Torben Borrowy: In general rear shocks work perfectly within a wide range and can be fine–tuned with the adjustments of the rebound and compression clickers, and the spring rate (change of the coil spring or adjustment of the air pressure). On the extreme ends of the weight range mentioned above, you compromise a bit of performance but the compromise is still hard to notice.
Explain why the optimum shock for a bike might (assuming average rider weights) be right for some riders yet too hard or too soft for others?This is where riding style and the terrain you ride in comes into play. If you have a very dynamic or active riding style and blasting through berms is your deal you want more support on the low speed compression damping, if you are looking for the maximum comfort you might find such a setting too harsh. On the rebound side of things it also makes a difference if you are riding on a man–made hard–pack soils where you want the suspension to feel very settled, while a natural, rocky alpine trail requires a more active or lively setting to adjust to the bump frequencies. Also more aggressive riders benefit from more ramp–up in the spring rate while a linear curve offers more comfort.
Terrain, rider style, come on Torben! Surely there are enough dials on a modern shock to compensate for different people?That is correct. The range of adjustments is pretty big and on high–end shocks you can find multiple ways to fine–tune your shock without having to open it. It is always key to have the correct base tune for the bike. The number of adjusters on your shock should be very minimal if you just want to swing a leg over your bike and ride, if you want to fine–tune your shock and spend some time finding the optimal set–up you should go for the full package of adjustment options.
I guess the message here is that riders buying after–market should buy correct to begin with right? How should they go about this?As mentioned above, the right base tune for your bike is key. The RockShox dealer should be able to help out here. He can always rely the knowledge of the SRAM Tech Centre and complicated cases will find their way to our computers.