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Speed Wobbles

3K views 23 replies 18 participants last post by  Tdub 
#1 ·
So, I was on the freeway today and went WOT in 3rd at around 60mph and experienced my first speed wobbles. Scared the hell out of me! Now what confuses me is that on the on-ramp I went WOT in 2nd around 40mph and had no headshake whatsoever. What could have caused this? I recently had new tires mounted and they were aligned and balanced, and I also have balance beads..
 
#3 ·
Front end got light then either you held on to tight or you rolled off the throttle
 
#7 ·
YOU caused it. too much input on the bars. most likely in an attempt to hold on tight while you went WOT on a public road. if you relax your arms and have no upper body weight on the bars, you won't have any more head shake...


s3aturnr
 
#18 ·
Too tight on the grips, or too loose on the grips can do it too bud.

First sportbike ever, honda cbr 600, 3 years ago, was doing 65 on the highway and went no hands to stretch the back, next thing i knew the front tire was doing the chickin, and I filled my pants.

relaxed grip is the way to go sir!
 
#19 ·
Yup, too much grip/weight on the bars.
 
#20 ·
If you get speed wobbles while off the gas and no hands on the bars, it's because you are off the gas. Not because of anything else other than a bump perhaps. Remember that the bike has rake designed into it for directional stability. But as with most sport bikes the rake is a fairly small amount. So the tire has very little directional stability in general. The only thing that really keeps the tire in line is it's inertia, hence the gyroscopic effect. Being on the gas unloads the front end allowing it to react in the manner in which it was designed, but also makes inputs easier to manipulate the tire. The grip from hell fights the natural movement of the tire over road imperfections. This in turn leads to a deflection in the opposite direction, which cycles and repeats.

When wobbles occur off the gas and with no hands on the bars it's very much the same thing. The difference is that instead of an opposing input at the bars, it's the weight transfer over the front tire that is exacerbating the issue. The front tire while decelerating becomes weighted down beyond it's static load. This adds force to the suspension and when a bump is hit, it reacts similar to holding the bars too tight. The tire deflects and is slow to react but once it gets moving, it moves too far in the opposite direction. The tire again deflects and is impacted by the road imperfections and the cycle repeats. In general having a light grip on the bars would eliminate that issue, also being on the brakes would again counteract the issue. Mostly because the energy would be transferred through the bike differently. While on the brakes the suspension goes through a major geometry change, making the issue become a different beast. This is why a bike is unstable ( usually while hard on the brakes ) and the rear tire will wallow around. Because so much weight is on the front tire, instead of it moving, the now lighter rear part of the machine moves and shifts under the inputs.

A good way to test this theory is to get up to a normal speed and let off the gas. Then let the bars go. Then with one hand give one of the bars a solid whack. The bike should go into a speed wobble. It should also quickly sort it'self out. Not an idea of fun, but you can do it on your bicycle as well.

The wobble is a needed and appropriate reaction from the machine. It will almost always work it'self out if allowed to do so. This is why it is said to let the bars go when one occurs. This is so you don't fight it. The speed wobble is not a bad thing, but it's not a good thing either. It is a needed reaction in order to deal with the problem that created it, but it is non productive to directional control too. There are two ways to eliminate a wobble. One is to let the bars go and or relax your grip on them. The other is to get on the gas harder to unload the front end even more and hopefully arrest the wobble. The later is difficult for beginners and is difficult to do on bike without lots of power. Even a 600cc machine can be under powered to deal with it with the second approach. The easiest way to reduce the potential for a wobble is to maintain a feather grip on the bars and remember to relax even more when one does occur.
 
#22 ·
Some use beads instead of wheel weights
 
#23 ·
i heard steering dampers can help this problem, but thats only what ive read :p
 
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