Monoshock Conversion

[bananas]

So I've been having trouble with my non-linkage monoshock setup.. I had planned to mount my shock to the top rail of my swingarm and the upper mount under my gas tank.. I picked up a non-linkage 2006 Ducati 800SS Sachs unit (dual-rate spring) because it is mounted in this way. So it turns out my GSXR 600/750 swinger has a hollow upper rail so for safety I didn't end up using it as the mounting point.

The shock is mounted to the swinger at the axle and the upper mount directly to a frame brace. I'm having problems with the shock being extremely soft. From what the Ducati guys are saying, I'm not getting much progressive travel.

So my question is: Does anyone know what formulas I should be using to calculate my mounting positions? I'd love to know what is actually going on with planning the suspension geometry so any supplementary reading would be awesome as well.


I had wanted to end up with something like:

Chappel Customs '82 CB985F (R6 linkage shock -- mounted direct)

Ducati 2006 800SS Sachs (Non-linkage)

Pictures from my build for reference:

 

[SONICJK]

If you mounted the shock further from the pivot point of the swing arm it should be less soft. As it sits the rear of the swingarm (and tire) will move several inches before the shock even has a chance to really compress.

 

[xb33bsa]

+1 that is it, you have too much leverage on the shock and too much wheel travel

 

[sav0r]

Even though we know what you mean, you need to differentiate spring rate and damping properties when speaking in terms of suspension. In your example, the shock isn't too soft, the spring however is. The guys above are right, you changed what is known as wheel rate. The ratio of wheel movement to spring movement has changed in a way that disadvantages the spring. Not only does this effect spring rate, it greatly changes the way the shock will apply damping force. If you haven't measure your wheel rate yet you should. You might not be able to even achieve an acceptable wheel rate if you didn't account for it in the first place.

 

[bradj]

Plus one on what everybody said here is my linkageless set up its it a buell shock & mathmaticly correct. Forget the formula becouce its been so long i have not worked on it in a year or better.

 

[50gary]

In your case (bananas) the more towards vertical the shock is mounted the quicker it will react, both spring and damper. You will have to move the upper shock mount rearward quite a bit. You might reconsider copying the Ducati set up. Reinforce the "tower" to withstand the force of the lower shock mount.
Cheers, 50gary

 

[SONICJK]

I would think that upper swingarm brave would be plenty strong to support the shock?
Why not just add some material to it to brace it if you don't trust it?