steering dampner mod

[rubber2burn]

I'm not trying to tell anyone how to set their bike up, just a note of wisdom from my experience.

I know I can speak for a lot of people when I say that I appreciate you sharing your thoughts.  

+1 on that I put 90W in mine but after seeing this post I might Drop it down a little to a lighter weight oil. I have had no problem with the 90W that is in there now but then again I am not riding to the full potential of the bike maybe only using 60%

 

[dewie]

Yeah, I'm not a pro rider and I live 3 hours from real good corners. 10w30 might be the way to go for me. I just seen all these write up on 80/90 and never thought of even using 30w..

 

[micbusathens]

I believe a 20w to 30w fork oil will be perfect.Only this type of oil contains antifriction additives and allows rod not to stick to the oil seals

 

[Mr Bogus]

15/40 synthetic for mine

 

[IG.]

I filled it with a syringe while the rod is as much out as possible. Then put the screw back, plunge it a few times. Repeat the process a few times till you are positive it's completely filled.

On the subject of oil weight, I put 80w gear oil and I think it's better than 30w. First, I tested that low temperature is not critical. I put the damper in the freezer for a few hours, and even after that I could move it with my bare hands - resistance was noticeably more, but it moved OK. Note that when on the bike, you have a better leverage through handlebars, so even when riding in sub-freezing temperatures, I could not tell the damper makes it harder to turn the bike. Also notice, that at higher speeds, it is harder to turn the front wheel because of the other two forces (self straigtening force of the front wheel, and gyroscopic force of the front wheel), so the presence of the damper is not noticeable.

I went down because of a real tankslapper (not a headshake) and know the magnitude of forces during the tankslapper. The whole experience was like a giant shook you a few times and threw you off the bike. The stock oil I had did absolutely nothing to combat the real tankslapper! 30w is not much better. I've been riding with 80w year around for a couple of years now, pretty aggressively I might say, and I don't have handling problems, i.e. the damper with 80w does not impair my normal riding.

Here is the thread where I posted a lot more detailed explanation of a tankslapper dynamics, what causes it, and how to minimize the chances of a tankslapper.

https://www.hayabusa.org/forums/?act=ST;f=6;t=84892;st=25

For the lazy ones, here is a copy of my post from that thread.

I had a genuine tankslapper at about 110 in the wet on the banking of the Pocono Raceway (out in PA) while crossing the bump. It was like a giant shook me and threw me off the bike. I slid on the wet pavement, rolled a few times and stopped about 5 ft from the wall. I walked. The bike was a bit banged up as it slid on its left side, and hit the wall with the top of the bike. I did a lot of thinking, and as I read through the posts I see some valid points and some misconceptions on the reasons why tankslappers happen, and how to prevent them. Here are my thoughts on this.

Why do tankslappers happen? The bike's forks (and any car's front wheel shocks for that matter) are at an angle which we all know about. The angled forks move the contact patch of the front wheel slightly behind it. As a result, the entire momentum of the bike moving forward and the ground moving in the opposite direction create the force which wants to keep the front wheel straight. Which is a good thing. It's mostly this force (and some of the gyroscopic force) which resists turning the front when you try to make a steering input. It's the same force which straightens the front wheel if left alone. Let's call it the straightening force.

During normal riding when the front wheel is never too far off the alignment, this straightening force is very useful. However, the amount of this straightening force grows dramatically when the front gets more than 5 deg out of alignment. Setting down a wheelie with a croocket front wheel is a typical example when this might happen. This however is an easily fixable example - just land with the front mostly straight.

There is a bigger problem because it may happen during seemingly normal riding. Believe it or not, but in order to stay in turn, we have to constantly apply steering input (pushing the inside bar, or pulling the outside bar) - whether you realize it or not (ask me for proof if you don't believe it, I don't want to crowd already lengthy explanation). So, when the bike stays in turn, the force of your steering input is balanced with the straightening force of the front wheel. When/if the front gets light even for a fraction of a second (a bump, wet, light front on acceleration out of a turn), the straightening force of the front wheel is greatly reduced for that fraction of a second. But your steering input (which tries to turn the front wheel to the outside of the turn) stays the same. As a result - the two forces which were in balance, but now are not - the front gets croocked (turned a little too far to the outside of the turn), and when the next moment you passed the bump, the front is no longer as light as the moment before, and the straightening force (which is far greater because the front wheel is turned to the side more) is trying to straighten the front wheel back into alignment. That's the start of a tankslapper.

