After an interesting experience this weekend (a violent tank slapper) I suddenly gained a great deal more interest in my bikes suspension and the various ways it can be adjusted. I came across some interesting and useful information on the internet and I would like to share some of it. There is a lot of great stuff here (enough material for a book) regarding suspension setup.
http://aprilia.rsvmille.home.comcast...tm#TANKSLAPPER
"TANKSLAPPER
Problem: A tankslapping bike feels unstable, especially when entering turns. The bars seem to "twitch" excessively whenever a midcorner bump is encountered. The bars often whip back and forth violently several times (or more) when A tankslapping bike is accelerating aggressively over bumps while coming out of a turn--in other words, a "tankslapper." The bike steers very easily, although a lack of traction is sometimes noticeable in the rear whenever he tries to accelerate at moderate lean angles. The bike also seems to have a dropped-down, "nose low, rear-end-high" attitude while riding.
Cause: If the bike feels this way, then probably there is too much front end weight bias
Solution: The biggest distinguishing factor in this case is the "nose-low/rear-end-high" chassis attitude feeling. . This not only hinders traction at the rear, but also affects the steering geometry (steeper rake/less trail) and can cause the instability problems. As long as the bike is suspension static sag levels set correctly, the first step is to try less rear spring preload and/or more front preload, to the point just before they begin to affect handling negatively; You should remember to adjust his rebound damping if necessary (in fact, he should check to see if decreasing the front rebound damping in small increments helps; the forks may be too stiff, hindering traction). If only partially successful, a more drastic step would be changing chassis ride height; this would involve raising the front end by dropping the fork tubes in the triple clamps (if there's enough material protruding above the top clamp, to ensure front fork structural integrity), and/or dropping the rear by shortening the rear shock (if possible).
Note: We've also seen a tankslapping tendency produced by too much rearward weight bias. The bike might try to be working the opposite of the preceding paragraph solution, or check out the understeer/no front traction problem scenario for more suggestions. "
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Well, sounds like great advice. I ended up dropping the ride height in the rear to one notch above the minimum and raising the ride height in the front to one notch below the maximum. I also backed off on the damping on most dampers to mid way between full soft and factory standard. I backed off on the front rebound slightly more than that.
I took her for a spin and goodness, she feels different. The bike is higher up front and lower in the back which makes for a more comfortable riding position. It feels more nimble and easier to flick around in the cut and thrust of city traffic. So, I am happy. Hopefully she will be less prone to tank slappers as well.
I think that the bike might be better on settings near factory standard for the track but I think the changes I made make good sense for street riding.
I reckon that since the manufacturer took the trouble to put an adjustable suspension on your bike and you have paid for it, then you should learn to make the most of it.
Also remember that your tires are an integral part of your bikes suspension so keep your tire pressures correct.
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Originally Posted by carbonhed
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