A job certainly not easy and rarely talked about. Here are some basic tips to adjust the suspension in order to get a good trim in every condition of use. We gain in safety and driving pleasure. Before proceeding with the suspension adjustment, it is of fundamental importance to tune the operation between the front and rear suspension, in order to limit as much as possible the imbalances that the roughness of the road surface leads to the balance of the motorcycle. Choosing good shocks are crucial for your safety, so choose carefully. If this is not taken into account, there is a risk of abnormal reactions of the motorcycle in the presence of external stress, with consequent danger of loss of control of the vehicle. In addition to tuning the front suspension with the rear suspension, it is important to harmonize the functioning of the shock absorber with the relative spring, avoiding, for example, to preload the spring too little and instead braking the hydraulics too much, obtaining a suspension that sinks too much for every little roughness and then struggling to relax.
Another parameter to take into consideration is the tire pressure which must be that prescribed by the manufacturer. Adjusting the suspensions with the wrong tire pressure is totally useless.
This type of adjustment can be divided into two distinct and separate phases. The first is a static adjustment in which you adjust the bike’s trim, i.e. the height of the front and rear end in driving conditions; the second is a dynamic adjustment where you intervene on the adjusters to improve the behavior of the motorcycle, for example during a corner or when braking.more
Always remember that in order to obtain an effective functioning of the suspension according to the settings of the shock absorber, whether it is the single shock absorber or the fork, it is important that these components are 100% efficient. A check by a good suspension mechanic is necessary for an overhaul that keeps the working fluids (nitrogen and oil) in the correct state.
Static adjustment Preload adjustment (static sag without rider)
- Fully open the brake hydraulics in compression and rebound of both the fork and the single shock absorber.
- Lift the wheels completely off the ground, grasping the bike from the frame and not from the suspension components.
- When the bike is raised, measure the distance between the wheel axle and a fixed point on the frame (a screw for example). The ideal line between the wheel axle and the fixed point should be as perpendicular as possible to the road surface.
- Place the wheel on the ground and repeat the measurement shown in step 3. The difference between the two measurements is called static sag. For medium and maxi sport bikes and for road use, the static sag should be 20-30% at the front and 5-10% at the rear. For track use, the values become 15-20% at the front and 5-10% at the rear.
- Repeat the measurement of point 4 limited only to the rear with rider on board (sag rider), petrol and any passenger and luggage. In these conditions the lowering of the rear should be 20-30% for road use and 20-25% for track use. Also in this case the measurement must be made taking as reference the one determined in point 3.
- To adjust the fork hydraulics, pull the front brake lever.
- Compress and extend the fork repeatedly, loading it from the handlebar.
- Let the fork extend by removing the load but always keeping the brake lever pulled. The fork should extend completely and then compress slightly. If the fork does not sink after extension, then the compression brake is excessive. If, on the other hand, it should swing for a few moments, then there is too little rebound braking.
- To adjust the rebound brake of the monoshock absorber it is necessary to compress it abruptly and let it extend. The full rebound must be done in about 1.5 sec. Adjust the brake in compression as indicated in the owner’s manual. The dynamic regulation is much more complex than the static one because in this phase also the driving style and the driver’s impressions take over. The purely scientific and theoretical disquisitions must, therefore, give way in part to the feelings that the pilot feels when driving. It is important to make one adjustment at a time proceeding in small steps, so that you always know in which direction you are going. According to this advice, therefore, it is always advisable to try one register at a time by turning it one or at most two shots for each attempt.
To make this guide easier to use, here are several situations that may occur when the suspension is not adjusted in the best way. It will be easy to identify the case that comes closest to the behavior of your motorcycle and then follow the relevant instructions.
The bike is stiff in a straight line and tends to jump over rough terrain. The preload and compression brake are too high.
The wheels do not copy (follow) the roughness. The spring preload is too high.
Motion tends to sway in fast bends. It is necessary to increase both the preload and the compression brake.
When braking, the bike breaks down excessively in front and skidding with the rear wheel. The fork springs are poorly preloaded and the compression brake is insufficient.
The front end is unpredictable and unsafe in the center of the curve. Rebound braking is excessive or insufficient. The compression brake is excessive.
The bike tends to widen the trajectory. The spring preload of the fork springs is excessive or the spring preload of the monoshock is insufficient as well as the rebound brake of the monoshock may be excessive.
The bike tends to close the trajectory and the rear tire tends to drift. The rear end is too preloaded or there is an excessive compression brake of the shock absorber. The fork is poorly preloaded.
Summing up for a good dynamic adjustment you must take into account that:
The preload is used to adjust the height of the bike as well as to give a more or less dry operation of the suspension on roughness. Therefore, acting on this parameter modifies the behavior of the bike in bends that can go from under to oversteer depending on whether you increase the preload of the fork or monoshock. The compression and rebound brakes are used to adjust the speed at which the suspension is compressed or extended. Suspension adjustment is always a compromise between the different situations you may encounter while riding. In fact, an optimal setting for braking will not be optimal for driving on a bumpy stretch of road, just as a twisty track setup will be detrimental for fast ones.