weights and measures

[Zillr]

Well it appears one thing everyone agrees upon is that spring rate is the first order of business followed by preload, and finally damping (the hard part). Hope the sprung unsprung weight is a fly in the ointment. I have been living w it since 2001 when I took delivery of a 996 w springs that appear to me to be for about a 200lb load. I figure I was 165+~15=180. At some point I put mags on the bike but never thought much of it's handling. Seemed stiff. Wobbled. May have been damping and or spring rate. I have got it working pretty well now but only by chance it seems, hitting on a good combination of adjustments. I can look back at my record and see the way it was delivered and all subsequent adlustments including doug polen's recommends were not as now. The new Pirelli corsa IIIs seem to want more pressure than stock. Rear spring rate -21/75 7.5 Nm I believe and I measured the frt springs to be about 1kg/mm I think. I calculated that the springs were about 10 % too stiff for me, excepting any argument about weight ratios. based on general consensus. Thanks for all the input,, did not know of the swing arm dimension diff. I am going to do some dynamic testing now I believe. Ciao

[Zillr]

Hey C Weld, Sorry I lost track of this dialouge for so long. I am just now really looking at the forum a bit more and see features and ways to navigate that I had not appreciated previously. Since I posted regarding this, I had thought about the basic question of wether change in sprung/ unsprung weight calls for spring change, and conclude I was all wrong. Looking at your post I would say you hit the nail on the head. The fallacy in my thinking
is in considering wheel speed. The thing that matters is energy. The wheel may be more responsive, have a higher speed at some point in it's travel, but the net energy is still the same because the wheel is lighter. The same spring will bring it under control, and another way of stating that is in your words below. The spring is there to hold up the sprung weight. I remember thinking that seems intuitive but looking at spring charts and not knowing about mag swing arm, got my self convinced of folly. Likewise to Shazaam and his physics demonstration. Thanks for the input. Rad

Originally Posted by seespotweld

another fly in the soup ...not sure if I agree about the spring rates needing to increase ..for one thing I think the mag swingarm is longer than the stocker which would give the wheel more leverage making the heavier spring necessary . My understanding of the primary roll of the spring is to support the weight of the bike/rider ..this has not changed much . Most suspension setup articles I've read say the first thing you do is set the spring sag and then they move on to damping.I don't think the spring has much to do with controlling movement ,well of coarse it's part of it but the speed of said movement is handled by the damping.

[Zillr]

I see the folly of my thinking. Thanks for the physics, Shazaam. I realized thinking on it later, the wheel speed may be faster at some point in it's travel, but the energy is unchanged as the mass is reduced. Net effect is the same spring will bring it under control. and I like the way Seespotweld puts it. The spring is there to hold up the sprung weight. Thanks also Old Baldy for your observation. R