rear suspension rocker ratio....

[andy9980]

There are numerous different shaped/angled rear rockers for the various models all giving a different ratio.......so does the ratio change with the angle that either the shock or tie rod come at it does this alter when you lengthen or shorten the tie rod?

[Dennie]

Hi Andy,

The ratio of the rocker will be the same, only the angle that the shock makes with the linkage will change. When you increase the length (the linkage) all three angles must change (math). I have made a picture of the 749R setup. You can see clearly the triangle made between the rocker, shock and linkage.

Dennie

[andy9980]

So what would happen to the ratio if you raised the pivot point mounting of the rocker up say 1 inch lengthened both the tie rod and the shock eye would that effect the rocker ratio? sorry if im being dum...

[Dennie]

Originally Posted by andy9980

So what would happen to the ratio if you raised the pivot point mounting of the rocker up say 1 inch lengthened both the tie rod and the shock eye would that effect the rocker ratio? sorry if im being dum...

Hmmm....I think when the shock is placed under a wider angle as shown in the picture, the shock get a lesser load. Therefore the xx9 bikes have a softer spring then the 749R. So the more vertical the shock is placed, the more linear it becomes and thus resulting in a higher load and the need for a stiffer spring.

I also don't think that in- or decreasing the tie rod length will change the linear behaviour of the shock. The pivot point of the swingarm is not the same as the shock/tie rod.

[andy9980]

Originally Posted by Dennie

Hmmm....I think when the shock is placed under a wider angle as shown in the picture, the shock get a lesser load. Therefore the xx9 bikes have a softer spring then the 749R. So the more vertical the shock is placed, the more linear it becomes and thus resulting in a higher load and the need for a stiffer spring.

I also don't think that in- or decreasing the tie rod length will change the linear behaviour of the shock. The pivot point of the swingarm is not the same as the shock/tie rod.

so specifically to the 1098 set up...........why would they shorten the shock length by what 8mm when you use the corse rocker? is tat just to get it to fit or for something to do with the ratio?

[Dennie]

Originally Posted by andy9980

so specifically to the 1098 set up...........why would they shorten the shock length by what 8mm when you use the corse rocker? is tat just to get it to fit or for something to do with the ratio?

I don't know about the 1098 setup. I can imagine that the rocker ratio will result in a more linear shock. Just like the 749R it could have a shorter stroke. If the stroke is indeed shorter, why not make a shorter shock? This will save a few grams.