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Shock adjustment/spring preload.


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Could somebody tell me in layman's terms the relationship between the shock absorber adjustment and the rear spring preload adjustment on my '04 RT?


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The spring preload is located behind the right triangular cover, just below the seat. Adjusting the knob clockwise will add spring preload. This is done when adding weight to the bike (passenger or baggage) or to firm up the suspension.

The dampning adjustment is a screw behind the left footpeg cover. There is a hole to access this screw in the cover and you will need a long straight blade screwdriver. Turning the screw clockwise will add dampning. Turn only a 1/2 to 1 turn at a time and give the bike a ride between adjustments to feel the change. A good way to start is to find the original setting for future use. Count the number of turns clockwise until the screw bottoms (DO NOT tighten the screw, stop when resistance is felt!) Now back the screw out to where you started and write down the original setting for reference. Adding dampning will slow the reaction of the shock return after hitting a bump.

Hope that this helps!


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Basically this is at least 2 issues when using the standard rear shock.

Adjusting the knob under the right-hand side panel will either a/. Compress or b/. Allow the spring to extend. The spring comes from the manufacturer at a given spring rate. This means that it is set up to allow the bike to ride level when it has the lightest of light rider, right up to mr & mrs lardy! So when you are carrying more weight, the back end of the bike wants to sag, but you compensate for this by compressing the spring with that knobby thing under the side panel, and therefore the loaded ride height is recovered. However you must bear in mind this is all an engineering compromise.

Now the other issue is setting the damping with the screwdriver slot at the bottom of the shock absorber. This has the ability to allow the rear wheel to track up and down as well as possible to suit the kind of roads and riding style you use.

Some surfaces are very course undulations and the shock absorber will need to move and recover as quickly as possible to allow the wheel to remain in contact with the road for as much time as possible, but conversely this will have an effect on smoother more boingy sorts of roads. Really Posh shock absorbers (most of us don't have them) - have adjustment for compression and rebound damping standard only compensates for one.

So the bottom line is: set the spring preload under the side panel, so that the bike ride height is level, but not so hard that it is forcing it up against its top stops with you sat on it (that would ruin everything).

Then go and find some roads you like to have fun on and take the appropriate screwdriver with you. Ride the road then make a little adjustment in one direction and ride it again - note the difference and keep changing the setting until you find the bike rides the best. It sounds long winded, but is worth it, because you will find that:

a/. you will be able to ride the road faster.

b/. you will be able to ride it safer.

c/. Your tyres will probably last longer.

d/. Oh bound to be loads more benefits.

Let us know how you get on.


Andy thumbsup.gif

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Could somebody tell me in layman's terms the relationship between the shock absorber adjustment and the rear spring preload adjustment on my '04 RT?



kruuuzn, to understand what does what & why you first need to understand how that rear spring/shock works..


There are a few things in that rear shock/spring package that effects what you feel when you ride down the road & how the system recovers when you hit a bump..


First you have that wound coil spring- it has both a load & rate.. The spring RATE is the same at any compression or any collapsed position short of coil bind (the coils touching).. Next is the load (that is what holds the bike up).. When you turn the spring adjuster that changes the spring load & loaded height (that doesn’t change the spring rate though)..


Most people confuse spring load with spring rate.. They are NOT the same.. The load is usually figured at a given spring length & can change as the spring height changes (that’s what you actually adjust).. The rate is figured form wire diameter & number of turns & that is a constant regardless of the spring height (excluding coil bind as that removes working coils) . The spring rate is non adjustable,, the loaded height is adjustable.. Some springs are a variable rate or dual rate as the wire diameter can get thinner on the end coils or they are closer together so the end coils bind before the middle coils do..


Now on the shock absorber itself.. That operates just like the pneumatic cylinder on a screen door.. It has compression dampening, rebound dampening, inherent internal parts friction, blow off valving (to allow quick compression without damage or to prevent hydraulic lock up on quick shock compression), & in some cases by-pass valving or extra by-pass holes/restrictions..


The part you CAN adjust on that is shock rebound dampening (internal oil flow restriction that limits shock return to full extension).. For most non racing applications a lot of shock packages only offer rebound dampening adjustment.. Seeing as the spring RATE is the same at about any nominal load the compression dampening in the shock can be pretty constant.. Heavier loads on the rear of bike can effect that slightly but hopefully the spring is adjusted to raise the bike back up to compensate.. Now the rebound action on the shock is adjustable & can be rider adjusted to allow a slower return to nominal ride height (that can keep the rear of the bike from jumping around like pogo stick).. Or loosened up to allow a fast return to nominal ride height (that allows a quick return & softer ride but can give loss of some rear wheel control.. Too much rear rebound control & the wheel can bounce right off the road (especially on chatter bumps or square edged impacts) , too little rebound dampening can allow a very uncontrolled rear suspension (act like a worn out shock)..


Now the above is a very simplistic view but should give you enough info to set yours correctly.. Just ride & adjust..



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