Performance Suspension Tuning

Suspension settings can make or break the ride of your bike. The most common problems result from the wrong spring rate or air pressure. The spring is the actual energy absorbing unit, with dampening there just to control unwanted or chaotic motion. To use dampening in any other way is a crutch and impairs the function of suspension. The goal is to have as little dampening as possible - this allows for a quick response and minimizes shock stress.

Spring rate is the first thing to set up. Two things you are trying to achieve are, desired sag (negative travel) and bottoming resistance. Sag determines the height of your chassis and also the level of front versus rear. Find ing the best balance and center of gravity is an unimportant key to good handling. This balance can only be found by trying all combination of preload front and rear until, by race car terms, the chassis is neither too loose (rear skids too easily) nor too tight (front skids too easily) in turns. Rider style and conditions vary so small experiments once you have achieved a good balance and height are often necessary. This process should identify any spring rate problems:

1. Bike will not sag enough even without preload - too stiff
2. Bike sags too deep even with all available preload - too soft
3. Bike bottoms harshly with correct sag - too soft
4. Full travel is not used - no bottoming with correctsag - too stiff

Preload adjustments do not affect the spring rate for a coil shock but do affect the spring rate for an air shock. You may have to sacrifice suspension efficiency on an air shock to get the right height, unless the shock height is adjustable independent of air pressure (such as Cannondale Jekyll). With spring shocks the coil may be exchanged for another with a differrent spring rate. ACtual chassis height takes precedence over ultimate suspension performance but for optimum feel, a sag of 30% is about right. Now with the chassis balance, spring rate and hopefully the optimum feel, dampening adjustments can be experimented with.

Compression dampening is usually not adjustable for fear that a situation of too light a spring combined with high compression dampening could blow the seals. Changing the oil viscosity can make a difference although too light a weight of oil can also blow seals. Some shocks have a shim stack to which precision shims or washers can be added or subtracted to slow down or speed up compression. The lightest compression rate possible is deisred for quick response to bumps. Most shocks will already be light enough and heavier dampening should only be tried if fork dice is problematic even with the proper spring rate, or if bobbing is objectionable in certain sections and dampening is adjustable "on the fly," (remote lockouts would be an even better solution). Some new shocks have high and low velocity adjustments for compression dampening. Low speed adjustments allow for slow movements, but oil blows through a pop off valve for high speed on hard bumps. Bobbing is minimized but, the sensitivity to small bumps suffers.

Rebound rate should also be as light as possible to keep the shock from "packing" down under repeated bumps but not so light as to have the bike pitch up violently after the harshest hits. The rider may be willing to deal with a lot of pitch to get a fast action out of the suspension but that is a personal preference. Simply set the dial for the full fast response and try one click at a time until the rebound is slow enough on big hits.

Remember, until you find the best spring rate and ride heights, dampening adjustments will be a crutch and not produce the ultimate speed capability.