If you’re interested in learning more about off-road suspensions, check out Jonathan Hanson’s excellent, in-depth article on Overland Tech & Travel (link below), check out the video above, or read the quick tutorial in this post. I’ve also included Jonathan’s recommendation on a 12-way adjustable shock that sounds like a great value.
How to shock absorbers work? Basically, they dampen the wheel’s up-and-down movement by forcing a valved piston through an oil-filled tube. Imagine forcing a piston, with tiny holes in it, through a tube of oil. It takes work. After a while you’d get tire and stop. The same thing happens to your wheel. It doesn’t want to do the work of forcing the piston through the oil either, so it stops bouncing up and down. The piston and oil basically absorb the energy of the wheel.
This absorbed energy turns into heat within the shock absorber. That heat makes the shock work less well, because a piston moves through hot oil more easily than it does through cold. And if the piston is moving a lot, like on a washboard road, the oil can get worked so hard that it foams. Hot, foamy oil doesn’t work in a shock at all.
There are two way shock manufactures address this problem:
1. Adding a high-pressure gas to shock, which keeps the oil from foaming. These are known as high-pressure, mono-tube shocks.
2. Adding low-pressure gas or foam to a shock and creating a tube-within-a tube design. These are known as low-pressure, twin-tube shocks. The oil is forced from an inner tube to a fatter, outer tube.
Old Man Emu Nitrocharger shocks, and Ironman Nitro-Gas, are both low-pressure, twin tube shocks.
Two other twin-tube shocks that Jonathan speaks highly of in his Overland Tech & Travel article are the Koni Twin-Tube Raid, a shock that’s unfortunately not available in the US except for certain G-wagen models, and the Boss 12-way adjustable shock, which is available in North America. The Boss shock employs a foam insert instead of gas, and offers 12-way adjustable valving. It seems quite nice to be able to compensate for extra weight in a truck by just tightening up the valving, and that on a shock that sells for CN$150.
The Boss shocks sound like they’re worth checking out.