Jasper wroteWhich position gives which result?
Jasper-- Here is a cut and paste from an old thread I started covering my restoration of my '91 AMA Ferracci Corse. It is a bit wordy but it covers your options.
"short answer- it depends upon how flat a progressive rate you like (I prefer the term leverage rate because you are really looking at a changing leverage ratio through the arc of the swing arm and rocker), where the rear axle is located (which is a big consideration with the leverage), the stiffness of the spring you chose, the type of trackbumpy or smooth, and the rear ride height you want and more I am sure.
But if you are going to put the bike on the track my recommendation is- when looking at the rocker from the right side of the bike- place the shock bolt at any position between 6 to 9 o'clock. This side of the adjustment gives you the flatter rising rate curves because the spring/shock is closer to 90º (perpendicular) to the swing arm. These flatter curves are what most modern track bikes use because they resist squat and works better mid-corner. These positions will also raise your ride height so pick a hole accordingly.
Looking at the pictures you can see that most race bikes I have bought have the shock bolt around the 6:00 positionthis puts your ride height at maximum and the rising rate at the middle adjustment.
If you want to start with a position John Hackett suggests--- then when put the bolt hole at the 8 o'clock position. I have used this position on one of my track bike -- using the mono ball bolts to make any changes in ride height. I have also used the bottom adjustable Mono ball bolt on my shock but that is a real pain to do. I only change my sprocket by 1 tooth at most on this bike so the axle does move much so the leverage stays about the same and I can keep that position from track to track.
If you are going on the street you may want a bigger curve-- so pick a hole on the right side of the clock which tilts the shock/spring more forward. Pick a hole that gives you the ride height you like as a baseline and then adjust at the hoop. Mike C reminded me that the street bike came with the bolt hole at the 3 o'clock position-- good for bumpy street roads- but I think it was even too progressive for a street bike."
