Increased rake modification + steering dampener, a possibility? Any reason?

[Erin_S]

Hello,

I'd read that the newest bikes have steering dampners because of the more "extreme" suspension geometry that they're working with.

So I thought, what if I did the same to my bike? I could in theory, lower the front about 1-1.4" (before contact with the shock) and raise the rear about 2", for 3-3.4" of difference total. This would give me a much improved rake, but should be unstable. At this point a steering stabalizer should be required.

So with a more extreme setup + stabilizer, would there be any benifit? Would it work out?

Thank you!

[Alex]

I don't think there is any benefit. None of the 1st-gen ninjettes (or 2nd-gen, to my knowledge) set up for trackday or even club races use steering dampers. According to some posts on the ninja250.org board, the only exception is WERA where there is a rule that all bikes require dampers, so the ninjette folks evidently put on old GSX-R ones and dial them down to no resistance. If the trackday folks don't need it, anyone not taking it to the track most certainly doesn't need it. If the geometry is changed to something so radical to cause the bike to be prone to tankslappers, it's already so far out of the acceptable settings for the frame and every other component on the bike that it would not be any faster around a track or even feel better on the street.

Here's a related thread on the ninja250.org 1st-gen site.

[VeX]

Wow that's extreme! The term that's used is 'trail' the more you decrease trail
the faster the bike steers, but the less stable it can become. Trail is measured if you draw an imaginary line from the fork tube bottom to where it'd touch the pavement. Then if you draw a line straight down from the axle and measure the distance between the two lines...

Doing a total lift/raise like that for a 3" difference is very very drastic! Steering dampeners are NOT meant for fixing headshake issues and I get the feeling if you did that the bike would be a mess on the freeway. Steering dampeners are meant for acting as a kind of shock for the steering system to smooth steering movements. If you get a tank slapper the steering dampener isn't going to fix that.

Hell I was considering moving my back DOWN about 1/2" and a little more on the front end to offset the 5/8" I already did!


Edit: I found a picture (albeit of a bicycle)

[Alex]

Originally Posted by VeX

Steering dampeners are meant for acting as a kind of shock for the steering system to smooth steering movements. If you get a tank slapper the steering dampener isn't going to fix that.

I'm not sure I fully agree with this. A well-sorted suspension should not be prone to tank slappers, with or without a dampener. I think we're agreed there. But a steering dampener (I always switch back and forth between damper and dampener, forgetting which is correct) can most definitely keep a bike from going into a tank slapper, at a cost of steering feel, steering quickness, and comfort. It's a bandaid, and if it is being considered because everything else is hosed up, then that's the wrong solution. But it does provide a margin of safety that does allow supersport machines to run with a steeper head angle and less trail than they would be able to otherwise.

[Erin_S]

Alright, then the suspension article I read was a bit incorrect. Thanks for the information.

BTW on kawiforums, I did see a track guy getting a stabilizer... not really sure why in this case.

[Alex]

Makes sense. There's certanly nothing that prevents someone from finding a way to mount a dampener on a ninjette, it's just that I wouldn't expect there to be any real benefits.

FWIW I do feel more comfortable with one on my 10R. The magazines pummeled the 1st-gen 10R when it was released without a steering dampener, and the geometry was so severe and the power on that bike hit so hard that it really was prone to the wiggles and even slappers on uneven pavement when accelerating hard. So Kawi put a one on the 2nd-gen 10R's. The one they put on is quite light, even at full stiff you can still move the bars pretty easily, but it does make a noticeable difference on the track. When the front end skims the surface or leaves the surface for a short while when accelerating, it gets a little wiggle. At each track, I dial it stiffer and stiffer until the wiggle pretty much goes away, then dial it back a notch or two. If it is set so stiff to damp out any wiggles, it's set too stiff for quick handling and steering feel in tighter turns.

