Shock setup is to say the least, less than intuitive. . . .
The two most widely used types of air shocks on the market are Fox and Marzocchi, although they are based on different technology, adjustment is relatively similar. In this article I will go over the adjustment of a Fox DHX-5 and a Marzocchi Roco Air TST-R. If you are using a different shock the air pressures are similar to what I will mention but it is a good idea to consult your manual
On first inspection, the DHX and the Roco look quite similar. They both feature two air cartridges, a rebound knob and an Pedaling Efficiency Switch.
That is great. . .but – what do they do?
The main air cartridge is your main spring, this is the side mounted valve on the main body. The pressure in this valve will control the overall stiffness and sag on your bike. When setting up your shock, regardless of brand it is a good idea to start by inflating your body weight in air pressure. (if you weigh 170lbs, inflate to 170psi) From this base there is room for adjustment. In a Marzocchi shock you will likely let out air while a Fox will require increased pressure. Adjustment from this reference point should be made to adjust for optimal sag (usually between 20 and 30 percent) based on riding type.
The Second, smaller air cartridge will adjust how progressive the shock is. Simply, the more air you put in the assist valve, the harder it will be to bottom out. When setting up your bike, if unsure, make the two air-pressures equal and adjust from there.
On the Fox shock, you will also notice a knob called the bottom out adjustment. This knob controls the air volume in the boost valve. Wound all the way in is the lowest volume setting, where the bike will ramp up (get stiffer) late in the travel. Wound out, in the high volume setting the shock will ramp up slower through the entire length of the travel creating a more even feel.
Rebound adjustment will control how fast the shock ‘springs back’ after being compressed. The rebound knob is a small dial found at the base of the shock on the main body. When adjusting rebound there are two requirements to think about. The rebound should me slow enough that it does not give a bucking sensation and fast enough that it has decompressed fully before the next hit. Remember; when it comes to rebound, increasing rebound will equate to a slower return.
The Last adjustment on the shock is the Pedal Efficiency Switch. This adjustment is where you will find numerous confusing names which all pretty much mean the same thing. Fox calls their system ProPedal while Marzocchi uses TST. What are these adjustments? When engaged, the shock will have reduced pedal bob and be more efficient while climbing. To engage the switch move the pro-pedal to ‘Max’ position. On the Roco shock, rather than max/min, labels you will see CL and DS. CL is used while climbing while DS is used while descending. Simple enough?
It should also be noted that there are both min. and max. pressures for all shocks. Be sure to check labels and your owner’s manual as it can be potentially dangerous to be outside the recommended pressure range.
Your shock adjustment will not be perfect out of the box. The best way to dial it in is to throw a shock pump in your bag and hit the trails. Adjust it as you go.