Everything you need to know about how to set up your mountain bike suspension, including mountain bike fork, shock and coil shock suspension set up.
Need a bit of help with set up mountain bike suspension fork and shock (if you have one)? Set up is absolutely crucial in order to get maximum comfort and control while riding off-road. Get it wrong and you’ll be fighting a constant battle with your bike and the terrain. Get it right and you will enter a whole new world of control. And while it can seem very complicated, getting the basics right is actually simple. Read on and find out how to dial in your mountain bike suspension.
Here’s what we’re covering in this guide:
Jump to: Basic suspension theory – how does MTB suspension work?
Jump to: How to set the sag on mountain bike suspension
Jump to: How to set rebound damping on a mountain bike
Jump to: Rapha UK women’s clothing sale
Jump to: How to adjust spring progression in mountain bike suspension
Jump to: And finally, look after your suspension!
Basic suspension theory – how does MTB suspension work?
Mountain bike suspension is either via forks which control the movement of the front wheel, or forks and a shock which controls the rear wheel movement. These are essential pneumatic springs (or sometimes, in the case of shocks, actual springs) and it’s how these springs are tweaked to respond to the terrain, rider and environment that affects how well they perform.
With setting up suspension you are essentially setting two things: how hard the spring is and how that spring’s movement is controlled (the damping).
With air sprung suspension (which covers the vast majority of suspension these days), the firmness of the spring is dictated by the air pressure. Air pressure in an air chamber. If you need a harder or softer spring you adjust the pressure in this chamber with a shock pump.
For this guide we’re going to assume that you have air sprung suspension, but if you do have coil sprung suspension this guide is still worth reading as the principles are still relevant.
The spring’s movement – how it compresses and how it re-extends (rebounds) – is controlled by your suspension’s damping.
Damping is essentially fluid passing through a hole or over a series of metal shims (very thin washers). Fluid will move more slowly through a small hole than a larger hole, or over a thicker/stiffer shim than a thinner shim. With a larger hole, fluid will pass through faster. When you’re adjusting your damping, you’re changing the size of hole(s) that the fluid flows through.
How much control and adjustment you have over your suspension’s damping will depend on your fork or rear shock. Some forks and shocks only have rebound damping adjustment. Some forks and shocks have compression damping adjustment as well.
Some higher end forks and shocks have separate damping adjustments for low speed and high speed impacts/forces. We’ll deal with these later on in this guide.
How to set the sag on mountain bike suspension
This is first thing you need to do with your suspension. Thankfully it’s also the easiest thing you’ll need to do. You’ll need a specific shock pump for this.
What is sag? Sag simply refers to the position the bike settles into with a rider on board. It’s your starting point before fettling any other parameters. Begin with the rear suspension, assuming you have it.
While many guides advise you to set your sag in what’s often referred to as the ‘attack’ position, we’d suggest taking a seated approach. Why? It’s a little more repeatable than the standing position, it’s easier to do on your own, as you don’t need a helper to hold the bike, or a wall to lean against, and finally it’s less likely that your suspension will end up too soft when you’re seated and climbing, as that’s the position you use to set-up the bike.
Suspension is designed to work best with between 25-35% sag (AKA a quarter to a third). For example, on a 100mm travel bike you want to aim to have 25mm-33mm of sagged travel when you sit on your bike.
- Start by making sure any lockouts are off and your compression damping dial is open (unscrew counter-clockwise).
2. Drop your saddle and sit on the bike with your back straight, your legs planted on the ground and your arms holding the bars.
3. Bounce on the bike a little and let it settle.
4. Slide the o-ring on the shock up to the seal on the air can.
5. Lift your feet for a second so that your weight is running directly through your straight back to your saddle.
6. Stand up and step off the bike, making sure that you don’t compress the suspension further.
7. Check the distance from the main air seal to the o-ring. If you have a RockShox shock you can read the gradients to work out your sag percentage – aim for 30% to start with. If it’s another brand then measure the distance using a small ruler or tape measure.
