Motocross Suspension Tuning Guide

CLICK SUSPENSION TUNING GUIDE

Rear Suspension Sag Chart: 

Spring Rates:

The spring rate and preload will set the ride height of the vehicle and determines how much of the total travel will be available for compression and how much will be available for droop travel.

Spring Preload is the amount of tension that is applied to the spring from its full extended (before installation) length. This adjustment is very important for proper suspension action. Too little preload and the suspension will sag too much; steering control and handling will deteriorate. Too much preload will have a negative effect on the steering and handling of the bike and will make the ride harsh.

Race Sag / Ride Height is the amount the vehicle settles with the rider on the bike in a normal seated position. Rear suspension is approximately 30% – 33%, the front is around 25% – 30% of the total suspension travel. This is why a 300 lb rider would require a stiffer rate spring and more preload to maintain the same ride height as a 150 lb rider.

Static Sag / Bike Sag /Free Sag refers to the amount the vehicle settles with no rider. This settling is about 6% – 10% of the total suspension travel. Too little bike sag can make the bike handle poorly and the ride harsh. Too much sag and you have less control over the bike, and you will lose travel of the suspension.

Damping:

Compression damping controls the shock or fork when it is being compressed.

Rebound damping controls the shock or fork when it is extending back to starting point in travel/stroke.

TUNING FOR TRACK CONDITIONS

Hard Pack / Square Edge Bump Conditions:

Adjust compression damping as soft as possible, to handle square edges while still having some control with bottoming.

Loamy Conditions:

Adjust damping a little firmer for loamy terrain, jump faces and bottoming.

Sandy Conditions:

Adjust damping towards the firmer side increase your fork compression and increase your shocks rebound. In general, two (2) clicks each. You want the bike to ride on top of the terrain, allowing the forks to ride up a little higher.

Rocks / Roots Conditions:

Adjust compression more towards the soft side of your baseline settings; this helps to absorb the small sharp hits. You can also speed up rebound both front and rear; this adjustment helps wheels react quickly from rock to rock. Compression on the softer side will also produce a very soft plush feel and help reduce arm pump/fatigue. This type of setting is good for woods or trail riding; however it will not be firm enough for fast MX track conditions; the bike will have a wallowy feeling “bouncy”, and will have bottom out issues in whoops and jumps.

Not Using Full Travel, Feels Harsh, Poor Traction While Making Turns:

Causes springs or air pressure too high in rate or PSI or compression damping to high (firm) CLICK SOLUTIONS Reduce compression damping; softer coil springs and or air pressure.

Bottoms, Soft Throughout Travel:

Causes spring rate or air pressure too low or too little compression damping CLICK SOLUTIONS Increase compression damping; stiffer Coils Springs or more air pressure.

Excessive Sag, Feels Soft Initially:

Causes Initial preload too low CLICK SOLUTIONS Increase spring preload or add more air pressure.

Harsh Over Small Bumps But Uses Full Travel:

Causes Initial spring rate or preload too high, too much compression damping CLICK SOLUTIONS Install softer springs, reduce air pressure and or reduce compression damping.

Takes First Bump In A Series Well But Harsh Over Following Bumps, Poor Traction In Washboard Corners:

Causes too much rebound damping CLICK SOLUTIONS Reduce rebound damping.

Too Much Compression:

The ride will be harsh, but not as bad as too much rebound. As shock shaft or fork movement speed increases so does harshness. Rear end and the fork will want to deflect when hitting medium to large bumps (shock resist movement even on medium size bumps) CLICK SOLUTIONS decrease compression until harshness is gone.

TIP:  To learn what clicker adjustments can do for your ride, experiment with the compression adjustments and rebound adjustments. We suggest you start with compression damping. Turn the compression adjuster to full firm, ride your bike for a while, and then turn the adjuster to full soft. This adjustment will give you an idea what compression damping can do. Likewise, do the same with your rebound adjusters; feel what fast rebound is like, feel what slow rebound is like

Wheel chatters over small bumps during braking or downhills:

Causes too much preload, causing the suspension to top out and possibly too much compression damping CLICK SOLUTIONS Reduce preload, decrease compression damping and also experiment with rebound damping reduction.

Front-end springs back too quickly after bumps, poor traction in bumpy corners:

Causes not enough rebound damping CLICK SOLUTIONS Increase rebound damping.

Not using full travel, feels harsh, poor cornering and braking traction:

Causes:  An overly stiff spring rate or too much compression damping; possibly too much preload.

