4 THINGS YOU NEED TO KNOW
Low-speed damping 1
When you are rolling the throttle on and off through turns or accelerating down a slip-road onto a motorway, that’s low-speed damping. Low-speed compression damping normally uses a needle to control oil flow. If the low-speed rebound damping is too strong the back of the bike is held down which may make it run wide under acceleration or judder under braking.
High-speed damping is related to the speed of the suspension, not the speed of the bike. So bumping up a kerb at 5mph is a similar high-speed action to hitting a bump mid-way through a 70mph sweeper. Too much high-speed compression makes a bike harsh over the bumps. If you are getting a pounding through the bars or kicked through the seat down an uneven back road, that’s too much high-speed compression.
Steel is the basic material, then chrom-moly steel which has silicon incorporated to give it a consistent spring rate memory. Titanium is the preserve of competition bike as it is twice as expensive but also very light. Spring-rate is the amount a spring moves when a force is applied. A linear-rate spring will compress at the same rate throughout its travel, while on a progressive-rate spring this will alter as it compresses.
Stacks of shims with different thicknesses allow the shock to deliver different damping rates through the stroke. Some set-ups, like that of a supermoto, will have crossover shims, say after every six standard shims to give three-stage damping to cope with the mix of smooth track circuit and big bumps or jumps. They allow pressure to blow off on a bump, while keeping the shock and spring further up the stroke on smooth sections.
So much more than a giant spring
Oil passes through the shim stacks