Meet of the week

What com­pres­sion, re­bound and spring preload mean – and what needs tweak­ing

Motorcycle News (UK) - - Riding -

Get your­self down to the Ox & Plough

1 Front re­bound ad­just­ment

The re­bound ad­juster con­trols the speed at which the forks re­turn to the open or ex­tended po­si­tion. This ad­juster is lo­cated usu­ally on ei­ther end of the forks – on older bikes it is com­monly at the top. Turned all the way in, it will slow down the fork’s re­turn; ad­justed to the low damp­ing set­ting, the forks spring back very quickly. Add or re­move damp­ing a click or half-a-turn at a time, then fine-tune in smaller in­cre­ments.

2 Fork preload ad­just­ment

Fork preload is the amount that the front spring is com­pressed when in its nor­mal rest­ing state. In­creas­ing the preload will re­duce the amount that the bike sags on its springs and will give the in­pres­sion of the forks feel­ing harder. Like­wise, wind­ing the preload out will make the sus­pen­sion sit lower in its stroke and the forks ap­pear to feel softer. The ad­juster is usu­ally sit­u­ated on the top of the fork.

3 Front com­pres­sion ad­just­ment

The speed at which the fork com­presses is man­aged by the com­pres­sion damp­ing. This ad­juster is of­ten found at the bot­tom of the fork leg, but check in your man­ual as some bikes have it at the top of the fork leg. With the ad­just­ment fully turned up, the forks will feel hard to com­press and at the lower set­tings the re­sis­tance is re­moved and the forks dive more freely.

4 Fork pro­tru­sion

The fork’s pro­tru­sion through the top yoke is some­thing a lot of sports­bikes have pro­vi­sion for and al­lows you to change the ride-height of the front end by slid­ing the forks through the top yoke. Usu­ally done a few mil­lime­tres at a time, and mea­sured with a ruler or dig­i­tal vernier from the top of the yoke to the top of the fork leg ex­clud­ing the fork cap.

5 Rear com­pres­sion ad­just­ment

The rear shock shares the same ad­just­ment func­tions as the forks. The ad­juster for com­pres­sion damp­ing is usu­ally lo­cated at the top of the shock. Changes can be made ei­ther with a screw­driver/ Allen key or some­times a knob. More damp­ing will slow down the shock’s abil­ity to com­press quickly, while less will have the op­po­site ef­fect.

6 Rear re­bound ad­just­ment

Usu­ally found right at the bot­tom of the shock (check your owner’s man­ual to be sure of its lo­ca­tion). Quite of­ten it is nec­es­sary to get down on the floor to gain ac­cess to it. The ad­juster con­trols the re­turn speed of the shock: with zero damp­ing, the ride will be very bouncy and feel un­con­trolled, too much and it will feel hard and choppy.

7 Rear preload ad­just­ment

The rear shock preload ad­just­ment will usu­ally re­quire the use of a C-span­ner. Make sure you have good ac­cess, loosen the top lock­ing ring and spin it up the shock so you can get good ac­cess to the re­main­ing ring. Ad­just­ment is done by turn­ing the ring clock­wise to in­crease the preload strength, and counter to re­duce the ef­fect.

8 Mea­sur­ing your ad­just­ment

When you’re ad­just­ing the rear preload set­tings you can ei­ther count the num­ber of turns you make on the lock rings or mea­sure the amount of threads ex­posed above it. If you mea­sure the threads you can use ei­ther a ruler or tape mea­sure to do this. Make sure that you take your mea­sure­ments with the lock­ing or top ring in place, both be­fore and af­ter ad­just­ment.

9 Ba­sic set-up as­sess­ment

You can as­sess what your changes have done by press­ing down on the front or back of the bike. You can get a feel for the amount of ef­fort needed to push down the bike (com­pres­sion damp­ing ef­fect) and the speed at which it re­turns (re­bound damp­ing ef­fect). The same thing can be done by push­ing the forks down with the han­dle­bars. This will give you a feel for any changes and the range of ad­just­ment.

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