preload is the measurement that the fork spring is compressed by the spacer lenght and the lenght of the fork cap that screws inside the fork. The forks must be fully extended e.g the fornt of the bike jacked up so the wheel is off the ground or the forks out of the bike and fully extended. If for example when your fork is fully extended, you take a measurement from the the top of your fork leg (cap removed) to the washer that sits on your fork spring lets say if that measured 100mm and the threaded section from the bottom of your forkcap the underside of the lip measures 50mm you could assume that when the fork cap is screwed in there would be a void or space of 50mm, there for the spacer you would need for a 40mm preload on the spring would be 40mm plus the 50mm void which would mean a 90mm spacer. these are just measurements i made up to explain the process--hope it helps---grimster

 

yes it all makes sense now...I should have just done it myself...then I would have known whats been done in there. I guess I'll have to drop the legs out and check them...pita.

Thanks for the help
Fly