09 450 shock weirdness

1 reply to this topic

Posted March 24, 2015 - 10:50 PM


I have the shock off the bike with the spring removed. I was playing around with the rebound clicker, compressing the shock then watching it extend and discovered that when I increase the rebound it makes the shock much harder to compress. I have to go to 7 clicks out before I can easily compress the shock. Why is the rebound clicker making it harder to compress? It doesn't seem right.

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Posted March 24, 2015 - 11:03 PM


Never mind. I found this by grayracer (who else) :worthy:


I should search before I ask.


Here's the thread,   http://www.thumperta...ebound +clicker




The compression adjuster on either the fork or the shock (and either compression adjuster on the shock) has no effect on the rebound directly because it controls the bleed circuit on a valve assembly that doesn't have any influence on rebound. That is not the case with rebound adjusters, since the fork mid valve and the shock compression stack (at least in the case of contemporary KYB and Showa units) bleed through the rebound adjuster. But as I said, the rebound adjuster has a much greater influence on rebound than compression for the reasons I went over.

With any of the adjusters, what they actually do is to control the size of an oil circuit that allows oil to bypass the valve they are connected with. The effect is that as this circuit is opened up by backing out the adjuster needles, the valve assembly can move at a faster speed before there is enough pressure to lift the shim stack and open the ports in the piston. Once that point has been reached, the bypass controlled by the adjuster very quickly becomes almost or completely ineffective. In fact, as the speed of the shaft is increased, the oil velocity through the bypass will eventually reach a maximum, and if the oil pressure is significantly increased beyond that point, the circuit will "lock up" hydraulically, somewhat like a traffic jam, and the flow will be reduced dramatically, handing off the excess to the valving.

In the KYB fork, there is one rebound and one compression adjuster. To the extent that they control any particular valve, these influence both the high and low speed elements of the stack. It's probably true that the clickers on the fork have more effect on the low speed operation than on the high speed because of the locking phenomena just mentioned, and because the major effect of the clickers is to delay the operation of the valve stack. The higher speed elements of the stack will be less affected.

The rebound in the KYB shock will effect both low and high speed elements of the rebound and main compression stack. The shock low speed compression adjuster has a very minor influence on high speed compression, while the high speed adjuster has virtually no influence on low speed.

Also remember that "speed" in reference to damping units refers to the speed at which the unit is being compressed or extended.

Edited by MAD_POTTER, March 24, 2015 - 11:08 PM.

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