Suspension 101: Part III - Damping
If you’ve read the last two parts to this series you should have a fundamental understanding of how air pressure and progression affect your ride, and also have the knowledge and confidence to make adjustments to your setup to better suit your suspension to your needs. Your suspension is smooth off the top with oodles of mid-stroke support and has enough ramp up to resist harsh bottom outs, while still letting you access full travel when you need it.
If you missed Part I: Sag, click HERE.
To catch up on Part II: Volume Spacers, click HERE.
In this, the third and final part of our Suspension 101 series, we’re going down the rabbit hole that is damping.
Fundamentally, damping is the means by which the suspension is controlled through compression and extension (rebound). Imagine a standard coil spring, if the spring is compressed with a weight and that weight is suddenly removed, the spring will return to its original shape as quickly as possible with fast, uncontrolled oscillations. This behaviour is the same for a coil spring or the air spring on your bike's suspension, and is known as undamped motion. If your mountain bike suspension was to behave like this it would feel very difficult to control, like a pogo stick. A damper controls both the compression and rebound of the suspension through its travel, smoothing out the harsh inputs into the suspension. It’s easiest to think of this as the damper adding resistance to the compression and rebound strokes, thereby resisting the spring’s movement in both directions.
A damper works to control the oscillation of your suspension by increasing the internal restriction of the system, adding resistance to the compression and rebound strokes. It does this by restricting the flow of oil through the damper. You can fine tune the internal restriction of the system by adding or removing compression and rebound damping. Adding more damping restricts the oil flow and removing damping allows the damping oil to flow more freely.
Well damped suspension increases control by keeping the tyre in contact with the trail as much as possible as well as giving a more stable ride with less fore-aft pitching from your bike.
The vast majority of modern suspension forks and shocks give adjustment over both the compression and rebound strokes, with high end models giving fine control over high and low speed compression and rebound. High/low speed refers to the speed of the fork or shock as it moves through its travel, not how fast the bike is travelling. A typical low speed event would be pumping through a turn, whereas a high speed event might be a harsh landing from a jump or drop. You could be travelling very fast down a trail and pump a turn, this translates to a relatively slow input into your suspension, activating the low speed circuits. The inverse is true for high speed damping. You could, for example, wheelie drop to a flat landing; low bike speed, high speed damping circuits.
So we understand the basics of how a damper controls the flow of oil in order to smooth out the ride and give us maximum traction when tackling technical terrain. But how do we adjust our suspension to make the most of its performance?
Let’s start at the front of the bike as it’s the wheel we rely on most for any changes in speed or direction, plus all the front wheel impacts go directly through our hands, so any improvements here will give us the biggest gains in terms of ride feel.
Beginning with a fork that has the correct amount of sag and number of volume spacers for your weight and riding style will allow you to make meaningful adjustments to your setup, and is really the most important and first step. If you’ve not already, go back and read Parts I & II of this series to understand the importance of sag and volume spacers.
Rebound damping controls the speed at which the wheel can return to the trail. A wheel which is in the air, i.e. just after a compression event, cannot be used to slow the bike down or change direction. Therefore, aiming to run your rebound damping as fast as you find comfortable gives the wheel the ability to stay in contact with the trail as much as possible. High speed rebound gives a controlled, damped return to full travel after a deep compression event. Running high speed rebound as fast as is comfortable allows the front wheel to stay in contact with the trail, but try and find your sweet spot between good return speed and control.
Having fast low speed rebound allows the front wheel to maintain contact with the trail over small chatter, giving that magic carpet, glued to the trail feeling. To summarise, a faster rebound speed allows the front wheel to return to the trail quickly, meaning that the wheel spends more time in contact with the trail generating more traction and giving more control.
Let’s move our attention to the compression damping of your fork, which controls the speed at which the fork can compress into its travel. A fork with a lot of compression damping is going to resist going into its travel, that impact force has to go somewhere and if the fork can’t soak it up it will be transferred to you. High speed compression provides support on big, fast impacts such as running your front wheel into a square edge. Running too much high speed compression will make it feel like the fork isn’t doing its job of soaking up these impacts, too little high speed compression and the fork might lack support on impacts such as these. Experiment with running as little high speed compression as possible, without losing that support.
Low speed compression is what holds your fork up in its travel as you pump around turns, or brake heavily on steep trails, but too much low speed compression stops your fork moving freely over small trail chatter. Again, find your balance of enough support without sacrificing sensitivity.
Now, hopefully, your front end is feeling planted and confidence inspiring. It can absorb small chatter without transferring lots of vibration to the bars and deals with deep compressions smoothly and with control. Moving on to the rear of the bike, follow the same steps as outlined for the fork but bear in mind that adjusting the rear will also affect the front. An important idea to keep in mind is that of the balance of the bike as a whole. Having sag, progression and damping closely matched front to back gives a bike that reacts similarly to impacts front to back, which will give you more confidence in how the bike is going to behave when you’re charging into technical sections.
Take note of your settings and go out and ride. Try and find an easily repeatable trail that you can consistently ride at close to your limit. Make changes to one setting at a time and try to simplify your thinking to “is this better or is this worse”. If you wound off two clicks of low speed compression and it feels better, take off another two and repeat the same better/worse thinking. This is a process known as bracketing, and can help you track changes to your bike and make meaningful adjustments.
Hopefully now you have the confidence to make complex changes to all aspects of your suspension. We’ve just scratched the surface here and the rabbit hole of suspension tuning and adjustment goes much much deeper. If the past three articles have piqued your interest and you want to learn more, please get in touch. Our dedicated suspension tech, Ady, over at TVB Tech runs pro level setup days with our Motion Instruments data logger which takes the guesswork out of setup.
Otherwise if you have more questions, feel free to swing by the shop on Innerleithen’s High Street to chat anything and everything suspension related.
01896 831429
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