[Erin_S]

So, mind if I ask why you don't just raise the front or lower the rear of the 10r instead of having the dampner? Wouldn't that give you the "well sorted suspension instead of a bandaid" that you've been talking about?

[Alex]

Doesn't work that way. The 10R is built for braking at the end of a front straight from 180 mph, and accelerating with 165 hp at the rear wheel, and has a frame design and suspension components to match. Suspension height in front and back (and its suspension design in general) is a compromise to allow it to do both of those, while still being both compliant enough to maintain traction, yet stiff enough to provide proper feedback in turns. At the end of that design process, the front end is twitchy enough that a steering dampener provides some real safety on the track. That's not unique to the 10R, all 4 japanese liter-bikes (as well as pretty much all big-bore sportbikes from any other country) run standard dampeners now, and even most of the supersport 600's are currently coming with them. None of that means that adding a dampener is the right solution for a ninjette. Heck, even for those bikes the latest rage for the dampeners is to have them flow almost freely up to triple-digit speeds, then add damping as the speeds get north of there. That's the current tuning on the HESD dampers (electronically controlled steering dampeners) on Honda's 600RR and 1000RR, and is suspected on the R1.

Tipping a single-steel-tubed frame bike on its nose (like our ninjettes) will not magically transform it and make it handle like a supersport bike. The front forks aren't designed for it, the steering head isn't designed for it, and the frame itself isn't designed for it. Making small ride height changes may help some feel, but not even close to the point where a dampener would be necessary. The good news is that the ninjette doesn't have to be set up to handle like a supersport bike; it sees no time (ok, very little time) in triple-digit speeds, and its advantage on the track as well as on the street is its incredibly light handling and ease of changing direction.

If you'd like to find way more info about this than is available yet on this site, I'd point you to Tony Foale's book on motorcycle chassis design. Smart guy, good writer, and excerpts from the book have made for some darned good articles over the past few years. He's up at:

http://www.tonyfoale.com/

and has his book for sale right on that site.

[Erin_S]

Thank you sir. I've been trying to apply what I know of car suspensions to cars, and coming up decidedly short in some areas. Thanks for the in depth explanation! ^_^

[Sailariel]

Erin, I build bicycles. Two millimeters in rake can make a difference between a twitchey, unstable bike and one that steers intuitively like the Ninjette. It`s all in the geometry.

[Erin_S]

Why take a chance?

What chance? I can lower a proven amount and remain safe with benefits. Why? Because it will give me what I want.

Suspension design might be different for motorcycles, but the ideas are the same. Stock is fine for some people. Modifying... you either run a risk or research intelligently first.

That's what I do. If it's "why lower your front end" or if it's "why do that to a working motorcycle (my project)" it's because I'm getting what I want out of it. If I screw something up, that's on me... But I'll bet on my brains against what if any day of the week, and if I lose, no one loses but me.

[Cling]

Steering Dampers will prevent tank slappers, who got in their mind that they wouldnt???

If you harden up a piston style steering damper and pull the rod back and forth through it, it will move back and fourth fluently and surely depending how hard or soft you have it set(considering that it is operational and the oil is still good). But, if you hit the piston of that same damper with say, a hammer, or your hand really hard.... the piston will not just slap to the other side because you hit it so hard this time, it will stop abruptly due to the not-so-fluent push.

Now consider this when thinking about a tank slapper, during a tank slapper the handle bars on your bike will be slapping back and forth faster then you can imagine or help. So the more intense the slapper, the quicker a damper will stop it...

I've had my fair share of slappers on the track on my first bike (600rr) and i'll tell you that since I installed my first damper, i'll never ride without one again. Its 400$ of insurance that could save your life.

[Erin_S]

So on a dampner, it seems that the mechanism for the dampning function is movement vs compression of a sealed gas/liquid of some kind, is that right? Do you have a dampner on a street 250? Any thoughts on street vs track needs? Did you do it with stock geometry or have you decreased rake?

