Head Shake... Why does it happen?

My theory on headshake is that you're turning slightly and applying a bit of bar pressure to counter steer into the turn, when the tire suddenly goes light due to a bump or acceleration. When the front end goes light, the bar pressure that held you into the turn now turns the wheel a bit more and when it regains traction you get the headshake until it sorts itself out. If you blow it bad enough, you get a tank slapper and get tossed off of the bike, like I did three years ago.

Back when I crashed, I couldn't understand what I had done wrong for a long time afterwards. As I continue to ride I get more understanding and now think that I know what went wrong and how to prevent it from ever happening again. There are two main situations when you're in danger, while accelerating, usually uphill, on a bumpy surface, and while leaned over in a bumpy corner.

Being aware of when you're in greater danger of headshake is often enough to prevent it or at least reduce it. But if you ride fast on twisty roads you can't avoid a little bit of headshake once in a while. Watch any road races at the top level and you'll see those guys dealing with it almost every lap.

Since I have a background of riding dirt bikes, it never used to really bother me, but now strong headshake brings back unpleasant memories, so I do all I can to avoid the situation. If it's really a concern, get a steering damper and you'll greatly reduce your odds of serious headshake in the future.

EvilSteve said:

I know this is really picky but a steering damper doesn't stop headshake. It hides it. Your bike is still unstable in those circumstances, just the steering damper stops the bike expressing this instability in a violent manner.

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I hate when people start debating this. EvilSteve is right. The damper will mask the real issue which is the stock geometry and suspension of the monster...period. There should be no debate on this. A damper MIGHT save you from crashing but the monster is just not set up for real aggressive cornering in stock form. You need to get more weight over the front of the bike. To do this, The rear needs to be raised and I would recommend clipons. Also, set the suspension up for your weight. I race a monster along with several others (ten total locally), and NONE of them use dampers. We don't because we have all set up our bikes for track use, not cruising around town and moderately cornering which is what the monster is set up for in stock form.
In general, just bolting on an accessory to solve problems is a very bad idea. I try to ignore these posts because I get tired of hearing all the bad advice but sometimes I can't just ignore it.
There are some reasons to use a damper on a monster but not for just aggressive cornering. If you wheelie alot or get the front end light coming out of corners, you need one. Or if you are riding bumpy corners, you need one. You see it is designed to reduce the shake that occurs when the front end gets light, or off the ground then gets back down at an angle (not in a linear direction with the bike)
So, to sum it up, damper will reduce the shake and MIGHT save you from a crash. However, If you are getting it to fix the unstableness from cornering, I would fix the problem instead of trying to put on a magic band-aid.

fasterblkduc said:

I hate when people start debating this. EvilSteve is right. The damper will mask the real issue which is the stock geometry and suspension of the monster...period. There should be no debate on this. A damper MIGHT save you from crashing but the monster is just not set up for real aggressive cornering in stock form. You need to get more weight over the front of the bike. To do this, The rear needs to be raised and I would recommend clipons. Also, set the suspension up for your weight. I race a monster along with several others (ten total locally), and NONE of them use dampers. We don't because we have all set up our bikes for track use, not cruising around town and moderately cornering which is what the monster is set up for in stock form.
In general, just bolting on an accessory to solve problems is a very bad idea. I try to ignore these posts because I get tired of hearing all the bad advice but sometimes I can't just ignore it.
There are some reasons to use a damper on a monster but not for just aggressive cornering. If you wheelie alot or get the front end light coming out of corners, you need one. Or if you are riding bumpy corners, you need one. You see it is designed to reduce the shake that occurs when the front end gets light, or off the ground then gets back down at an angle (not in a linear direction with the bike)
So, to sum it up, damper will reduce the shake and MIGHT save you from a crash. However, If you are getting it to fix the unstableness from cornering, I would fix the problem instead of trying to put on a magic band-aid.

