4ePikanini wrote:get soft shocks for the front (and spacers from Uys on 4x4com forum if you want a lift) and hard shocks for the rear. That way you can tow heavy but the front is still comfy.
You can then get soft shocks as a standby set for the rear (if you want to have a soft ride on non towing trips) as the rear shocks can be changed in under an hour.
Fitting rear dampers with a higher damping coefficient will improve the heavy towing characteristics of a vehicle but I do not believe that it is a complete solution for heavy towing.
The reason why dampers with a higher damping coefficient will improve towing:
Consider the following single degree of freedom system:
- Force Diagram.jpg (5.48 KiB) Viewed 1102 times
Where
K = spring constant or spring rate (kN/mm)
X = Displacement of system caused by external force
C = Damping Coefficient of Damper
V = Velocity of movement caused by external force
The forces acting against the external force, F is KX and CV, where KX is the force generated by the displacement acting in on the spring and CV is the force generated by negative velocity acting on the damper.
You essentially get four types of single degree of freedom systems applicable to this explanation:
Undamped: ç = 0 When F is applied the object will vibrate at its natural frequency (Harmonic Oscillation)
Underdamped: 0< ç <1 When F is applied the object will vibrate with an oscillatory motion with an amplitude that decrease exponentially.
Criticaly damped: ç = 1 When F is applied the object will experience displacement but the motion is aperiodic and and the motion will diminish to zero.
Overdamped: ç > 1 When F is applied the object will experience displacement and the motion is also aperiodic, but the motion will diminish exponentially which means that it will take longer to return to the initial position.
Where ç = C/Cc C = Damping Coefficient for a system
Cc = Critical Damping Coefficient
Towing or heavy loading
When going over a bump or obstacle on the road the load or trailer being towed will increase the downward force acting on the suspension, and the graph of an underdamped system will follow an Oscillatory Motion until all the energy is dissipated. Stock standard suspension will probably be designed for peak performance with about half the maximum load being applied. If that is the case stock standard suspension can be seen as underdamped in maximum load applications. Therefore stock standard dampers might not be the best answer for heavy towing, and dampers with a higher damping coefficient will work better as suggested by 4ePikanini.
The reason why dampers with a higher damping coefficient will is not the only answer to heavy towing:
When a force F is applied to a single degree of freedom system, the counter force of the suspension can be described as follow:
F = - CV – KX
When towing on a smooth road the downward velocity is zero most of the time, and this will cause that the counter force is only generated by the spring, up to a point where the displacement of the spring generate enough force to balance the forces.
This means that with heavy towing the vehicle will be “nose in the air” under heavy towing as the “stiffer” dampers have no influence on the sag of the suspension.
Therefore for a complete solution for heavy loading/towing the spring constant needs to be increased by fitting stiffer springs or air helpers. But remember air helpers add to the damping coefficient as well, as air is not only a spring but a damper as well.
I am in the lucky position that the stock KYB dampers and Mitsubishi springs are perfect for my application, as I drive a Gen 3 SWB and my overlanding equipment have a combined mass of less than 400kg.