Bikes are becoming faster and more sophisticated by the day, and their chassis ever more complicated. Suspension systems have become a real headache not only for racers but road riders too. Here is a concise explanation of the various adjustments you are likely to meet.
Spring loading, hydraulic adjustments, compression and rebound are no longer terms confined to the specialist press. We now read and hear them every day even in the context of normal road-going bikes. It is obvious that increased engine performance and stickier tyres need better suspensions to cope, even on so-called “entry level” machines. The result is that even if you are not a serious racer, even if you never go anywhere near a race track, you are still likely to have to cope with adjustments that are more complex than ever before. All you can do is take one step at a time and always apply common sense.
Spring loading, hydraulic adjustments, compression and rebound are no longer terms confined to the specialist press. We now read and hear them every day even in the context of normal road-going bikes. It is obvious that increased engine performance and stickier tyres need better suspensions to cope, even on so-called “entry level” machines. The result is that even if you are not a serious racer, even if you never go anywhere near a race track, you are still likely to have to cope with adjustments that are more complex than ever before. All you can do is take one step at a time and always apply common sense.
When they first leave the dealers, all bikes have their suspensions adjusted to the manufacturer’s default settings. These normally give a good compromise between comfort and control under typical road-going conditions. Adjustments let you adapt the performance of your suspensions to suit your own needs and preferences. If you want adjust your suspensions, always write down what the initial settings are before you start and record every change you make. Above all, only make one adjustment at a time. These simple precautions allow you to return to the original settings if your adjustment does not have the desired effect. Making more than one adjustment at the same time combines different effects and makes it impossible for you to know exactly which adjustment does what – a perfect recipe for disaster!
PRELOAD
Spring preload is the simplest of all adjustments. You will need to adjust spring preload to adapt the bike to variations in load. If you intend to travel two up with luggage (as when touring in summer) you may need to increase preload to make the spring harder and prevent bottoming out. Spring preload is the most common adjustment as well as the simplest. That is why many touring bikes now feature a special knob to adjust preload quickly and easily.
HYDRAULIC SUSPENSION SYSTEMS
Hydraulic suspensions can be more or less sophisticated but always provide three basic types of adjustment, spring preload, compression damping, and rebound damping. On technically advanced machines, the front fork and the rear shock both offer all three adjustments. Each of these adjustments has an effect on the dynamics of the bike and on riding comfort. The adjustments themselves are normally easy to make and require only a few simple tools (typically a screwdriver and the shock adjuster wrench) plus, of course, a minimum of mechanical experience.
You need to know exactly what you are doing when you make these adjustments. The same criterion normally applies to all of them: screw in to increase effect; screw out to decrease effect. Hydraulic spring preload adjustments are particularly simple: Screw the adjuster in to increase spring preload and obtain a harder suspension, or screw it out to make the suspension softer. Unfortunately, undamped springs bounce, making control difficult. That is why the front fork and the rear shock contain oil. Forced through specially calibrated holes, this oil damps the spring action to a greater or lesser extent. In simple systems the holes are of a fixed size. In adjustable systems the size of the holes can be varied to obtain greater or lesser damping action. By adjusting compression damping you adjust the action of the suspension during compression. In practical terms, screw in the adjuster to make the suspension slower to compress.
By adjusting rebound damping you adjust the action of the suspension during rebound (the stroke that returns it to rest position). The ideal suspension set-up is always a compromise between firmness and comfort. Suspensions that are too soft tend to bottom out. Suspensions that are too hard reduce comfort and even reduce control on uneven road surfaces. Hydraulic adjustments can be made individually, but normally if you adjust preload you will also need to fine tune the damping adjustments to avoid too much bounce.
The following is a brief glossary of terms to help you follow technical talk about the difficult subject of suspension adjustments.
SPRING PRELOAD
Spring preload is the static load imparted to the spring. In simple terms, it is the force with which the spring is compressed when the bike is stationary with no load on it.
REBOUND
The rebound stroke is the suspension return stroke, i.e. the stroke that returns a compressed suspension to its rest position.
COMPRESSION
The compression stroke is the stroke that compresses or pushes in the suspension as the result of load or shock.
COMPRESSION DAMPING
Compression damping is the adjustment that allows you to control how quickly/easily the suspension can be compressed under load. Screwing the adjuster in increases compression damping, screwing it out reduces compression damping.
REBOUND DAMPING
Rebound damping is the adjustment that allows you to control how quickly/easily the suspension rebounds (returns to rest position) when load is removed. Screwing the adjuster in increases rebound damping, screwing it out reduces rebound damping.
CLICKS
Some suspension adjustment systems click as they are turned to help you identify the setting position.
RISING RATE SUSPENSIONS
These are special suspensions that use a system of levers or linkages to become harder to compress the more they are compressed.
END OF STROKE / WHEEL TRAVEL
This is the full distance through which a suspension system can move. These physical limits should never be reached.
