Posts Tagged ‘pedal bob


Shock Adjustment – What does it do?

Bicycle suspension has become more and more complicated every year. In the store, your shock seemed great with knobs, valves and doofers coming out the ying-yang, the adjustability seemed limitless. Now, as you are in the moments before a ride trying to get the shock set up, the only thing limitless is confusion.

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

Roco TST-RFox DHX-5

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.

boost valve

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.



Bicycle Suspension – Part 2 – Single Pivot

The single pivot seems like a logical place to start when it comes to bicycle suspension. It is simple, it is versatile and it has been proven with years of use. As with all types of suspension it has both benefits and detriments. Which outweighs the other is your call.

The Single Pivot is the simplest of the suspension types on the mountain bike market. This fact alone is the first thing to like about the system. It is easy to manufacture, not much can go wrong and they can last nearly forever. On the negative though, they pivot on an arc that directly corresponds to the length of the swing-arm and the main pivot location.

What does this mean while riding? Bikes that use a single pivot are subject to fairly extensive compressive-brake jack. This means that under braking force the shock will compress and limit the functionality of the suspension. The bike may feel rigid and jerky while braking. The second issue is with pedaling. In low gears, the alignment of the pedaling force will pull the cranks and cassette together compressing the shock. This will correspond with significant pedal bob while in low gears. In higher gears, the chain is improved and better aligned with the swingarm minimizing the effect.

As you can see, single pivot has the benifit of being simple and inexpensive but at the cost of pedalability. What do you think?


Single Pivot

Single Pivot


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