Adjustments+ +Forks
2
6 April 2004 FRICTION ZONE Suspension Adjustments Part 4—Forks by Dave Moss Editor’s note—This month’s article is aimed at riders who frequently work on their own motorcycles. If you have any doubts about your ability to perform the proce- dures described here, please take your motorcycle to a qualified mechanic. T HE RE AR E THRE E SET TI NGS that can be adjusted on forks—spring preload, rebound damping, and compression damping. Spring preload is the amount of applied load on the fork spring via the adjuster; rebound damping determines the speed at which the fork returns on its upstroke; and compres- sion damping determines the amount of fork travel during the downstroke. Not all forks share the same adjustable features, so consult your owner’s manual to see what settings your bike’s forks have. Spring Preload As mentioned in last month’s article, preload is the amount of load placed on the spring that resides inside the fork tube. In short, more preload reduces the spring’s springiness (by compressing it) whereas less preload increases its springiness. Preload adjustments are always found on the top of the forks and are adjusted using a socket or wrench (Figure 1). In general, turning the adjuster clockwise increases preload while turning it counterclockwise decreases it. The adjusters are usually integrated into the fork cap and are sometimes differentiated by anodized color. The preload adjuster may have adjust- ment lines machined into it for convenience in com- paring the two forks for evenness. As discussed in last month’s article, preload is initial- ly used when setting sag. Sag is the difference between the suspension being fully extended (no rider) and nat- urally compressed (with rider). If the sag cannot be set correctly using preload, you must install different springs to correct the prob- lem. Trying to compensate for an inadequate spring by adding preload to it will make the front suspension very harsh. When you install new springs, be aware that the OEM preload spacer needs to be cut to the appropriate size, otherwise the spring will have far too much initial preload on it. The goal is to ensure that the preload adjustment is somewhere in the middle of the range to allow you to make adjustments for different riding conditions. Preload can be manipulated for various riding conditions such as the track, rough roads, or the freeway. For track riding, preload should be added if the front suspension dives excessively during hard braking. A more accurate way of assessing dive is to attach a thin zip tie around the center of the fork slid- er tube. Make sure that it slides easily but is not sloppy. The zip tie will allow you to see how much of the fork travel you are using. If after a session of riding you see that the zip tie is firmly against the dust scraper or axle cast- ing, then the fork is bottoming out. In that case you need to add more pre- load, and then check the zip tie again. If the zip tie rests within 5mm of the dust scraper or axle casting, this indicates that you are using almost all of the available fork travel. On various OEM forks, sometimes what appears to be a preload adjuster is a fork ride height adjuster, so again check your owner’s manual. A ride height adjuster can only be used to alter the geometry of the bike by raising or low- ering the front ride height. To make the bike turn quicker, remove ride height by turning the adjuster counterclockwise. To make the bike turn slower, add ride height with clockwise rotation. Rebound Damping Rebound refers to the fork returning (its upstroke) after being compressed. The rebound damping adjustment controls the speed of this upward motion. Motorcycles 101 The rebound damping adjuster is usually located in the center of the preload adjuster (Figure 2), and usu- ally requires a flat-blade screwdriver to make adjust- ments. Sometimes the adjustments are measured in clicks, other times in degrees of turn. OEM stock set- tings are usually in the middle of adjustment. Turn the rebound damping adjusters clockwise on both forks until they stop. Write down how many turns/clicks this took so that you know where you started. Then take the rebound adjustment counter- clockwise all the way out on both forks so that you know how much total adjustment there is. With the adjustment all the way out, fully engage the front brake to lock the wheel then push down vigorously on the forks. Do not release the front brake while doing this. As the forks begin their upstroke, let them move naturally and observe the action of the fork. The stroke may come up then go back down, and may even start to come up again (the pogo effect). Adjust the rebound all the way in on both forks just shy of the end of adjustment, then repeat the pump- ing action with the front brake fully engaged. The upstroke of the forks will occur much more slowly now. The rebound action should be between these two extremes—the fork should rise to the top of the first rebound stroke and stay there. Work the adjusters on both fork legs until this is achieved, keeping in mind that both fork legs should be set the