4 THINGS YOU NEED TO KNOW

Motorcycle News (UK) - - Garage -

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

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.

Springs 2

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.

Shims 3

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

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