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You just listed several valid reasons why a damper might be needed. So, not everyone looking to put a damper on their bike is trying to mask a problem or doing something wrong. Even on a superbike with clipons and a heavy in-line 4 cylinder hanging over the front wheel, the front end can still get light and get some headshake. The professional riders who reviewed the new ZX10 criticized it for its lack of a damper and its tendency to headshake.

You are 100% correct that getting more weight over the front will help reduce most headshake, but it may not eliminate it for the reasons you stated. My bike lifts the front in 3rd while laying on the tank and I have raised the rear spring too.

Also, not all riders will be riding in attack position all of the time. On the track you will keep your weight forward and ride aggressively. But, on the street you may be more laid back. You are also more likely to encounter rough pavement and unexpected situations that may cause you to make unplanned maneuvers.

So, I look at it this way. If a bike is more prone to headshake due to a high power to weigh ratio, a short wheelbase, a steep rake, or a high rear weight bias, the more it needs a damper. It is not necessarily masking a problem. My old R1 would headshake under the right conditions, but my Warrior would never, due to the long wheelbase and rake. I would not say my R1 had poor geometry or suspension compared to my Warrior.

Again, I agree with your technical points. Some bike geomtries are more prone to headshake. I just don't see them as wrong. There is always a better chassis.

Finally, if it saves your butt, it is worth it.

I'll pile on. You can have a very well sorted bike and still get head shake over certain road/track irregularities. You shouldn't necessarily get tank slappers, but enough head shake to make you want to do something about it. Head shake is simply your bike's inability to damp violent forces acting on it and transfer them back to the ground.

My last track day bike was a very well sorted F4 (Computrak, Fox, Lindemann) and I had to add a damper specifically for the bumps going up the hill at Laguna between 5 and 6 (as well as certain roads I rode on weekends). When you're on the gas and your front end gets light and you hit a series of sharp bumps, you're gonna get head shake on a sport bike. I would get it every time up that hill. Added a rotary damper and it was totally eliminated. I could power right through there.

The idea that you shouldn't add a damper because it's not solving the root problem is misguided. A damper is nothing more than a shock absorber that's there to respond in situations where a force is too violent for the suspension of the bike to dissipate/rebound back to the ground. It is essentially like having a second stage suspension device to respond at the extreme end of the spectrum, because there is no way to set up a suspension to do that and still be compliant in normal riding situations. Dampers are an integral part of any sport bike set up and riding hard without one is really being penny wise and pound foolish. Note their presence as standard equipment on some of the new sportbikes.

Now if you're getting tank slappers in every day riding situations, you've got a serious suspension set up problem. One common cause is putting sticky tires on a bike with too much flex in the frame or suspension. I'm not gonna think about putting stickies on my S2R until I get my suspension sorted out. I think it's just asking for trouble.

Just my $.02. YMMV.

Well, I just came in from a nice ride except for the last 5 minutes when my S4RS went into a terrible tank slapper while I was going at a moderate speed into a moderate corner. I didn't accelerate out of it; rather, I let off the throttle and applied the brakes. Maybe this wasn't the text book solution to the problem - but it all happened pretty fast and this saved my ass. Needless to say, this was a pretty scary event and makes me unsure about riding the bike going forward.

Now here's the thing - I have an Ohlins adjustable steering damper on the bike. It was cranked all the way to the stiffest setting. The fact that I still had a pretty violent head shake in what I consider to be a routine corner and at a "slow" speed (approximately 60-70 mph) is more than unsettling to me. I can't believe that Ducati (or any manufacturer) would design a bike that would do this. The bike came out of the box with nearly every top of the line component, which is why I wanted it. Then I rode it and noticed how squirrelly it was. Relative to my R6 it felt REALLY unstable at higher speeds and in corners (the Monster "wobble"). I didn't like the way the bike handled, so I added the damper. And to no avail.

I just had the scariest experience I've ever had on a bike. My S4RS is real pretty, but I don't think I want to ride it anymore. I just don't want to be on a bike that I know has a tendency to do this type of thing. The riding position, power, and light front end all add up to a very uncertain experience.