Originally Posted by
Sy Reene
Not sure of the science behind it.. but I'd hazard to guess that the amount of torque req'd is somewhat dependent on the surface area of the clamp portion that is compressing against the saddle's rails. A clamp that spreads the compression over a larger platform area, has a different ability to clamp (for a given torque on the bolt) than a clamp where the compression is confined to smaller clamp area. Likewise, a smaller-area clamp type, is focusing the compression to a smaller area obviously, perhaps making it more difficult (or unnecessary) to torque as much without damage to the rails. ie. smaller clamp = more biting force? Somewhat a PSI thing..
Ignoring the rails for a bit... Basically what the big S has done with their seat posts is put two cones on either side of a round hole. You have to torque it up that hight to get enough pressure on the cones to create enough friction to keep the saddle from rotating up or down. I like the idea, position infinitely adjustable and you don't have to do the whole loosen one screw, tighten another dance.
I'm sure the actual PSI on the rails is much lower as a lot of that is going to be applied to the interface with the seat post, but when you go from a two bolt system that works just fine at like 5Nm, having to torque a bolt down to 12-13Nm just seems scary.