Motorcycle suspension setup: getting acquainted with a black art
Suspension Setup: The Basics
Whether you’re a road cyclist or a racer, the correct suspension setup is the key to a fast, smooth ride and consistent lap times. To get the best out of your bike, you need to set it up for the conditions you’ll be riding in. It’s considerably easier to set up the bike for the track, as you know what the conditions will be for the next hour, and can therefore dial in the optimal settings for that particular situation.
The extent to which you change your suspension settings will depend on whether your bike will also have to cope with road riding. Unlike roads, tracks are generally smooth and grippy. So if you’re only going to be using the bike on the track, you have the luxury of installing stiffer springs and modifying the internals of the fork and shock. If you drive both on the road and on the track, you’ll probably want to maintain a certain level of comfort and focus only on optimizing the current equipment.
With incorrect suspension settings, tire wear increases and handling is affected, which in turn can lead to driver fatigue. Lap times can be dramatically slower and in extreme cases safety can be compromised. Hopefully the following guide will help you fine tune your suspension for a faster and safer ride both on and off the track.
First, you’ll need to check fork and shock sag – this is the amount the forks and rear shock settle under load. To measure, do the following: push the forks down a few times to seat them, then mark the strut with a marker pen or attach a cable tie where the dust seal is located. Next, ask for help to raise the bars so that the front wheel is just off the ground and measure the distance the forks have lowered. This is the static buckling (or no-load buckling). This can be changed by adjusting the spring preload (more preload = less sag). Repeat the same process for the rear, this time measuring the distance from the hub of the wheel to a fixed point on the tail. You are now ready to start setting up your suspension. The key is to take it slowly and take notes as you go. For road riding, start with the wet track setting and work up from there.
Basic configuration: Check the following
Forks sag 18-22mm for dry track, 23-27mm for wet.
8-10mm cushioning for dry track, 10-14mm for rain.
Check chain alignment. If not correct, the bike will crab and increase sprocket wear.
Proper tire balance and pressure, starting with 30 psi in the front and 32 psi in the rear (both dry and wet).
Steering Head Bearings and Torque Specs – If they are too loose, there will be head shake at high speeds.
front alignment. Check wheel alignment with triple clamps. If it is misaligned, the fork geometry will be incorrect and steering will be affected.
Crash damage, check frame geometry is correct.
Stock Suspension Adjustment Limitations
Manufacturers plan to design a bike that will work moderately well for a wide range of riders and uses. To achieve this as cheaply as possible, they use valves with very small venturis. These are then combined with a very basic shim stack that creates a damping curve for the given suspension component. At lower speeds, this design may work moderately well, but at higher speeds, when the suspension must react more quickly, the suspension will not flow enough oil and will experience hydraulic lockup. With hydraulic lockout, the fork and/or shock cannot damp properly and handling suffers. The solution is to re-valve the active components to obtain a proper damping curve. No matter what components you have (Ohlins, Fox, Kayaba, Showa), combining them with their intended use and weight will greatly improve your action. Also, if you can achieve the damping curve that is needed, it doesn’t matter what brand of component you have. Often with original components, when you turn the adjusters in or out, you won’t notice a difference. In part, this is due to the fact that the manufacturer placed the damping curve in an area outside of its ideal range. Also, because the valves have such small venturis, changing the adjuster makes very little difference. After re-valving, the adjusters will come into play, and when you make an adjustment you may notice that it affects the way the fork or shock works.
Another problem with the stock suspension is the springs that are used. They are often progressive, increasing the spring rate with greater compression distance. This means the valve is correct for only part of the spring travel, everything else is compromised. If the factory installs a direct rate spring, it is rarely the correct rate for the weight of the rider with gear. The solution is to install a straight spring that matches the valve for the combined weight of the bike, rider, and gear for the intended type of riding.
Remember!
o Always make small adjustments, more is not always better.
o Always keep notes of what you have done.
o Suspension tuning is an art: be patient