954 head shake - Wrist Twisters
 
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post #1 of 13 Old 06-20-2008, 03:57 PM Thread Starter
 
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954 head shake

Exiting a corner on my new 954 this afternoon and hit some ripples in the pavement. I've been riding a long time and the front end started shaking back and forth like I've never experienced - almost dumped it. I've read about this but I didn't think it would be so severe.

Anybody have a steering damper thay would like to sell? If not, what unit would you guys recommend. I don't plan any track work with it but based upon this experience, it seems to me that this bike needs one even for mild street riding.

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post #2 of 13 Old 06-20-2008, 04:09 PM
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I used Scotts on my track bikes.

I put a daytona damper on my R1 and fro street duty it was fine.

Cheap and adjustable.

It cured all my my headshake issues on the R1 for street riding and my confidence on that bike more than tripled once the damper was installed.

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post #3 of 13 Old 06-20-2008, 04:47 PM
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I'm a big fan of Ohlins. Before you go off on a tangent be sure the front end and tire are not the culprit. Pay particular attention for loose steering head bearings.

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post #4 of 13 Old 06-20-2008, 05:04 PM
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Geez, a 954 without a dampner... that's a scary thought. Get a Scotts on there asap.

'02 RC-51
'10 Unicycle

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post #5 of 13 Old 06-20-2008, 05:30 PM
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Quote:
Originally Posted by ragdoll View Post
Geez, a 954 without a dampner... that's a scary thought. Get a Scotts on there asap.
The 954 has a 17" front wheel. It is the older models with the 16" wheels that were scary.

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post #6 of 13 Old 06-22-2008, 04:45 AM
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My 929, basically the same bike, has 37.5k on it and has never had a tankslapper. No dampner. Lots of times the front tire was barely skimming the earth coming out of a corner. But I always changed front tires before thay got too worn.

The cure for tankslappers is supposed to be a steering dampner. But I've never heard what for sure causes them. Some guys get them. Others don't. A lot of guys bought expensive dampners that never experenced a tankslapper just to be on the safe side. Me? I'm cheap, and I trust Honda. I won't spend several hunderd $$$ unless I'm sure I need to.

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post #7 of 13 Old 06-22-2008, 06:53 AM
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Sniper... I have no numbers to back up my experience... but here it is...

The 929 IMO is a far more docile bike that the 954. The 929 was very capable for everything I wanted it to do and gave me tons of street confidence. I felt as if I could ride the 929 all day at whatever pace I felt like.

The 954 felt much more razors edge to me. Very similar to my R1 with regards to stability (that is not a compliment). The front always wanted to walk. It required you to run wider that you wanted to ride around a headshake. The 954 required more attention to what I was doing do to its seemig desire to "twitch."

I almost liken it to comparing the F4i to the 600RR. For a dedicated track bike the RR will win. For a bike that is usable in almost all conditions, I will take the F4i.

The rr needed a damper to ride hard; the f4i did not.

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post #8 of 13 Old 06-22-2008, 05:21 PM
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Woohoo, I love talking about head shake!!!

Dampers are not cures, but band aids. You can setup a street bike to be stable enough that a damper is not required IMHO. I ride what is supposed to be the most "race oriented" middleweight (2007 R6) and I have not had any significant head shake. I also run much lower pressure though, 32 PSI in the front as opposed to the 36 PSI they suggest. This probably reduced head shake as it reduced the sensitivity of the front (but adds contact patch). If I do a trackday or start racing this thing I will get a damper for sure.

Have you checked your tire pressure? Remember that even a 2 PSI differential front to rear, ie 36/36 vs 34/36 can significantly change your geometry. A quick ghetto fix would be to run the rear 1 or 2 PSI lower than your front.

What SAG are you running? I would not recommend running racing SAG numbers on the street. The extra SAG and resulting suspension travel keeps that front wheel on the road as opposed to skipping over it. I think 35mm is a good starting point for the front and maybe 30mm in the rear. Too much sag in the rear is bad though, like not enough in the front.

Thoughts from racing:
You know you had a real bad tank slapper when you have no front brakes. I always pump my front brakes a little after a good slapper, something I learned when I grabbed the brakes at 155 and the lever went to the bar. Not cool.

You have to find the compromise between stability and turn in/steering effort. The problem is that the motorcycle reacts differently depending on what you are doing with the gas, brakes, weight etc etc. I try to set the bike up so that I am running minimum damper, but not too stable that I don't need the damper. At WSIR, if I didn't get a huge twitch into T4, I knew I went too stable.

Suspension setup and tires (profiles vs rubber vs construction) can cause head shake all by themselves. The rider can cause headshake too, manhandling the bars or even front/aft position.

Suspension affects loading of the tires. On the gas you can make it worse by softening the rear, making the front harder, reducing SAG in the front etc. Moto suspension setup is PFM as far as I'm concerned anyways.

