Explaining Advanced Ride Technology – A.R.T.

July 25, 2010

A.R.T. Overview:

Norco’s Advanced Ride Technology (ART) is an optimization of the proven FSR suspension system which delivers a more efficient pedaling and improved square edge bump compliant ride than ever before. This has been achieved by changing the location of the pivot points to achieve more chain growth and a more rearward axle path. The increased chain growth results in higher anti-squat characteristics which reduces suspension bob, making the bike pedal efficiently. The rearward axle path lets the rear wheel move back at the same time as it moves up to get out of the way of large, square edge bumps more effectively, allowing the bike to roll smoother and faster over rough terrain.

1. Improved Square Edge Bump Compliance
This refers to the suspension absorbing tall bumps where there is rearwards force put on the wheel in addition to vertical force. Figure 3. illustrates the forces involved in a square edge bump. If the wheelpath is rearward, the wheel can move backwards and upwards at the same time to get out of the way of the bump more quickly and efficiently. This allows the bike to roll much smoother and faster over bumpy terrain.

2. Increased pedaling efficiency
When a bicycle accelerates forward, inertia pulls the rider’s weight towards the back which results in compression of the rear suspension. This is known as squat. ART suspension is designed so that when the suspension compresses, the chainstay length increases. This is known as chain growth. When the rider puts force on the pedals, the chain becomes very tight and the bicycle will accelerate forward. The chain tension will also force the suspension to extend. This extension force is known as the anti-squat force because it counteracts the squat caused by the acceleration. With 30% more chain growth than before, ART suspension is designed to resist squat forces and reduce pedal bob, resulting in a highly efficient pedaling platform.

3. Improved Leverage Ratio Curve
A.R..T suspension uses a lower and more progressive leverage ratio to increase the bottom out resistance and improve the tuneability of the suspension. Lowering the leverage ratio reduces the amount of force on the shock which gives the shock greater control of the suspension movement. The adjustment dials on the shock will also have a greater effect on suspension performance, allowing the rider to fine tune the suspension to their liking. A more progressive leverage ratio makes the suspension get stiffer as it gets farther into its travel, giving the suspension that ‘bottomless’ feel.

Leverage Ratio Chart

Suspension Sag Adjustment

March 24, 2009

Recently I posted an overview on air suspension setup which spurred on a flurry of questions about sag. First of all what is sag? and how do I set it up for my riding style?

Sag is the amount of suspension that is used simply by sitting on the bike in a neutral position. This is the amount of shock compression while your body weight is centered over the front a rear suspension.

So, how to you set it up? Depending on your riding style, the amount of sag which is optimum will differ. Personally, I run about 20% on an XC bike and 30% on a DH/FR bike. For the purpose of this demonstration I have used a 2009 Norco Shore 1. The Shore has 7″ of rear travel so 30% sag is equal to 2.1″.

The First step in sag setup involves measuring the height of the bike from a reference point. I like to use the distance from underside of the saddle to the ground. In this case the height measured 35″. The bike has a total of 7″ of travel so when fully compressed this length will decrease to 28″. With 30% sag, the measurement will be slightly under 33″

If you are using an air shock then you can adjust your sag with your air pressure. Increasing air pressure will decrease sag while decreasing pressure will increase sag. If on the other hand you are using a coil shock, you will need to change your spring weight to alter sag.

I hope this clears things up a bit.

Dustan

Shock Adjustment – What does it do?

February 19, 2009

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

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.

Dustan

Bicycle Suspension – Part 4 – VPP vs DW-Link

January 20, 2009

The Virtual Pivot Point (VPP) and DW-Link are two relatively new suspension designs on the market. They both offer great benefits in ride quality over other, simpler designs but also have a few downfalls that will be discussed.

The two designs look very similar to one another, but are in fact quite different. Both designs use two links which connect the front and rear triangles of the bike. This allows the rear wheel to move independently of the frame in a close to vertical, sometimes rearward wheel path. The differences come in the way the links are positioned. Looking closely at the linkage, as the bike moves through its travel you will notice that the two links rotate in the same direction on a DW-Link while they are opposing on a VPP design. What this results in is a progressive vs. regressive leverage ratio. In English, a progressive ratio means that the further into the travel you are the harder it will be to further compress the shock (lower leverage ratio). On the contrary, a regressive ratio will get easier to compress as you move through the travel (higher leverage ratio).

Have a look at the two designs, they look similar, but are distinctly different.

Dustan

VPP - Regressive Ratio

DW-Link - Progressive Ratio

Bicycle Suspension – What does it mean? Part 1

January 8, 2009

Every year it seems that there is a new suspension design being released that is bo be the latest and greatest. What does all the techno-mumbo-jumbo mean? What is the difference between VPP and DW-Link? Rocker-Link and Horst-Link? Where does Single Pivot come in?

There is a lot of confusion here, what does this all mean? I will do my best to clear the air. Each suspension design has both benefits and detriments. There may not be a perfect design out there but there is one that is right for you.

In this upcoming series of posts, I will discuss Single Pivot, Rocker-Link, Horst-Link (FSR), VPP, and DW-Link designs. If you have any questions or comments about any of these technologies, please let us all hear your two cents. . . .

Dustan