same. Compressio n Damping Compression damping manages fork travel during its downward (compression) motion. The compres- sion damping adjusters are usually found on the underside of the fork or above the axle (there should be a hole in the axle to allow you to access the adjuster), or close to the brake calipers at the bottom of the fork (facing the rider, Figure 3). Usually a flat- blade screwdriver is used to make adjustments. Sometimes the adjustments are measured in clicks, other times in degrees of turn. OEM stock settings are usually in the middle of adjustment. Turn the compression damping adjusters all the way in (clockwise) on both forks and write down how many turns/clicks it took so you know where you started. Turn the compression adjusters all the way out on both forks so that you know how much total adjustment there is. With the adjustment all the way out, fully engage the front brake to lock the wheel then push down vigorously on the forks. Do not release the front brake while doing this. With the adjustment all the way out (the least amount of com- pression), the forks should compress fairly easily. Adjust the compression all the way in on both forks, then repeat the p ump- ing action with the front brake fully engaged. The forks will not travel as far on the compression stroke and will feel rigid. As opposed to setting the rebound damping, setting the compression damping is subjective—you have to go by feel. Compression damping should be between these two extremes. The correct compression damping will provide you with the plushness or degree of firm- ness you need. Once you grasp this concept, you will be able to manipulate the compression damping on the side of the road in just a few seconds to provide you with the suspension travel you ne ed for the environment you are riding in. However, riding on the track requires setting both preload and compression damping in tandem to ensure that the front wheel tracks cor- rectly to the point that it inspires confidence. Next Month Next month’s article will discuss suspension adjustments for the rear shock. FZ Dave Moss started riding in 1974. He currently works with Bay Area Yamaha (formerly Redwood City Yamaha) helping new bike owners set up their bikes as well as providing chassis geometry/suspension classes for cus- tomers at the dealership and at track day events with local groups. The compression damping adjusters are located near the axle and can be made with a flat-blade screw- driver on most bikes. A flat-blade screwdriver is all that’s necessary to make rebound damping asjustments on most bikes. Figure 2 Use an open-end or socket wrench to adjust spring preload. As with all settings, both fork legs need to be set the same. Photos by Dave Moss. Figure 1 Figure 3
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Transcript of Adjustments+ +Forks
8/3/2019 Adjustments+ +Forks
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April 2004 FRICTION ZONE
Suspension AdjustmentsPart 4—Forks
y Dave Moss
Editor’s note—This month’s article is aimed at riders
ho frequently work on their own motorcycles. If youave any doubts about your ability to perform the proce-ures described here, please take your motorcycle to aualified mechanic.
THERE ARE THREE SETTINGS that can be adjusted onforks—spring preload, rebound damping, andcompression damping. Spring preload is the
mount of applied load on the fork spring via thedjuster; rebound damping determines the speed at
which the fork returns on its upstroke; and compres-on damping determines the amount of fork traveluring the downstroke. Not all forks share the samedjustable features, so consult your owner’s manual toee what settings your bike’s forks have.
pring PreloadAs mentioned in last month’s article, preload is the
mount of load placed on the spring that residesnside the fork tube. In short, more preload reduceshe spring’s springiness (by compressing it) whereasss preload increases its springiness.Preload adjustments are always found on the top of
he forks and are adjusted using a socket or wrenchFigure 1). In general, turning the adjuster clockwisencreases preload while turning it counterclockwiseecreases it. The adjusters are usually integrated intohe fork cap and are sometimes differentiated by nodized color. The preload adjuster may have adjust-
ment lines machined into it for convenience in com-aring the two forks for evenness.As discussed in last month’s article, preload is initial-
y used when setting sag. Sag is the difference between
he suspension being fully extended (no rider) and nat-rally compressed (with rider). If the sag cannot be setorrectly using preload, you must install different springs to correct the prob-m. Trying to compensate for an inadequate spring by adding preload to it
will make the front suspension very harsh. When you install new springs, beware that the OEM preload spacer needs to be cut to the appropriate size,therwise the spring will have far too much initial preload on it. The goal iso ensure that the preload adjustment is somewhere in the middle of the rangeo allow you to make adjustments for different riding conditions.
