Before you hit the trails, you’ll want to ensure your suspension is correctly set up. When set too hard, you’ll experience that harsh bone-shaking descent no one wants. Too soft, and it’ll bottom out too easily, and the lack of responsive control will make the bike difficult to handle on rough terrain. Let’s take a look at just how to achieve the ideal mountain bike suspension setup.
Dial in the ideal mountain bike suspension setup

Modern mountain bikes come with either air shocks or coils shocks, and at Decathlon we stock a wide range of both. When it comes to setting the suspension system, there are three principle areas to focus on, namely sag, progression and rebound. When properly set up, you’ll experience a comfortable ride enabling you to get the most from your bike. Let’s take a deeper dive into each of these.
1. Setting sag on your MTB

Sag is defined as the travel the suspension uses under the total rider weight. Or in other words, how much it engages when you put your weight on the bike. Sag is the first thing you should set on your mountain bike, beginning with the rear suspension.

Setting the rear shock sag

To set the sag you need to:

  • Move the o-ring right up against the shock body in the zero position.
  • Gently place your weight on the saddle, being careful not to bounce. Ensure you’re wearing all your cycling gear, including your pack. The total weight should match your weight when cycling.
  • Check the travel which will be marked by the position of the o-ring. Many bikes will have a percentage marked on the shock, while on others you will have to measure manually. Aim for 30% sag on the rear shock.
  • With air shocks, if your sag is more than 30%, you’ll need to add more air with a shock pump. If it’s less, you’ll need to remove air. Note the pressure for future reference once complete.

Setting the fork sag

  • Push the o-ring fully down to the zero position.
  • Gently rolling and starting off in the seated position, stand up without bouncing the bike. Allow your weight to naturally push down from above the handlebars.
  • Aim for 25% sag on the front suspension. For air shocks, use a shock pump as necessary to adjust it.
2. Progression

While sag directly corresponds to how heavy the rider is, progression represents the force it takes for your suspension to bottom out, or in other words, use the full travel.

When riding on your chosen terrain you don’t want to use the full travel of the suspension.

Setting progression

  • Riding on flat ground, bounce as hard as you can. Use the o-rings to measure the travel.
  • Aim for 90% travel. You don’t want the front shock to bottom out entirely.
  • To fine tune, volume spacers can be added in or taken out. Add a volume spacer if you’re using all the travel. Remove a spacer if you’re not using enough.
  • If it still proves impossible to set the progression close to 90%, you can compensate with sag.
3. Rebound

Rebound, or damping, refers to how fast the suspension returns to sag after being compressed. You want this neither too fast nor too slow. Too fast, and the bike will react violently to bumps, while too slow and the shock won’t decompress fully before you hit the next bump resulting in a sluggish feel.

Ideally you want to hit the sweet spot, where the bike reacts to bumps without giving a bouncy ride. Let’s take a look at how to achieve this.

Setting rebound on the rear shock

  • Set rebound to the minimum value. Using a curb, and with your weight on the saddle, ride off it at walking pace.
  • Expect the suspension to return to sag once it decompresses. However, ideally it should overshoot sag very slightly before settling. Use the o-ring to verify that the shock overshoots sag.
  • Gradually increase the rebound setting one click at a time until you get to the point where it overshoots sag slightly before settling.

Setting rebound on the front fork

  • Begin with rebound at its lowest setting. Push down on the front fork using at least ⅓ of the travel with the brake engaged, and release quickly.
  • Upon release, the shock will decompress. Repeat this step while gradually increasing the rebound setting until you get to the point where the wheel begins to leave the ground upon rebound.
  • The ideal rebound setting will be just below the point where the wheel jumps off the ground upon decompression.
Further considerations - hardtail vs full-suspension bike

At this point, on a hardtail bike, the configuration is complete. However, on a full-suspension model there is one further check to carry out.

On the flat, while standing on the pedals, bounce the bike forcefully. Ensure that both the front and rear suspension return to sag at the same rate. If one returns faster than the other it can be dangerous on rough terrain. Tune the rebound accordingly to match both the front and rear shocks as closely as possible. If it proves impossible, err on the side of having the front suspension slightly faster than the rear.

In conclusion: The world of mountain biking can seem like one steep learning curve, but once you have configured the basics, you can tweak as you go.

The terrain you navigate will dictate the optimal suspension settings. And finding the sweet spot for a given terrain and riding style is where the secret lies.

Welcome to the cycling discipline that will test much more than just your legs! Mountain biking is one that’s constantly evolving and consistently pushing the boundaries for what’s possible.