance between maintenance intervals. This is also exacerbated by brake pad wear for which the only compensation is to re-tighten the cables.
Cables are external to a brake calliper and therefore the movement of a calliper attached to an axle under varying loads will result in pull and release forces on the cables, effectively continually applying and releasing brakes during travel.
Why do we use hydraulic braking on our trailers?
Primarily for safety – We believe that most people do not attend to their stretched cables and therefore many trailers are on our roads with ineffective braking systems. On the contrary, provided there is fluid in the hydraulics and no air in the system, hydraulic brakes will continue to operate consistently and safely.
Our choice – We have to use hydraulics for the larger trailers in our range and therefore see it as more efficient to apply these systems as standard across the range.
The choice is yours…
Happy Boating
Andrew van Ryneveld
Spitfire Aluminium Boat Trailers
