Adjusting Preload
 

Preload is adjusted at the top of the fork tubes. By using a socket or wrench, increase preload by turning clockwise, and decrease preload by turning counter clockwise. Count the number of turns in or out so both fork tubes are adjusted equally.

 

Normally there are two rings on the top of the shock, the first is a locking ring and this needs to be turned counter clockwise to loosen. Turning the bottom ring will either compress (clockwise), or allow the spring to extend (counter clockwise). A spanner wrench is the best tool for adjustment, (spray the treads with WD40 first). Make certain to count how many revolutions you turn the adjusting ring. Often, one or two revolutions will change settings drastically. Once the adjusting is done on the rear shock make certain to re-tighten the locking ring.

   

Too much sag
The spring needs to be compressed more by turning the adjuster clockwise.  

Too little sag
The spring needs to be extended by turning the adjuster counter clockwise.

With properly set static sag, you have the best chance of operating in the middle of the travel.      

Sag is a measurement of how much the suspension is sagging with the bike on a level surface, and you sitting on the bike in your riding gear. This will determine if you have the right springs, or if more or less pre-load adjustment is needed. If the springs are too soft or too hard for your body weight, the suspension will not operate properly.

            

How to Measure
            Have a helper stabilize the bike by holding the front fairing (kickstand up). Raise the rear of the bike until the shock is fully extended. Holding it in this position have the second helper (who will do all the measuring) measure from the rear axle to a point, marked with tape, on the tail of the motorcycle. Our 999R measured 470mm completely extended.

            

Wearing your riding gear, and with the helper still stabilizing the bike, mount the motorcycle. Have the second helper slowly push down on the tail approximately one inch, then let it return by itself. Have the second helper measure the same two points. Our measurement was 425mm.

            

Remaining on the motorcycle gently lift the rear a little and allow it to settle slowly. Again, have the second helper measure from the same points as before. The measurement on our 999R changed to 435mm.

   

Midpoint

The second two measurements provide a repeatable midpoint. This midpoint is more accurate for measuring. Our Ducati’s midpoint was between 425mm and 435mm (430mm). Subtracting the 430mm midpoint from the 470mm starting measurement is the rear shock’s static sag (35mm).

       

For racetrack use, static sag should be approximately 21 to 37mm, and for street riding approximately 30 to 41mm. These numbers are not absolute. You may find the bike works better with more or less static sag depending on your riding style, but you need to get a baseline measurement.

            

Measuring the static sag should be done on both the front and rear of the motorcycle, and the amount of sag should be equal at both ends. For measuring the static sag at the front, simply repeat the process, having a helper stabilize the bike from the rear, while the other measures from the front axle to a fixed point on the fork.

            

If the numbers are not in the proper range you can first make changes by adjusting the pre-load on the shock or forks. Since I am racing, and like the bike to be stiff, we cranked the preload collars on the rear shock to end up with a static sag measurement of 26mm.

            

If you cannot get the static sag to be in the range from adjusting the preload, you may need to change the spring itself to one with a different spring rate. Seeking professional help at this juncture is recommended due to the fact that this normally requires changes to the shock’s (or forks’) internal damping. 2WT
           
            David Podolsky is the founder of Chicken Hawk Racing, and multi-time WERA singles and twins national champion.