Preload can be manipulated for various riding conditions such as the track,ough roads, or the freeway. For track riding, preload should be added if theont suspension dives excessively during hard braking. A more accurate way f assessing dive is to attach a thin zip tie around the center of the fork slid-r tube. Make sure that it slides easily but is not sloppy. The zip tie will allow ou to see how much of the fork travel you are using. If after a session of ding you see that the zip tie is firmly against the dust scraper or axle cast-
ng, then the fork is bottoming out. In that case you need to add more pre-oad, and then check the zip tie again. If the zip tie rests within 5mm of theust scraper or axle casting, this indicates that you are using almost all of thevailable fork travel.On various OEM forks, sometimes what appears to be a preload adjuster isfork ride height adjuster, so again check your owner’s manual. A ride heightdjuster can only be used to alter the geometry of the bike by raising or low-ring the front ride height. To make the bike turn quicker, remove ride heighty turning the adjuster counterclockwise. To make the bike turn slower, addde height with clockwise rotation.
ebound DampingRebound refers to the fork returning (its upstroke) after being compressed.
he rebound damping adjustment controls the speed of this upward motion.
Motorcycles 101
The rebound damping adjuster is usually the center of the preload adjuster (Figure 2ally requires a flat-blade screwdriver to mments. Sometimes the adjustments are mclicks, other times in degrees of turn. OEMtings are usually in the middle of adjustme
Turn the rebound damping adjusters clo
both forks until they stop. Write down turns/clicks this took so that you know started. Then take the rebound adjustmeclockwise all the way out on both forks sknow how much total adjustment there iadjustment all the way out, fully engagebrake to lock the wheel then push downon the forks. Do not release the front bdoing this. As the forks begin their upstrokmove naturally and observe the action of thstroke may come up then go back downeven start to come up again (the pogo effe
Adjust the rebound all the way in on botshy of the end of adjustment, then repeat ing action with the front brake fully engupstroke of the forks will occur much mnow. The rebound action should be betwtwo extremes—the fork should rise to thefirst rebound stroke and stay there. Work thon both fork legs until this is achieved, mind that both fork legs should be set the
Compression DampingCompression damping manages fork tr
its downward (compression) motion. Thesion damping adjusters are usually foununderside of the fork or above the axle (thbe a hole in the axle to allow you to adjuster), or close to the brake calipers at of the fork (facing the rider, Figure 3). Usblade screwdriver is used to make aSometimes the adjustments are measuredother times in degrees of turn. OEM stock
usually in the middle of adjustment.Turn the compression damping adjusters
in (clockwise) on both forks and write down how many turns/cliso you know where you started. Turn the compression adjusters out on both forks so that you know how much total adjustment ththe adjustment all the way out, fully engage the front brake to lockthen push down vigorously on the forks. Do not release the front doing this. With the adjustment all the way out (the least amoupression), the forks should compress fairly easily.
Adjust the compression all the way in on both forks, then repeating action with the front brake fully engaged. The forks will not ton the compression stroke and will feel rigid. As opposed to rebound damping, setting the compression damping is subjective—to go by feel.
Compression damping should be between these two extremes. compression damping will provide you with the plushness or degr
ness you need. Once you grasp this concept, you will be able to the compression damping on the side of the road in just a few provide you with the suspension travel you need for the environmriding in. However, riding on the track requires setting both pcompression damping in tandem to ensure that the front wheel rectly to the point that it inspires confidence.
Next MonthNext month’s article will discuss suspension adjustments fo
shock. FZDave Moss started riding in 1974. He currently works with
Yamaha (formerly Redwood City Yamaha) helping new bike owtheir bikes as well as providing chassis geometry/suspension clastomers at the dealership and at track day events with local groups
The compression damping adjusters are located near
the axle and can be made with a flat-blade screw-driver on most bikes.
A flat-blade screwdriver is all that’s necessary tomake rebound damping asjustments on most bikes.
Figure 2
Use an open-end or socket wrench to adjust springpreload. As with all settings, both fork legs need tobe set the same. Photos by Dave Moss.
Figure 1
Figure 3