I never needed a damper on my RC51 until I switched to Dunlop 208GPAs from Pirelli and Metzeler race rubber. I never had headshake issues on my 2000 R6 until I switched to Dunlop 208/209GPA from Michelin PR2/PR5s.

The issue with the Dunlops rears was that they grew with speed, so on the front straight and back straight the bike was getting more unstable. Dunlop suggested that taking out rear compression would stop the back from pushing the front and it helped a lot. The easy fix would have been to go back to Michelin...

Also, I was taught that using the kungfu grip on the bars can add to the shakes because instead of adding damping, you add to the energy. A trick was to modulate my fingers on the bars, kinda like jazz hands, in those places where the bike was head shake prone... and it worked. Don't let off the gas abruptly either because you end up loading the front more.

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post #9 of 13 Old 06-22-2008, 06:56 PM
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Quote:
Originally Posted by RayRevolver View Post
If I do a trackday or start racing this thing I will get a damper for sure.

Also, I was taught that using the kungfu grip on the bars can add to the shakes because instead of adding damping, you add to the energy. A trick was to modulate my fingers on the bars, kinda like jazz hands, in those places where the bike was head shake prone... and it worked. Don't let off the gas abruptly either because you end up loading the front more.
A CCS racer I talk to periodically told me before my 1st trackday that if it tankslaps you probably need to loosten your grip.
I have an '06 R6 trackbike and have no need for a damper. But it's not a 954 either.

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post #10 of 13 Old 06-22-2008, 07:13 PM
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well.... 6 years of track experience and I will stand by my statements.

My R1 was night and day with a damper. The 02 had a silly rake and trail and my experience on the 954 was a similar feel. You can play tire pressures to fix it, but I do not check my tire pressure before every ride. Nor do I want to mess with tire wear.
We can also talk about where you have your fork tubes in the triples etc...
We can also move on to talk about the street surface... etc...etc...etc...

We can talk about tires too! My RC handled much better on track tires than street tires. Its manner were much better.

Regardless of what you want to call it...

If you wait until you needed a damper to get one... you are in trouble.
There is a reason they come stock on some bikes.

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post #11 of 13 Old 06-22-2008, 07:15 PM
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Quote:
Originally Posted by gpzTurbo View Post
A CCS racer I talk to periodically told me before my 1st trackday that if it tankslaps you probably need to loosten your grip.
I have an '06 R6 trackbike and have no need for a damper. But it's not a 954 either.
As for this comment, it is true.

I have heard from several instructors at different times to cat as if your grips are eggs. Use your finger tips and gently handle the bike. You would be amazed at the difference. It almost seems you are creating most of your own handling issues if you "white knuckle" the bars.

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post #12 of 13 Old 06-23-2008, 03:55 PM
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Quote:
Originally Posted by hondaf4iguy View Post
well.... 6 years of track experience and I will stand by my statements.

Regardless of what you want to call it...

If you wait until you needed a damper to get one... you are in trouble.
There is a reason they come stock on some bikes.
I agreed with all of your points. I just feel that if the bike doesn't come with a damper, especially after the TL1000S fiasco, it probably doesn't need it for normal street pace. Rough roads with big throttle inputs can wreak havoc on any bike out there.

That said, I've had a major tank slapper with a damper too, and I was the only rider out of 4 that it happened too (6hr endurance race). Granted we were all different sizes, but with me on the bike it really required gentle inputs on the straights.

The big difference with a "tracked" street bike and a setup racer is geometry. It was a viscous cycle that as I sped up I needed more and more ground clearance. As the ride height went up, the bike became slower to respond.

The end result is running the rear even higher and head shake/instability comes along with it, so a damper is required.

I can see already that my current stock 07 R6 requires too much steering input mid-corner, so I am going to have to shim the rear (I don't want to buy an Ohlins just yet). With the shims and race rubber I am getting a damper just to be safe.

PS - these 06/07 R6s really seem to be sensitive to front/aft body position. I tended to ride the front wheel and it really made it feel like crap. I have been forcing myself further back in the seat on the entry/mid corner and it helps the feel a lot. I love stomp grip!

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post #13 of 13 Old 06-27-2008, 10:55 AM
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Never had a damper on either one of my F4i's, track or street. Never once did I come close to experiencing any type of head shakes/tank slappers. And I don't ride like a "girl" either, I rode the crap out of my F4i on the track and it handled just fine. Both F4i's had Racetek forks and suspension set up for me, tire pressure of course checked regularly and even more on the track bike.

As for whether I think bikes need dampers, 'maybe' the 600s can get away without having one but I think anything close to 1000cc should have one. I've lost 2 friends who both had 954's that died due to tank slappers.

And don't forget Marcus who had the RC51 that went into a WICKED tank slapper on the back straight at Mosport.

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