Rear shock lack of compression:

The rear suspension will feel too active (wallow excessively). On jump landings, the shock bottoms too easily. CLICK solutions increase the compression “gradually until the balance/feel is optimized”. You will notice better control, and the wallow symptoms will go away.

Glossary of terms:

Coil spring:

Consists of a metal wire formed into a coil which can store energy when compressed, and releases energy as the load is relieved.

Air spring:

Air compressed in a closed chamber which can store energy when compressed, and releases energy as the load is relieved.

Compression damping:

The compression damping circuit absorbs the energy of compression forces in the oil shock damper unit.

Damper:

A fluid chamber with a means of regulating the fluid flow, to govern the speed of the moving damper piston during compression or rebound strokes.

Damper speed:

The relative speed in which the moving end of a damper compresses or rebounds.

Damping:

The process of absorbing the energy of impacts transmitted through the fork or rear shock on the compression stroke, and the process of absorbing the energy of the spring on the rebound stroke.

Damping Circuits:

There is both a low and high-speed circuit for the compression and rebound strokes.

HSC:

High-Speed Compression damping is the damping circuit in the shock absorber or suspension fork that is tuned to provide suspension travel control at high speed over square-edged bumps. Too low of HSC damping will cause excessive bottoming out in rough terrain. Too high of HSC damping will minimize suspension travel in rough terrain and cause loss of traction and tire deflection…kick up.

LSC:

Low-Speed Compression damping is the damping circuit in the shock absorber or suspension fork that is tuned to provide suspension travel control at low damper speed conditions. Too little of LSC damping will cause the excessive travel use, brake dive and wallowing on small bump terrain. Too much of LSC damping will cause loss of traction on small bump terrain.

Suspension packing:

A term used to describe the ride characteristics of a rear shock or fork that has too slow of a rebound setting. A rear shock or fork that has too much rebound setting will stay compressed after hitting one bump and cannot rebound quickly enough to reset for the consecutive bumps. The solution is to adjust the rebound to a faster setting.

Preload:

Preload is applied to the fork and shock springs in order to bring the bike to the proper SAG dimension. Adjusting preload to the proper SAG dimension ensures traction as wheel load gets light and drops into bumpy holed sections of terrain.

SAG:

The most common way to measure motorcycle rear sag is with a sag setting tool. I highly recommend the sag setting tool sold by Motion Pro.

Rider Sag or ride height is how much the fork or shock compresses with rider on the bike  (i.e., rider sitting or standing in normal riding position). Sag allows the wheel to follow terrain better. When you encounter a ‘dip’ or ‘depression’ on the trail, the sag will allow the wheel to track down into the dip. FREE SAG or BIKE SAG refers to the amount the vehicle settles with no rider on bike.

Generally (rule of thumb)  is about 35% of the total available rear wheel travel. For example, a motorcycle with 300 mm of total rear wheel travel will have about 105mm of sag with rider on bike.

For some unknown reason, many tuners don’t talk much about or measure fork sag very often.  But my rule of thumb here is about 25% sag number on forks.  The number is different than the rear because rider weight is more bias to the rear of the motorcycle.

The stroke of a shock is a ratio of the total rear suspension travel. For a rear wheel travel of 11.8”  or 299.72mm  of wheel travel a motorcycle rear suspension linkage with an average leverage ratio of 2.36, the shock stroke is 5” (127mm). To sag the rear travel 35% you would have to measure 35% of the shock stroke. In our example, 35% of the shock stroke is 1.75” (44.45mm).

Bicycle: You can measure the o-ring around the shock shaft on a bicycle air shock. Measure the distance between the shock body and the o-ring. For coil shocks, sag can be measured by using the shock eye-to-eye length and deducting the sag from the eye-to-eye length. Also, coil shocks have a rubber bumper, you can use this bumper as explained above with the o-ring on air shocks, if the rubber bumper is tight enough on the shaft.

Compression Damping: Compression damping controls the speed the fork or shock will go through its travel (or compresses). Compression is controlled by forcing oil through an orifice (small hole) and/or an elastic element covering an orifice that can be either flexible damping shims or a spring loaded shim. The resistance of the oil to go through the aforementioned orifices is what provides damping.

Low-Speed Compression controls the riders input on the suspension at ‘slow’ shaft speeds. Adding more LSC to a fork will help reduce brake dive or help keep the front end up in corners, and can also reduce suspension movement resulting from mass shifting due to pedaling (i.e. ‘bob’). The more LSC that is added, the slower the suspension will react to bumps. This can result in a ‘rougher’ ride and traction can be compromised. On the other hand, if too little is used, forks tend to have “brake diving” (i.e. the fork will sink too much into its travel when the brakes are applied) and the bike can feel nervous.