8. Find out the shock stroke for your bike and divide by 3.3 to work out 30% sag. If your o-ring has gone beyond this point then you’ll need to add air, if it hasn’t reached it then you’ll need to remove air.
9. When adding or subtracting air remember to compress the suspension with the pump attached to equalise the positive and negative chambers before you recheck the sag. You can do this by putting your stomach on the saddle and pulling up on the swingarm.
10. Don’t check the sag with the pump attached as it will act as an extra air chamber.
11. Make a note of the pressure on your phone when you hit 30% sag so you can always get back to your baseline if you make changes.
12. When it comes to fork sag, we tend to go much more by feel than any specific percentage. Try starting with the recommended pressures printed on the chart on your fork, which will work out around 15-25%.
You want the bike to feel like the front and rear are moving up and down roughly the same amount when you bounce around in the car park.
Once riding, if you find you’re not getting decent amounts of travel used on big hits and landings then feel free to try increasing how much sag you’re running ie. let air of the suspension, try 10psi at a time. You should also dial off a click or two of rebound damping after you’ve let air out.
Many brands now have suspension set-up calculators to help you get started. These can be very useful, but always cross-check with your own sag measurements to see how accurate they are. Most ask you to input your height and weight and will give you a pressure for the shock and sometimes the fork. The more sophisticated calculators will also give you damper settings and volume spacer recommendations.
PRO TIP: Try to use the same pump when making changes to your shock pressure, as the gauge may read differently between pumps.
How to set rebound damping on a mountain bike
DO NOT attempt to set your rebound damping until you have set your sag properly!
If your bike has compression adjustment (blue dials) then unwind them completely (counterclockwise). The most important damping adjustment to get right (it’s also the most common adjustment on all forks and shocks) is rebound damping. This is the speed at which the fork or shock returns after hitting a bump. Most rebound dials are red and you’ll find them on the body of the shock and/or the base of the fork, by the dropout. Start by closing the rebound circuit completely (clockwise), then count the number of clicks to fully open (counterclockwise). That’s your range of adjustment.
- Set both your fork and your shock in the middle of the range and make a lap of the car park.
2. Bend your knees and elbows and compress the suspension as hard as possible, but as your body extends fully, keep your limbs straight.
3. Watch the fork and the shock – they should return just past the sag point, then settle at sag. If they extend beyond the sag point on the second compression then you need to add a single click of rebound damping. If they return to the sag point without going beyond it, then you need to reduce the rebound damping by one click.
4. Repeat the process one click at a time until the rebound takes you just beyond sag then settles back to sag. Make a note of the number of clicks from fully closed on your phone.
5. Now you can play with the damping out on a ride and always be able to return to the baseline.
PRO TIP: You will need to reset the rebound damping if you change the air pressure or progression using volume spacers.
How to set compression damping
Not all suspension forks or rear shocks have adjustable compression damping so this section may not be applicable to you.
If your suspension does have adjustable compression damping, you don’t HAVE to adjust it if you feel it might be a bit beyond you at the moment. that’s fine. Go ride your bike.
Compression damping affects how your suspension compresses.
Not enough compression damping will result in suspension that bobs around and dives through its travel while pedalling, descending and/or under braking.
Too much compression damping will prevent your suspension from absorbing impacts effectively. You’ll feel it kick back at you, also known as ‘spiking’. If the palms of your hands feel sore at the end of a descent, you may have too much compression damping on your fork.
Compression damping is again, a thing of personal preference. Some riders like an easy-moving supple suspension, other riders prefer super stable suspension that doesn’t move eagerly. Think firmly-sprung rally car versus cushy family estate car.
Generally speaking, a lot of riders don’t have enough compression damping dialled on. Their suspension bobs around and dives excessively.
Preset compression damping modes
A lot of rear shocks (and some forks) have built-in presets for compression damping. Fox forks and shocks, for example, often have a pedal platform mode with more compression damping and an open mode with less.
The pedal platform mode means lots of compression damping, resulting in a firm ride that resists moving under pedalling (bobbing) but doesn’t give up sufficient suspension travel on bumps.
