Sag- not just for pants

Getting it right

“There is something to be gained by turning some dials.”  If knowledge is power, then we can acquire greater mastery over our bikes by learning a bit more about them.  Bike technology has exploded over the past decade, especially over the past few years with extremely capable, lightweight enduro bikes entering the market.  A higher degree of complexity has accompanied these trends, giving us the potential to create a truly customized ride experience. 

Your bike’s suspension is highly subjective, and most riders are not running the correct settings for their weight, riding style, and terrain.  This oversight sacrifices your bike’s capabilities, and most importantly, detracts from the fun you could be having.  What you believe to be a skill deficit could actually be overcome by turning a few dials and paying more attention to how your fork behaves in varying situations.  The time and effort you dedicate to setting up your bike correctly will pay dividends when it comes to how it rides, and your confidence on the trail.

In this series, we hope to arm you with more information about your suspension’s features and how to take advantage of what it has to offer.

Setup

The air pressure in your fork can be adjusted with a shock pump by unscrewing a cap on the top of the fork's crown.

The air pressure in your fork can be adjusted with a shock pump by unscrewing a cap on the top of the fork's crown.

Many of you have used a shock pump to adjust your fork’s air pressure.  In technical terms, you are actually changing the fork’s spring rate, which is the amount of force required to compress the fork a given amount.  The higher the air pressure, the more force that’s required to get the fork to work, and the stiffer the fork feels.  The opposite is also true.

If your fork is too soft, it will sit too far in its travel, lowering the ride height.  You will blow through your travel too easily when you hit bumps on the trail, and you’ll likely compensate with too much compression damping (more on that later).  If your air pressure is too high, the ride will be excessively harsh, feel unruly, and compromise traction.  The idea air pressure is somewhere in the middle.

Getting the air pressure right is the most important adjustment you can make, and has the greatest effect on the way your bike rides.  This will not only depend on your weight, but also on your riding style and terrain you ride the most.  The air pressure should be adjusted before you touch anything else on your fork.  A lot of people determine their air pressure by setting the fork’s sag. 

Sag

What is sag?  Sag is the amount that a fork compresses under the static weight of the rider.  It enables the bike to track over uneven terrain, basically allowing the front wheel to drop into depressions while maintaining contact with the dirt.  Wear all of your typical riding gear when you set your sag, including a full hydration pack.  Have a friend help you by holding the bike steady while you clip in, bounce around a couple times, and then assume your normal riding position, trying to imitate the way you distribute your weight between the front and back when actually riding (if your fork locks out, make sure it’s completely open).  In this position, have your friend slide the o-ring (or a zip tie) down the stanchion to the dust wiper, and then gently get off the bike without compressing the fork further. 

After sitting on your bike, get off carefully and measure the distance between the o-ring and the dust wiper on the left. The same idea applies to your fork.

After sitting on your bike, get off carefully and measure the distance between the o-ring and the dust wiper on the left. The same idea applies to your fork.

Sag is measured as a percentage of the total travel; measure the distance between the o-ring and the dust wiper.  You’ll have to consult your fork’s owner’s manual for its full travel, as this cannot be measure without dismantling it.  Once you know the fork’s travel, just divide the distance between the o-ring and dust wiper by the travel, and then multiply by 100 (or you can just eyeball it).  Voila sag. 

The right amount of sag will maximize your control and ability to conserve momentum over rough terrain.  Fork manufactures have sag recommendations depending on your weight, but you don’t have to follow them.  The rule of thumb for most trail riders is between 20 and 30% sag (which is to say, when you sit still on your bike, your fork compresses into 20-30% of its total travel).  But, these recommendations can be very misleading and can vary significantly depending on your riding style and frame geometry.

Rather than focus on sag when you’re meddling in the garage, set it to about 20% but then find out how much of your fork’s travel you actually use on the trail.  Push the o-ring down to the dust wiper, and then see how much it has moved after riding through the roughest terrain that you normally ride.  You want to use the most travel on the biggest hits, fastest, and most technical sections without bottoming out.  Ride with your shock pump and experiment until you’ve found the sweet spot.

Set up your suspension correctly and become a zen master on the trail.

Set up your suspension correctly and become a zen master on the trail.

This is the first in a series of installments from VIDA on how to understand your bike and get the most out of your equipment on the trail. Check back for more, or send us an email with specific questions.