Edit:

Seems like they're just a normal shock with low speed dampning turned way down and high speed turned way up...

[Alex]

Originally Posted by Erin_S

Modifying... you either run a risk or research intelligently first.

That's what I do. If it's "why lower your front end" or if it's "why do that to a working motorcycle (my project)" it's because I'm getting what I want out of it. If I screw something up, that's on me... But I'll bet on my brains against what if any day of the week, and if I lose, no one loses but me.

Erin -

You're getting some pushback, from me at least, because bikes <> cars, and experience with one doesn't directly translate to experience with the other. It's nothing personal, but you simply can't make any intelligent decisions about major suspension or chassis changes at your current level of riding experience. If you don't know what a nice-handling motorcycle is supposed to feel like as it nears its limits, you simply can't make determinations about how to improve it, no matter how much you read and try to learn online.

Nothing wrong with wrenching. But there's nothing wrong with riding, either, and until you get enough seat time to truly understand what the motorcycle is doing underneath you and how it's supposed to behave, changes for the sake of changes are as likely to hurt handling as they are to help. If I were you, I'd try and put on 5K or even 10K miles on your bike before even considering the types of geometry changes you're posting up about. (The remaining issue is that those with 100's of thousands of miles on these bikes and who modify them for their fastest performance on a road-race track don't see benefit in such changes, but that's a different issue)

I don't mean this to be confrontational at all, and certainly don't mean to discourage any of the neat things you want to do with your bike. I'm really enjoying your build thread. I'm primarily basing this on your posts about this being your first bike, you haven't taken MSF, and you're learning the sport on your own by riding alone. Those three items worry me a bit, and I hope you get over the hump of learning this crazy sport without any negative consequences. If it turns out I've misread your posts and you actually do have years of experience on bikes, and have been wringing the heck out of them for tens of thousands of miles, please forgive me and that would certainly change some of these things in my mind. Good luck...

[Cling]

Originally Posted by Erin_S

So on a dampner, it seems that the mechanism for the dampning function is movement vs compression of a sealed gas/liquid of some kind, is that right? Do you have a dampner on a street 250? Any thoughts on street vs track needs? Did you do it with stock geometry or have you decreased rake?

Correct, and I have had the ultimate experience with dampers, I had an 05 ZX10R and ran Dunlop 209's on it, 209's themselves promote massive head shake in most bikes because of their extreme track oriented profiles, combine that with the extreme head shake that the 04-05 ZX10R's come with stock and you got a bucking bronco on the track. I ran a Scotts damper on my ZX10R and never even had a close call with tank slapper, sure I 'started' them a lot coming out of turns and running full throttle down the straits, but they NEVER continued on to a full tank slapper.

Dampers will help prevent tank slappers on any bike, period.

[Erin_S]

Alex:

Totally in agreement about the experience thing. If I were basing what I do from experience... well. It wouldn't be good. : /

But I'm an engineer first. Physics are physics... no matter where you go or what you're doing. I'm not saying that experience on a car equals that of a bike, I'm just talking about an understanding of mechanics. Sorry about the misundertanding there.

I see flaws, I need to fix them... I could make an argument about how I'll be ok, but it wouldn't really mean anything... just a newbie defending why she got a supersport for a first bike... same thing. I don't need to ride the bike any more to know that the rake is kind of high and that there's too little weight on the front end. I need to replace my bent handlebars anyway, because of previous owner accidents (bent slightly on both sides, had a coupld road racers check over my bike for weaknesses one day). In fact, the geometry of my bike is actually already altered by a total of .63" of lean towards the front (the front forks were fully raised into the handlebars and the tires on it are 130/90 and 100/90). In order to keep that, I'll need to lower the front an additional half inch anyway when I get my new MT75's this week.

So in short, I'll be careful. If things start getting twitchy, I'll just pull it back. I should be completely safe based on the research I've done.

Thank you for the concern though, your heart is in the right place, Alex.