The only thing that can truly slow down the swing of the front wheel is your steering damper - not your hands, not the throttle which has been ripped from you hands.

Let's pause for a moment and think. What can we do? First, let's think. The tankslapper happened because the front got out of alignment too far. And it got out of alignment too far because our steering input pushed it there when the straightening force of the front wheel disappeared for a moment when the front got light. OK, so if we could somehow reduce the amount of steering input we need to apply to go through the turn, that would help, right? OK, we could reduce the amount of steering input to keep the bike going through the turn by... moving our upper body to the inside of the turn! Don't even bother to hang off if you don't want to. Just move your upper body to the inside. You would be able to take the same turn with the same speed, but with less lean and with less steering input required to stay in turn.

As a side point here is that tensing on the bars creates unwanted steering input which can only contribute to the problem, and relaxed grip minimizes it.

But, what if you already got into the tankslapper? Frankly, there is nothing you can do. The fact that you got into it indicates that the oscillations are increasing and not subsiding. That's where a steering damper is the only thing that can introduce enough resistance to make the oscillation to subside. That's why it is so important to either replace the stock oil in the damper with 80W gear oil, or get the aftermarket damper. It's simple physics. A little more resistance and oscilations subside. A little less, and they increase.

Another thing is that this may not happen for years. When people say they installed a damper and immediately feel the difference, it just makes no sense. A little headshake on uneven surface is normal - it's the straightening force of the front wheel which works its way through uneven surface. The steering damper only matters if it saved you from a tankslapper. Otherwise, it's pretty useless.

So, to sum it up. Refill your damper with 80W, or upgrade it. Minimize steering input in turns by shifting your upper body to the inside, even before the turn. Staying relaxed minimizes your steering input to only what is necessary.

 

[Enginerd]

I got into a less violent one coming down off of a power wheelie one day and was told by a good friend that IF you don't get the throttle taken out of your hand, the best thing to do is it give it a handful and lighten the front end up and bring it back down slowly if the riding conditions permit... I did just that and actually ended up picking the front tire up a little again and came down a little straighter I guess and it stopped instantly. Just a bandaid but def thought it would be worth saying. Could have saved me from hitting the curb of the jersey wall hard. How hard is it to get to the steering damper? Can I do this without removing the nose... Heavy, might have you help me with your suringe method once it gets nicer out

 

[heavybusa]

Thanks for the post IG

 

[Tufbusa]

Well IG, you certainly have expressed in great detail your opinion on what creates a tank slapper. Obviously, after a real life experience with a genuine slapper, you have a great understanding of the violence involved.

While I agree with many of your points of origin, I highly disagree with your empliment of cure.

With your test of the dampers function filled with 80W oil and how it slowed the cycle with a simple push pull hand test, leaves no doubt the damper slows the steering. With such a personal experience with a tank slapper and how violent it becomes, I should think it would be necessary to do a test on high speed cycles of the 80W damper as well. I think you'll find with 80W oil, the damper will totally fail at high speed?

It is possible, there is a reason why the only dampers filled with 80W oil was created in someone's garage?

Also, I would think a test of both high and low speed dampening with a lighter oil such as 30W or 40W should be completed before recommending any particular weight oil?

Remember, your dampers job is to slow down the ocillation, not stop it.

I agree with you, the best application is an adjustable damper. Even more important is to learn how to use it!

 

[dewie]

damn you both, I'm confused as hell now!!
Just joking, both you guys are making great points. Now who wants to "donate" their bike and a$$ for tank slapper research?

 

[BrianK]

i have 75/90 synthetic in mine and it is fine. steering is not to heavy. stock fluid in there is to light

 

[heavybusa]

damn you both, I'm confused as hell now!!
Just joking, both you guys are making great points. Now who wants to "donate" their bike and a$$ for tank slapper research?

 

[Tufbusa]

damn you both, I'm confused as hell now!!
Just joking, both you guys are making great points. Now who wants to "donate" their bike and a$$ for tank slapper research?

