YellowDuck Posted June 7, 2015 Report Share Posted June 7, 2015 As requested...here you go. I have so much to post here - this really is my favorite topic by far. Can we start with preload? This is truly my pet peeve. It is so poorly understood by 75% of riders, and you can always find someone who completely misunderstands it but will argue until they are blue in the face that their view of it is correct. The big misconception is that, when you add preload (turn the preload adjuster in), you somehow compress the spring and make the suspension firmer. A huge fraction of riders labor under this misunderstanding. What really happens is that, when you add preload (say, 3 mm), the suspension simply extends by exactly that amount. So, your starting sag position is 3 mm higher, and you will have 3 mm more positive travel before it bottoms out. The spring compression does not change. The only condition under which the suspension is made "stiffer" with added preload is the situation where the suspension is fully extended (e.g., full extension of the forks when the front wheel is off the ground). It will take more weight on the suspension to get it moving from the fully topped-out postion, but once it has any compression the spring rate is the same as it ever was (e.g., it will compress 1 mm for each 10 N (1 kg) of weight, if it is a 1.0 kg / mm spring). Obviously we don't spend too much time with the suspension topped out, so suspension stiffness under that scenario is not terribly important. So, what preload really does is set the initial ride height and sag - it determines the ratio between available positive travel (compression) and negative travel (extension). That's it. It does not make the suspension firmer. When you start talking about rear suspension, the average rider's understanding of this is even more incorrect. Because of the rising rate linkage ratios on most bikes, adding rear preload (and therefore extending the rear shock and increasing the swingarm angle) will actually make the rear suspension action *softer*. Yes, softer. Even some well-known suspension tuners speak incorrectly about this issue, saying, for example, that when you add fork preload you also should increase rebound damping to help control the "extra energy stored in the spring". What's really happening is that you probably needed the extra preload because your corner speed was increasing and you were running out of positive travel. It was *you* and your high-G cornering putting the "extra energy in the spring", not the preload adjuster. If anyone would like further explanation of preload and how it works, I have links I can share. There are some complicated exceptions to the basic picture above, especially when dealing with suspension where the topout springs are regularly engaged...but that is not Preload 101, that is the Master Class. Quote Link to comment Share on other sites More sharing options...
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