on my twin shocked dakar replica I am using 420mm eye to eye length shocks, these have 100mm max compression, a spring length of 272 by 50mm wide. I have tried the following spring weights 50kg/cm, 45kg/cm ad a variable 25 / 35 / 40 progressive spring. I found the 50s rock hard, the progressives to soft and the 45s are firm but allow about 70mm of suspension travel in normal road and gravel track riding ( so leaving 30 mm for harder use before bottoming out onto the rubber grommets in much harder use) and give a fairly comfortable ride that is with 10 mm of pre compression on the spring settup length. They can be wound up a bit more for luggage etc and also have 22 clicks for each of the option of high low speed compression as well as rebound. I did consider trying a shorter 200mm 45kg/cm mixed up with a 70mm 40kg/cm starter spring to see if that takes a little of the initial firmness out of the ride but have not got round to that at the moment. I am not sire of the exact working here but i assume that 2 x 70 / 45/kgcm come in at 90/ kg /cm but that would be plus or minus some equation for there being two shocks as opposed to one and associated drag / friction/ damping / acceleration and deceleration or whatever- so then its back to the boffins and the blackboard. You also have to take into acount as the longer swing arm gives much more travel and leverage on the whole back end and the therefore sits at a steeper angle ( ie 13.5 mm from centre line in the case of my bike giving 230mm travel at the axle) then the exact positioning on the swing arm of the mount is critical but you also need to take into account that changing angle of the shock absorber as it compresses and the swing arm moves up changing the angle the suspension is moving and operating in throughout the arc of travel, get it wrong and you will end up bending your shock absorber or not maximising the shock absorber in its best operating area. There will be a pay off at the extreme ends of the travel where the shock is working at a limited amount of its ideal damping range.
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adventure950 screwed with this post 10-04-2012 at 05:36 AM