High-Speed Compression controls the terrain input on the suspension at ‘fast’ shaft speeds. This typically means the force needed to move the shock or fork through its travel from the terrain during bigger bump or hits. Adding more HSC can provide more ‘bottom-out’ resistance. Adding too much HSC for your given terrain may result in not using all the available travel.

Rebound Damping: Rebound damping controls the speed the fork or shock extends (i.e., returns back to full travel after compression).

When the rebound is set too slow, the fork or shock will not extend fast enough in time for the next bump in terrain. The suspension may feel ‘packed-down’ or ‘wallowing’ in terrain with repeated hits like in rocks.

When the rebound is set too fast, it will extend the fork or shock too fast. Your control could be compromised and you could be bucked off the bike or may feel ‘harsh’. Rebound is often set a bit slower for terrain with more big bumps resulting in drops and jumps. Rebound is often set a bit faster in faster terrain with smaller bumps occurring more often.

A rough guideline in setting rebound is to set slow enough that you can almost feel the fork or shock’s extension slow. Then try moving it faster or slower to suit your conditions.

Valve Shim:

A thin, spring steel flat washer used to exert resistance on the oil flow through a piston. A series of valve shims (valve stack or valving) with varying outer diameters and thicknesses are arranged in sequence to provide a particular damping effect.

Spring Rate:

Spring rate can be described  in pounds “LBS.” , kilograms “KG” or Newton Meter “NM”.  For further information on how spring rates are tested, please click here.  Too much detail for me to write out here. Also, you can find spring rate calculators online to give you a rough idea what your spring rate is if you do not know. Spring rate Calculator link

Stiction = Friction:

Is the combination of the words static and friction. This word is used to describe the tension exerted on the moving damper parts by the stationary parts like the bushings, seals, and wipers. Low stiction is more desirable because it has less of a negative effect on the damping.

Unsprung weight vs Sprung weight

The difference betweens sprung and unsprung

To understand the difference, imagine a  motorcycle moving forward until the front wheel hits a bump large enough to move that wheel upward towards the frames down tube. But as the wheel moves up, the motorcycle frame might not move much or at all, because it’s isolated from the upward-moving wheel by fork springs; the springs can compress to allow the frame of the motorcycle to stay where it is as the wheel moves up and down underneath it. That’s the difference: the frame of the motorcycle and everything attached solidly to it is sprung, meaning that it’s isolated from the wheels by compressible springs; the tires, wheels, and anything attached directly to them are unsprung, meaning that the springs don’t keep them from having to move when the motorcycle comes to a rise or fall in the track.

Almost all of the motorcycle is sprung weight, because almost every part of it is attached solidly to the frame. Besides the frame itself that includes all other structural or sub-frame components, the engine and transmission and of course the rider.

What about unsprung weight? The following are unsprung:

  • Tires
  • Wheels
  • Wheel bearings and hubs (the parts the wheels rotate on)
  • Brake assemblies
  • Swing arm and lower fork inner tube “sliders”.

Semi-sprung parts

Parts like this that have to move when the wheel does, but not as far, are said to be partly sprung, semi-sprung, or hybrid weight. Typical semi-sprung parts include:

  • The springs themselves
  • Shock absorbers and forks

Why does any of this matter? If a large part of a motorcycles mass is unsprung, it’s more difficult to keep the tires planted firmly on the road as it rides over bumps because the springs have to apply more force to move them. Having a high ratio of sprung to unsprung weight is therefore always desirable, and is particularly important for vehicles that are intended to handle well at high speeds. Racing teams thus reduce unsprung weight by, for example, using lightweight wheel sets, and race team engineers try to design suspension components with as little unsprung weight as possible.

Note that unsprung weight or mass is sometimes confused with rotating mass because some parts (tires, wheels, most brake discs) fall into both categories and because racers want to reduce them both. But they’re not the same thing. Rotating mass is what it sounds like, anything that has to rotate when the motorcycle goes forward. Lower unsprung weight improves handling and sometimes traction, while lowering rotating weight improves acceleration.

I hope this has helped you gain some suspension knowledge!

Neezer and family at Click Suspension

Copyright © 2018 Click Suspension Labs all rights reserved. Click Suspension Labs,Click Suspension and Liquid A kit are trademarks of Click Suspension Labs.