How to Setup MTB Suspension

One of the most common questions we get asked from clients is how to setup MTB Suspension. Often a client will remark upon how much more confident and stable their bike feels with a service and some relatively minor adjustments.

But where do you start? It’s worth noting that there is no such thing as a perfect suspension setup for any one bike or rider. Trail conditions, riding style and where you are riding will undoubtedly change, so should your setup if you want to get the best out of your steed. Even with this in mind however finding a good base to work from is half of the battle. Just remember that whilst there is no such thing as a perfect setup for every inch of trail (it’s all about compromise), you can still have a very bad setup.

Knowing what each dial does, why you would adjust it, a smattering of experimentation and interpreting the way the bike feels as a result are all parts of the process. There are commercially available suspension tuning sensors nowadays like the Quarq Shockwiz which make getting a good setup a piece of cake, but assuming you don’t have one….

Here is our step by step guide to setting up your bike’s suspension, an explanation of what each adjustment does and what the symptoms of poor suspension set up are. This will give you a good base to work from so you can make minor tweaks.

Make sure that you set your forks or shock up using these 3 steps in this order:

Step 1 – Setting Sag

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Manufacturer’s pressure guide.

Sag is how much your suspension compresses when you are sat on the bike whilst stationary with just the weight of you and your kit. The more sag you have, the softer the ride will feel.

Sag will give your suspension some ability to match the undulations of the trail by extending and pushing the wheel into dips. Sag will help keep the wheel in contact with the ground and will improve traction.

How will the bike feel with not enough sag?

  • Not enough sag will result in a harsh and very nervous feeling bike.
  • Like you haven’t got enough traction.

How will the bike feel with too much sag?

  • The bike will dive through it’s travel too quickly and may “bottom out” (run out of travel) again the bike will feel harsh but in extreme cases it could result in damage to the bike and/or suspension components.
  • In the case of the forks too much sag can mean that the front end of the bike is constantly running low, on the rough stuff you will feel as if you are going over the bars and the imbalanced weight distribution of you on the bike could mean that the trail feels more bumpy than it actually is.

Manufacturers will usually recommend a sag setting and express it as a percentage of total travel, your forks/shock may even have handy little markings (such as with Rockshox). As a very rough/general guide you will be looking at the following starting points:

  • XC/Race – 80 to 100mm travel – 15 to 20% sag.

    how to setup mtb suspension, mtb suspension servicing, mtb suspension repair

    Manufacturer’s sag guide

  • Trail/All Mountain – 100 to 160mm travel – 20 to 30% sag.
  • Freeride/Downhill – 160 to 200mm travel – 25 to 35% sag.

The above is not the be all and end all, we have seen some very fast DH riders run 45% sag, but it’s a good place to start.

Also note that when setting the sag on the rear shock, 10mm of shock compression or stroke length doesn’t necessarily translate into 10mm of travel on the back wheel. This is down to the design of your swing arm, pivots etc. (further explanation of stroke length below).

Steps to setting Sag:

    1. When setting the sag on your bike make sure you are carrying and wearing everything you would on a normal ride such as water, tools, spares, armour, helmet etc. to ensure that you get an accurate reading.
    1. Confirm the stroke length of your rear shock from the manufacturers website. If you can’t find this measure the shock from eye to eye, let out all of the air and measure again. Subtract the second figure from the first and you will have your stroke length.
    1. Set the O ring on the forks/shock so it is up against the base of the shaft/stanchions.
    1. Climb onboard the bike carefully so as to not compress the shock/forks excessively. Prop yourself up against a wall and allow your bike to take your full weight.
    1. Get off the bike and measure how far the O ring has moved on the fork/shock, this is your current sag setting. Add or remove pressure accordingly until the O ring has moved the desired distance and you fall within the 15-35% of sag as set out above.
  1. If you have a coil shock/fork you will need to substitue your coil spring(s) to change the sag. You can increase or decrease preload which will stiffen up the fork or shock but it’s a common misconception that you can use preload to adjust sag, you can’t, you need a different weight of spring.

If you don’t have an O ring you can use a zip tie instead. Make sure the bike is clean first and remove the zip ties before going for a ride to avoid damage to suspension components.

Step 2 – Setting Rebound Adjustment

Rebound Damping controls the rate at which the forks or shock will return to a relaxed state following an impact.

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Rebound adjuster

Downhill Bikes with lots of travel will usually have much more rebound damping (resulting in a slower rate of return) than an 80mm XC bike.

Usually we see setups with little or no Rebound Damping rather than too much.

How will the bike feel with not enough Rebound Damping?

  • As the suspension returns to full length more quickly the wheels will drop into more bumps and gaps rather than floating over them, resulting in a rough ride.
  • The bike will feel wild and skittish generally, often bucking you about as the fast return kicks you up the bum, especially on rough terrain or on the jumps.
  • During hard cornering there will be a noticeable reduction in traction.

How will the bike feel with too much Rebound Damping?

