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I'm pretty basic but for me the pre load sets the suspensionfor the weight of the bike plus what your individual weightand load is so that the suspension is at the optimal startingpoint in it's stroke to have a full stroke, damping controls the stiffness.Maurie.
Preload delays when the spring rate begins but doesn't change the spring rate. More preload = more initial force to move the spring. Once the spring starts moving the rate is the rate (if a Single Rate spring). As Wayne says preload can impact the design of a shock system that has a dual rate or progressive rate spring. And I think that's the real consideration; you can't look at preload in isolation. It impacts the geometry of the entire motorcycle so in some situations more preload/less rate is better and in some more rate/less preload is better. That's why taking you and your bike to a pro is always the best idea...
Preload delays when the spring rate begins but doesn't change the spring rate. More preload = more initial force to move the spring. Once the spring starts moving the rate is the rate (if a Single Rate spring).
to a point where the spring will "feel" 150 kg of load
Glad you raised this Huzo. I have been struggling to understand whether I need heavier or lighter springs on my Mark IV, using the original Koni / Ikon rear shocks with progressive springs. Currently I use the full travel on the rear shocks with pre-load set to the highest setting, and I reckon the suspension is a bit harsh, especially on the crappy secondary roads around here. I'm a lightweight ( but not as light as I used to be !) at around 65 kg ( 140 lbs to those Stateside).I'm thinking I might be better off with stiffer progressive springs with minimum pre-load rather than what I have at the maximum pre-load, to give a more compliant ride, with the added bonus of being less likely to bottom out. I figure softer springs will make the ride compliant too, but will be even more likely to bottom out. Do you reckon I kidding myself?
In the first instance the spring will "feel" 170 kg of force, not 150 and in the second instance it will "feel" 190 kg. So in these two cases the spring is not in an identical state, it is compressed more in the second case and will not react the same.
With a normal spring I believe preload adjust only sets the height. Add load, adjust the preload to get the right height, and the spring is still going to react the same (though the added weight will dampen the ride)
Changing preload does NOT change the effective spring rate . Didn't we settle this like 2 months back ? Dusty
Oh dear, if we did I've either forgotten or I didn't follow the thread. What was the title Dusty, do you remember? I'll search it if I can.
Actually Huzo , I was going to pull my post , you quoted me first so ... Anyway , apologies . Dusty
Ok guys my question will sound either simple or dumb after reading all this. Let's us me and my 07 Calvin as the example. I weigh 160 and ride with no passenger. If I want the bike to squat a little lower when I mount her would I shorten the spring or back it off?
Yeah good start Maurice I agree, but following your explanation, wouldn't an alteration of the pre load, just put the damper at a different part of it's stroke ? ie alter the ride height and bugger all else ?
A springs rate is it's rate it doesn't change. A Damper controls theSprings movement at either end of it's useful travel. The Pre-Loadsets the suspension at the ideal height for Damping to be most effective.
Does the CalVin have rear preload adjustment, or just damping adjustment?
An excellent explanation.What's also correct but perhaps a little hard to initially accept, if you shorten the spring by cutting it, the spring rate increases. Conversely, place two identical springs in series and the overall spring rate is halved.