Dude, I have crashed so many times, I've actually invented ways to crash and it was no more fun the last time than it was the first time

In 2003 I scattered a brand new busa into so many pieces we hauled it home in boxes as a direct result of a tank slapper from hell which was generated by applying the rear brake ever so slightly at a very inopertune time.

But if the price was right, I'm sure I could take YOUR busa and put her into a tank slapper with very little effort and you could even ride on the back

 

[Aquaman]

Crashing is one reason for becoming a much better rider.

 

[dewie]

But if the price was right, I'm sure I could take YOUR busa and put her into a tank slapper with very little effort and you could even ride on the back    

sweet, where do I sign.
I've been in a lil tank slapper on a bike with no damper and I'm amazed I kept it up. I have no desire to ever do that again. So I can donate my bike for the protection of my fellow busa brothers and sisters.

 

[IG.]

Tufbusa,

I clearly indicated that riding with 80w oil in the damper I cannot tell the difference. This includes track days and a very aggressive street riding. The 80W oil absolutely does not stop the steering.

What you possibly imply is that 80w is so thick that if I let's say land a wheelie with a cocked wheel not only my damper would slow down the oscilations enough, it would actuall stop it. You have a small point here in a sense that I cannot actually test my setup, short of creating a tankslapper on purpose.

However, consider this. I put my bike on a stand so that the front wheel was off the ground. Then I moved the handlebars left and right as fast as I could. I felt some resistance but nothing to the magnitude like my handlebars would stop.

So, my gut feeling after all this experimentation is that if anything, the poorman's steering damper (aka stock damper filled with 80W gear oil) may not have even as much stopping power as a good quality damper at high rate of oscillations. But, I wouldn't be concerned for it to be stiffer than a good damper at high rate of oscillations. At the least, it is much better than the stock, and maybe somewhat closer to a stopping power that a quality damper provides.

BTW, the 80W mod has been around for a while, and it would be interesting to find someone who had a tankslapper with 80W. Now that I think of it, I don't remember a single post saying that someone with 80W oil got into a tankslapper. I can draw only one conclusion from this - the 80W mod actually works. You are on, bro! LOL

 

[Mr Bogus]

if you got the cajones... just let go of the bars... I had a Triumph that I could get to wheelie and when it came down, you could almost promise a good tank slapper.. I tried to ride it out but only made it worse... If I let go of the bars, it would quit.. Just the frequency of the oscillation I guess but sure is an eye opener

 

[pbghost]

I used straight 60w, no problems, although it's pretty stiff below 35f and it tight parkinglot maneuvers. handles great on the rough neglected roads we have here( compared to stock oil) and never had the fortune of having a tank slapper, nor do I want too.

 

[BrianK]

Tufbusa,

I clearly indicated that riding with 80w oil in the damper I cannot tell the difference. This includes track days and a very aggressive street riding. The 80W oil absolutely does not stop the steering.

What you possibly imply is that 80w is so thick that if I let's say land a wheelie with a cocked wheel not only my damper would slow down the oscilations enough, it would actuall stop it. You have a small point here in a sense that I cannot actually test my setup, short of creating a tankslapper on purpose.

However, consider this. I put my bike on a stand so that the front wheel was off the ground. Then I moved the handlebars left and right as fast as I could. I felt some resistance but nothing to the magnitude like my handlebars would stop.

So, my gut feeling after all this experimentation is that if anything, the poorman's steering damper (aka stock damper filled with 80W gear oil) may not have even as much stopping power as a good quality damper at high rate of oscillations. But, I wouldn't be concerned for it to be stiffer than a good damper at high rate of oscillations. At the least, it is much better than the stock, and maybe somewhat closer to a stopping power that a quality damper provides.

BTW, the 80W mod has been around for a while, and it would be interesting to find someone who had a tankslapper with 80W. Now that I think of it, I don't remember a single post saying that someone with 80W oil got into a tankslapper. I can draw only one conclusion from this - the 80W mod actually works. You are on, bro! LOL

 

[Nekosohana]

Hmmm, good or bad, I did the damper mod with Lucas 90w oil and I like it. I like the firmer feeling it offers.

 

[Revolution]

you have to WORK the bubbles out [.]

when i first did this mod i used 30w oil. there was hardly any difference from stock. i changed it to 40w and the bike feels solid, and the steering does not feel heavy in parking lots.