Mountain Bike Suspension Setup

SUSPENSION SETUP TIPS

 

 

SAG: This is the amount that the suspension compresses when you sit on your bike in full riding gear – used so that your tyres can follow the terrain and don’t leave the ground every time you hit a trail feature.

The amount of rear end sag you run depends on frame your design (different linkages and frame designs mean that rear wheel movement is not always equal to stroke length) and rider preference.  Frame and shock manufacturers recommendations vary, but as a rule: 25-30% of total shock stroke length should be sagged for freeride and downhill and 15-20% for cross cross country and all mountain, somewhere in-between the two for enduro depending on your riding style; the same values also apply for fork sag.

You should be setting your sag whilst fully clothed in your normal riding gear and hydration pack (filled with water and your usual spares etc).  Set your sag ring at the bottom of the stanchion so that it rests against the dust seal on your fork or shock.  You can also use a cable tie quite loosely attached to your stanchion in such a way that it will remain in place after the fork is compressed.  Get on your bike as lightly as you can and assume the attack position whilst leaning carefully on something to steady yourself.  Get off the bike carefully to avoid adding any jolting input that will move the sag ring and measure how far up the stanchion that sag ring has moved.  Adjust air pressure accordingly to achieve the percentages mentioned above.

If you have any pro pedal or Climb Trail Descend type features on your shock or fork these should be turned off when setting the sag.  The shock should be completely open.

 

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A: Eye 2 eye length

B: Stroke length

 

PRELOAD: This is used for fine tuning sag on forks and shocks with coil springs

Spring rate (defined as the load in pounds applied to a spring divided by the deflection of the spring in inches, so a 400lb spring requires 400lbs to compress it 1 inch & is easier to compress, or ’softer’, than a 600lb spring) and spring preload (screwing a cap down to force the spring through part of it’s travel without any input, does not affect the rate of the spring) should be chosen to give you the desired sag.

Air springs do not have a preload adjustment because sag can be easily fine-tuned via your shock pump using air pressure. The sag of an air shock with an added air reservoir will be affected by the PSI in both chambers, so altering reservoir chamber PSI after setting sag will affect sag and can be compensated for by slightly reducing the pressure in the main-chamber. Changing the pressure in the piggyback of your shock can have other affects on shock performance so seek advice if you’re not sure what you’re doing.

DAMPING & DAMPERS

The purpose of a damper is to control the compression and rebound of the spring in your shock or fork.  This is achieved by hydraulic resistance.  Your damper is a piston that is forced through an oil bath as the fork is compressing or extending.  The typical adjustment that you can make on your fork or shock opens or closes a series of holes in the compression or rebound circuit so that the piston faces more or less resistance, speeding up or slowing down the reaction to input.  There are other methods to achieve a change in the speed that the piston can move however this is the most common way on user adjustable systems.

LOW SPEED COMPRESSION DAMPING: This reduces the effects of rider based inputs and low speed moments.

The speed referred to in the phrase low speed compression is the suspension shaft speed, not the speed of the bike.  Low speed compression moments include things like pedalling forces, body movement to prepare for jumps, berms etc and landing a properly executed jump onto a nice transition.  Low speed compression should be used to dial in pedalling stability.

You should set your low speed compression to the minimum you are comfortable with to deal with your body inputs so that your fork and shock can stay higher in their travel and be ready for bigger hits.

HIGH SPEED COMPRESSION: This resists compression after high speed hits to prevent harsh bottom out.

Generally we recommend that you start with the manufacturers recommended settings for HSC.  You won’t be able to recreate the high speed moments that this setting deals with when you’re rolling around the car park.  You need to do a few test runs, feel the fork or shock and watch for bottom out by looking at the sag rings.  You’re looking for maximum travel on the biggest hits you encounter without bottoming the shock out.  You should be as near to bottom out as possible without hitting it.

RESERVOIR PRESSURE & VOLUME ADJUSTMENTS:

Changing the air pressure has the dual effect of altering the shocks preload and how progressive it is at the same time.  It will also change any pedal platform (aka ‘Propedal’) threshold too. This combined effect occurs because air has a progressive spring rate, i.e the more you compress it the harder it is to compress it further. Increasing the air pressure in a reservoir will make each inch of compression harder than it was before, therefore altering the progressiveness of the shock.

Air volume can be adjusted mechanically on shock reservoirs by skilled technicians and in many cases by the user in newer forks and shocks that offer simplified volume spacing arrangements. This can also be achieved by altering oil level in forks with open-bath damping.  These adjustments should not be undertaken if you are not comfortable with what you are doing.

REBOUND: Rebound force, unlike compression forces, are governed by one thing – spring rebound force.

Rebound damping should generally be set up to give the fastest possible rebound speed without allowing the wheel to kick out and give harsh top out.  You do not want the shock to extend too fast and top out.  You want the shock or fork to return as quickly as possible to its starting position so that it is ready to take further hits without it returning so fast that it bucks you.  This  will help to keep your tyres on the ground and keep you higher up in the softer part of your travel so you have better bump absorption when things get fast and choppy with continuous hits.

LOW SPEED REBOUND:  This is the most common damper adjustment found on shocks and forks.  It allows riders to keep the fork and shock glued to the floor.  A lot of low speed rebound damping will make the shock or fork return much more slowly from an impact whereas a very small amount will see the shock returning too quickly.  Too much and the bike will be hard to get off the floor, too little and the rear wheel will not stick to the floor which will negatively effect traction.

HIGH SPEED REBOUND:  This is there to ensure that your fork or shock returns to a position where it can provide more travel again quickly after big hits.  If you don’t have enough high speed rebound then you can find your fork or shock packing down, where it takes a big hit and can’t recover quickly enough to provide more travel for the next hit.  This is particularly important when you’re careering down a rocky descent and you need to retain control and be able to rely on your suspension to be there to soak up the big stuff. This is most often a non user adjustable feature on a lot of suspension but it can be adjusted by us as part of a tuning process. Get in touch if you feel that you need this.