Open mode means minimal compression damping, resulting in a supple, plush ride but one that can be wallowy with excessive bobbing.
Trail mode is the general all-rounder setting. Firm enough to avoid excess bobbing but still able to absorb decent hits.
RockShox and other companies have similar presets.
Low speed compression
If you have suspension with properly adjustable compression (as opposed to built-in presets) then it’s worth getting to know how it works.
Basically low-speed compression affects how the suspension compresses at low speeds and during low amplitude forces.
Dial in low speed compression until your suspension doesn’t bob about excessively under pedalling. Some bob is fine (often unavoidable really) but it’s nice to get rid of your suspension pogo-ing around robbing you of energy and control.
Don’t worry about losing small bump absorption too much; your tyres are there for soaking up the small stuff.
With low speed compression dialled in suitably you’ll also find that your fork doesn’t dive or sink through its travel during steep descents, especially those where you’re braking significantly.
High speed damping adjustments
Not a lot of suspension forks or rear shocks have adjustable high speed damping (rebound or compression). It’s reserved for high end units intended for knowledgable riders and racers.
Setting high speed damping is something of a dark art. Most riders dial off the high speed compression. They also dial in a few clicks of high speed rebound if they’re riding terrain with lots of jumps and drop-offs.
We’re not going to go into adjusting high speed damping in this guide. If you have a shock with high speed damping adjustment, your best bet is to refer to the instruction manual and/or website of the manufacturer.
How to adjust spring progression in mountain bike suspension
Believe it or not, on a lot of suspension nowadays you can have it behave in a certain way for the first part of its travel whilst at the same time have it behave in a different way for the latter stage of its travel.
In other words, you can have a supple, linear rate action for the first third (approx) of your suspension’s travel and also have a firmer, ramping up action for the latter third of your suspension travel.
This tweaking of your suspension’s spring rate is done via volume spacers.
Inserting volume spacers into your fork (eg. RockShox’s Bottomless Tokens) or rear shock only affects how your suspension feels for the last part of its travel. How the suspension behaves at the sag point or in the middle part of its travel remains unaffected.
If you’re a lighter rider, or a rider who rides relatively sedately on milder terrain, you’ll be fine with your suspension as it is. You don’t nee volume spacers. Just ride your bike.
If you’re a heavier or more aggressive rider tackling technical terrain at high speeds then you can really benefit from increasing the progressivity of your suspension.
With volume spacers installed you can run lower air pressures in your suspension and/or less low speed compression damping and have a supple freely-moving action to the early stages of your suspension’s travel whilst at the same time avoiding a fork that blows/dives through the latter stage of its travel too eagerly.
Don’t forget to burp your suspension!
This isn’t an essential thing but you may wish to do it, just because. What do we mean by “burp”? Basically air can get trapped beneath your fork’s dust wipers. It doesn’t have a huge effect but it can cause them to lose a bit of suppleness.
How to get rid of the trapped air? Get hold of a small zip tie and carefully push it between the fork stanchion and the dust wiper seals. Insert the zip tie only a centimetre or two. You may hear a small hiss of air come out.
If you do, remove zip tie slowly and get back to setting your suspension up as before. If you don’t hear any air hiss out, never mind. There wasn’t any trapped in there. Slowly remove zip tie and carry on with other setup twiddles. If fork feels a bit sticky, it’s probably in need of a quick lube mini-service.
And finally, look after your suspension!
Don’t neglect your suspension. It will degrade depressingly quickly if you do, especially in filthy conditions. This is more true for forks as it is for rear shocks (although you should still keep an eye on your rear shock).
You’ll be surprised how easy and quick it is to perform a basic clear-out and lube-up job on your fork and rear shock.
You probably won’t need any weird specific tools but you will need to get hold of some suspension fluid that is designed for your particular brand of suspension.
Looking to upgrade your suspension? Check out our guide to the best mountain bike forks and best mountain bike rear suspension, which covers both air and coil shock options. Or if it’s time for a full upgrade, our guide to the best mountain bikes has something to suit every riding style and budget.