How To Adjust Front Suspension On Mountain Bike

Are you bottoming out, packing up or bobbing? If you are or if you don’t know what it means, you might like to read this article where we take a look at how to adjust front suspension on mountain bike. Adjustable front suspension means just that – it’s adjustable.

To fully access the potential of your front shocks you will need to set up your sag and rebound damping and that’s what we’re going to help you with. It is important to note that some entry level suspension forks have limited adjustment as they are solely designed to make leisure and commuting rides more comfortable. The suspension in these forks are just springs.

If you feel that you need more control, then consider buying different forks with more available adjustment. This means that it can be set up to suit the rider and the terrain.

Performance suspension, on the other hand, is designed to give you more control on the trail. In order to get the full advantage of your forks, they have to be set up and adjusted correctly. To do this you will need to set up the sag and rebound damping. 

How To Adjust Front Suspension On Mountain Bike Part 1 – Sag

What is sag on a mountain bike?

Suspension sag is a distance of how much the front suspension compresses when the weight of the rider, including any gear carried, (hydration bag, helmet, spares etc.) is applied. 

Setting the correct sag allows the fork suspension to work most efficiently. Most manufacturers recommend between 15% and 25% sag. Too much sag means you are absorbing too much travel before you hit your first obstacle. This may cause bottoming out. Too little sag means that you’re not utilising the full travel.

To set up sag you will need:

A shock pump- This differs from a tyre pump because it delivers higher pressure and less volume. Note that your everyday pump will not work. 

Ruler– This is required to take measurements of your suspension.

Cable tie- This is in case you don’t have an O Ring.

Piece of paper and pen / calculator– They will be essential to work out the correct sag.

You can set up sag with the help of another person or like in this example by using a wall or bench.  

Setting up sag method

Step 1:

First make sure that your suspension is unlocked.

Check to see if there is a thin rubber ring on one of the stanchions.  This is the “O” ring.  

If there isn’t one then put a zip tie around the stanchion and tighten it so that it is firm but can still slide up and down. 

Step 2:

While the helper holds the bike at the front or while you are leaning against the wall apply either one of the brakes

and stand with both feet on the pedals. Bounce up and down a few times to break the stiction and stand on the pedals leaning on the forks.

Now move the “O” ring or zip tie to the bottom of the stanchion.

Step 3:

Get off the bike carefully without further compressing the fork.

Step 4: 

Now you can calculate your current sag. If your forks have markings on the stanchions, then have a look at the measurements. They will show the current sag.  

If there are no markings, then it’s time to do the calculations. To do this you will first need to know the front suspension travel. You can find this information on the suspension manufacturer’s website Rockshox or Fox . Find the serial number or I.D. code on the fork, this is usually marked on the back or on the lower leg.

For the Rockshox website press the GET STARTED button here:

Type the code here:

and the travel is shown here:

For the Fox website type your code here:

and the travel is shown here.

Once you know the travel, write it down on the piece of paper.

Step 5:

Now, using the ruler, measure the distance in millimetres between the “O” ring and the point where the stanchions meet the lowers on the fork.

Step 6:

Let’s do the calculation. So in this case the current sag is 35mm.

Now let’s divide that by the travel which is 120mm. It equals 0.292mm.

Finally let’s multiply this by 100 to give the percentage. The sag on this bike is 29% which is above the recommendation. 

To reach the desired percentage between 15% and 25% some air needs to be added. Adding or releasing 10PSI at a time is advised.

Now it’s time to recheck the sag. If there’s still too much sag then keep adding some more air. If there’s not enough sag then release some of the air using the button on the shock pump. Repeat the process until you reach the recommended percentage.

How To Adjust Front Suspension On Mountain Bike Part 2- Rebound Damping

What is Rebound Damping?

Rebound is the suspension returning to its original position. Damping controls the rate at which the suspension returns. The amount of rebound depends on the type of terrain. A series of small bumps need the suspension to rebound quickly between them.  If the rebound is too slow then the suspension might not return quickly enough to be able to take the next hit.

While going over bumps the suspension will keep compressing the suspension without time for it to return, squashing the unit more and more and not taking advantage of the full range of travel.  Rebound that is too fast creates the effect of a recoiling spring and can make the bike leave the ground and the rider can lose control. Terrain that includes big bumps and/or drop offs needs a slow return. The harder the landing the more your suspension will compress.  A fast rebound from full or nearly full compression will push the bike quickly to its original position and could cause the rider to lose control.  You will need to experiment with the type of environment in which you are riding.

Rebound damping is normally controlled by a small lever on the underside of the drive side lower which has a number of clicks.  Each click alters the speed of the rebound. To increase the rebound turn the lever clockwise and to decrease it turn it anticlockwise. Turn it a few clicks at a time and then check the rebound. The aim is to have the rebound returning fast enough to recover after a hit but not so fast that the bike leaves the ground and loses traction.

Setting up rebound damping method 1.

How to set up rebound damping?

If you have a Rockshox suspension unit then there will be pictures of a hare and a tortoise. Fox shocks have a “+” or a “-“. Move the lever towards the hare or the “+”. This is the fastest rebound.
Step 1
Make sure that your sag is set up correctly. 

Step 2
The aim to adjust the lever so that the rebound speed is the fastest possible without bouncing up and down. Stand to the side of the bike with both your hands on the saddle but not gripping. Push down hard and let the bike spring up. If the bike bounces off the floor, then the suspension rebound is too fast. Move the lever towards the “-” and try again. 

Step 3
Keep adjusting it so that it doesn’t bounce. 
Now you have reached critical damping and you will probably find that this works for most of your riding. 

Setting up rebound damping method 2

How do I set up rebound damping?

Step 1
Make sure that the sag is set up correctly.

Step 2
Find a high kerb. 

Step 3
Set the adjuster for the fastest rebound. This means that when you come off a bump the suspension will compress, then rebound past the sag, compress again, rebound past the sag and continue to do so 2 or 3 times, giving a trampoline effect. The aim to dial the rebound so that the rebound speed is the fastest possible without trampolining. 

Step 4
Now, seated on the bike and without pedalling, drop off the kerb. See how much bouncing goes on.  Dial the lever about half way. Ride off the kerb again.  How many times do you bounce? If you don’t bounce at all move the lever 2 notches towards the fastest rebound.  If you are still bouncing move the lever 2 clicks towards the slowest rebound. 

When you have found the point with the fastest rebound and no bouncing you have reached critical damping. You will probably find that this works for most of your riding.  The critical damping is set at the slowest speed without bouncing, and shock manufacturers recommend only adjusting three clicks towards the fastest rebound to ensure that you get the best range of suspension from the shock.

Overview of front suspension adjustment on mountain bike

Hopefully now you know how to adjust front suspension on mountain bike. Each cyclist, bike and trail conditions are different. Therefore it’s important to note that adjustment of sag and rebound damping is an individual preference. We hope this tutorial will help you get started, check out our video guide to see more. you can read about how to adjust rear suspension on a mountain bike in our previous post.

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