[Alex]

Damn engineers, convinced they know best and always mucking with stuff! (spoken as a damn engineer, who's convinced he knows best, and is married to yet another, who's equally convinced she knows best)

[Alex]

Originally Posted by Some funny guy elsewhere

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[Dan Kyle]

Originally Posted by Erin_S

Hello,

I'd read that the newest bikes have steering dampners because of the more "extreme" suspension geometry that they're working with.

!

What you are talking is Geometry, suspension is tied into geometry, but the two are adjusted separately.

It is best to have a reason to change geometry BEFORE changing it rather than just experimenting without an objective.

For example:
Do you want the bike to turn in with less effort (faster)?

Does the bike not "finish" the turn correctly. (under acceleration it pushes to the outside of the turn)

Both of these are adjusted with Geometry, but before adjusting you want the suspension springs to be correct and the sag to be correct, or you will be chasing your tail forever.

As pointed out by "Alex Allmayer Beck" Very small changes can have very large effects.

Here is some basic Geometry info.
Geometry Basics
Ahhh, geometry is complicated.
So many things have a direct effect.

Basics:
As stated by others already as the rear of the bike is raised you lose trail.
As you raise the front of the bike you gain trail.

Trail is the built in stability of the bike.
You want as little trail as possible, but you MUST have enought to insure both stability and the ability to STEER.

As you remove trail the bike no longer want to go straight, it wants to fall over or turn.
This is what happens entering a turn, the less trail the lighter and faster you can change direction.
But as you exit the turn, you are already leaned over and now are applying power.

Now you need to be able to hold your line, tighten your line or loosen your line, I call this the ability to STEER.
The two, turning and steering, are different.
If you do not have enought trail, as you exit a turn and apply power, your bike will push to the outside and the only way to stop it is to back off the throttle.

Other things that effect turning and steering, tire shape and construction. Weight and where the weight on the bike is.
Wheelbase lenght.
Handlebar lenght and angle (leverage).
Footpeg lenght and location (leverage).
Suspension.
Gearing, especially on a 1098 as you change ride height as you adjust the chain tension.

Just some notes:
As pointed out already when you change the Triple Tree offset, (the Ohlins guys hate when I say that they call them Triple Clamps), from say 36MM to 30 MM you are increasing trail, adding stability, making it harder to "turn in". But you are also reducing the wheelbase by that same 6MM, that is a lot!! On conventional swingarms you can usually add some wheelbase lenght back in, but iot is not so easy on a single eccentric single sided swingarm.

More stuff: all these numbers are appox.

a 1 degree RAKE change is about a 6MM change in trail

a 4MM rear ride height change (measured at the rear axle) is about a 1 MM trail change

a 4MM front ride height change is about a 1 MM trail change.

a 1mm offset change is a 1mm trail change and a 1mm wheelbase change.

[CRXTrek]

Thanks for this Info.

You confirmed my thoughts on why my bike changed so much with my clipons.
Leverage and more weight on the front.

[randomwalk101]

Scotts (made by Ohlins) is a rotary type, more compact and less prone to break in a crash. It's very good unit (do a google search and see the reviews).

They do make one for the 250r now. here is a link to the 08 or 09 model. They have one for earlier years too...just use that link and navigate to find your bike/year.

http://www.scottsperformance.com/Sta...dd_On=%20Ninja

if we are interested, should get together and organize a GB for much better discount of retail. I must warn you, it's not cheap though..but like anything in life, good sh*t doesn't come cheap.

[fjyang]

2-3" change in ride height in either direction are vary drastic that will not be compensated by steering dampers alone. A lower profile tire there and a 1/4"-1/2" max change in rear shock length will change a bikes handling more then the numbers suggest.

If you like to play around with ride height (geometry) of a bike, have you thought about adjustable linkages for your rear shock so you can "experiment" 1/4" at a time without putting yourself in harms way.