    • The bike will feel harsh, unsettled and squirmy as it may bottom out due to the fact that the suspension cannot extend quickly enough between impacts. In respect of the forks it may feel like the front wheel is wandering. Sometimes this can be misinterpreted as too much Compression Damping or running the forks/shock too stiff. Riders will then reduce compression damping or shock pressure which only makes things worse.
  • The bike feels as if it is squatting down during high speed cornering especially in berms.

Steps to setting Rebound:

Forks

  1. Standing next to the bike press the forks down sharply and release them taking all weight off the bars.
  2. If the front wheel is lifted clear off the ground by the forks extending, add more rebound damping until the front wheel stays completely on the ground.
  3. If the forks take a noticeable about of time to return to full length reduce the rebound damping to the point that the wheel just stays on the ground.
  4. Ride the bike – then move the adjuster 1-2 clicks either way and decide which setting feels the most stable.

Rear Shock

  1. Climb onboard the bike, in a standing position whilst rolling forward quickly drop into a seated position compressing the rear shock.
  2. The bike should not bob down and up more than once or throw you back up so quickly so that it feels as if the bike is throwing you up out of the saddle. If it does add more rebound damping and repeat.
  3. If the rear of the bike doesn’t feel as if it pushed you back up at all remove some rebound damping until it feels that the bike bobs down and then up once in a controlled manner.
  4. Ride the bike – then move the adjuster 1-2 clicks either way and decide which setting feels the most stable.

Step 3 – Setting Compression Damping

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Compression damping adjustment.

Compression damping controls the rate at which the suspension will progress through it’s travel during an impact. There are two types of compression damping – high speed compression damping and low speed compression damping. Not all forks/shocks have both high and low speed adjustment however. If you just have 1 adjuster this will be low speed.

Think low speed compression for controlling fork/shock dive under braking before entering a corner and for a pedal platform (so the bike doesn’t bob around too much). High speed compression damping for bigger hits such as a fast impact from a big drop.

How will the bike feel with not enough Compression Damping?

Your forks or shock will plummet through it’s travel too quickly out on the trail, often resulting in the fork bottoming out. The bike will also bob around too much when trying to pedal.

How will the bike feel with too much Compression Damping?

In both cases (low and high speed) too much compression damping will result in a harsh ride, little or no bump sensitivity and a nervous feeling bike.

Steps to setting Compression Damping (fork and shock):

  1. Start with the adjuster set in the middle – this won’t work properly if you haven’t set your sag first.
  2. Monitor how much travel your fork/shock uses on your usual trails, if the o ring on your stanchions/shock body indicates that you are using a lot of travel, all the time, even when the trails aren’t that rough add a bit more low speed compression damping.
  3. If you find that your bike has little small bump sensitivity try reducing the low speed compression.
  4. If you are bottoming out your fork/shock on every jump add some high speed compression damping (if you have a high speed adjuster), if you aren’t using all of the available travel after a big impact, reduce it.
  5. Points 3 and 4 assume you have set your sag correctly as described above.
  6. For those with a Fox CTD fork or rear shock, this is your compression damping.

Troubleshooting

Q. My compression/rebound damper doesn’t seem to make any difference to how the fork or shock feels, why is this?

A. Some forks/shocks have a more effective range of adjusters than others, for example some don’t really have any impact until the last few clicks of adjustment at which point the changes become apparent. However if the rebound and compression adjusters make no difference whatsoever it could be that your forks have the incorrect oil levels in them, in the case of Fox’s FIT or Rockshox’s charger damper the bladder may be split. For rear shocks no damping whatsoever indicates that the damper has lost it’s charge, whether it be nitrogen or air. In both cases a service and/or repair will be required to rectify.

Q. My forks or shock feel very nervous if I run any compression damping at all, why is this?

A. Chances are you are not running enough sag, refer to step 1. One of the most common issues we see is that clients run too little sag and then try to compensate by running no compression damping.

Q. My forks are losing travel, why is this?

A. If your shock or forks are loosing travel it can be either:

  1. The unit has become “stuck down” this is caused by an internal air leak – the pressure is ending up on the wrong side of the piston and is compressing the fork or shock. Usually the owner tries to correct this by simply adding more air which will appear to cure the problem initially but after riding the bike for a short distance the problem re-appears. Increasing the pressure in this situation can be dangerous, especially for an inexperienced DIY mechanic as the relevant component can go off like a gun when they begin to disassemble their fork/shock. Usually this problem can be corrected with a service, in rare cases a replacement component or two may be required (warped air cans spring to mind).
  2. You may just be losing pressure from your forks or shock. If the fork/shock returns to it’s original state fine but you find them too soft after you have added more air then you may just need a service. In the case of rear shocks usually just an air can service will rectify the issue provided the unit hasn’t been neglected to the point that there is damage to the anodising on the shock body..

Summary

Setting up MTB suspension isn’t magic, you can do it yourself if you follow the guide above, but if you are anywhere near the Preston area and want somebody to talk you through everything please feel free to pop in for a brew and a chat 🙂