Cornering at high revs

[Doorag]

Since I'm still a fairly new rider I don't know if this is normal or not but I know that the collective wisdom of the mighty FZ6 forum can help me out.

As I have become more comfortable on the bike, I've been trying out riding in a lower gear at higher revs. A side effect I noticed the other night was how different the bike feels when turning over 8K. I thought there was something wrong with my bike, it turns so easily. Seriously, I thought the head race was loose or something until I did a few tests at the same speed ~55mph but at varying RPM levels.

At lower RPMs it's definitely slower to turn in and takes a lot more effort than it does at the same speed and higher revs. I assume the difference has something to do with the rotational weight of the cranks, etc... and that this is normal??

 

[Toympas]

Basically flip-ability is based on just one factor when the bike mo,tves: Unsprung weight.

Unsprang weight comes from the tires, wheels and breaking rotors. Also from the countershaft inside your engine.

The difference of unsprang weight versus total weight is that its factor "A" in the handling department.

The higher the spin of the wheel the heavier it gets. The heavier it gets, the difficult to flip from one side to another. It also help to ensure straight-flight as a counter-product (for example when you hit a bump in the road at high speed, it will continue straight).

The force that takes place here is the centrifungal (i think thats the correct word).

So the more the RPM's the higher the speed the faster you going. That adds to the unsprang weight due to centrifungal and your bike becomes stiffer at turning and handling.

Moto GP teams use exotic accessories to lower the unsprang weight, like carbon breaking rotors, magnesium-mate wheels, lighter tires. Also alot lighter counter-shafts (and in some cases placed horizontal instead of vertical to change the way the force is applied).

The Fz6 is in general a quite agile bike in comparisson to its bigger brother Fz1. What you are experiencing is the good effect of suspension.

When you twist the throttle and build up RPMs and you the corner, the rear suspension loads. The force keeps the suspension loaded in a lock-like type. When the suspension is loaded and specifically at 2/3s of its travel, the bike goes rock-stiff and its a great asset to your riding.

 

[Wolfman]

Basically flip-ability is based on just one factor when the bike mo,tves: Unsprung weight.

Unsprang weight comes from the tires, wheels and breaking rotors. Also from the countershaft inside your engine.

The difference of unsprang weight versus total weight is that its factor \"A\" in the handling department.

The higher the spin of the wheel the heavier it gets. The heavier it gets, the difficult to flip from one side to another. It also help to ensure straight-flight as a counter-product (for example when you hit a bump in the road at high speed, it will continue straight).

The force that takes place here is the centrifungal (i think thats the correct word).

So the more the RPM's the higher the speed the faster you going. That adds to the unsprang weight due to centrifungal and your bike becomes stiffer at turning and handling.

Moto GP teams use exotic accessories to lower the unsprang weight, like carbon breaking rotors, magnesium-mate wheels, lighter tires. Also alot lighter counter-shafts (and in some cases placed horizontal instead of vertical to change the way the force is applied).

The Fz6 is in general a quite agile bike in comparisson to its bigger brother Fz1. What you are experiencing is the good effect of suspension.

When you twist the throttle and build up RPMs and you the corner, the rear suspension loads. The force keeps the suspension loaded in a lock-like type. When the suspension is loaded and specifically at 2/3s of its travel, the bike goes rock-stiff and its a great asset to your riding.

Yes but if your rear suspension is too soft, and you give the bike a big wallop of throttle, it will make the suspension reach it's limits of compression pretty much straight away, and the rear of the bike will wallow out of a corner, and the only ways to fix this is one,stiffen your suspension so it doesnt get through it's stroke under acceleration, or two, apply less throttle less quickly. Soft suspension at the rear, if matched with a stiffer front end, will also have a tendancy to push the front of the bike, and make the bike want to sit up i a corner, and drive straight, rather than where you are pointing the bike.

 

[Kilbane83]

Look lean turn. Pick your line, set entrance speed, lean, and roll softly on the throttle until after the apex you can ping it pretty hard as you straighten up. Motorcycle suspensions are more stable the faster you go in a turn due to the suspension compression. G's press the bike into the ground basically flattening the tires and making the suspension compress and hold the ground.

The trick, especially on yamaha's it seems, is learning throttle control. Yammy's are known for touchy throttle response. Twist your wrist a bit to much and your rear tire is going to break contact and spin out on you for a nice lowside. Cut the throttle too hard (on our bike w/o slipper clutches anyway) midturn the suspension is goin to unsettle and you're going to get headshake making for a possible front end wash out or highside.

Higher speeds the bike likes to turn in easier, because you have more forward inertia. But too high speed and it doesn't want to turn because you have too much forward inertia to overcome. Think about it, you never really turn a bike except at low speeds, It's all about leaning the bike in the direction you want to go. Riding a motorcycle is a contant physics problem, all about competting forces you have to balance out. You also have to be aware you're going to have to put more counter force in to stand it up. I'm sure you know what I mean if you change lanes in a hurry you'll have to lean back towards the lane you came from to straighten the bike up. I don't know the term for it :don'tknow:

Anyway story short, yes the bike turns better at high speeds, but you'll have to know what to expect, and how to ride to handle those speeds. Get thee to a track me thinks. :thumbup:

 

[mlevins77]

Alright...time to get nerdy...

So far everyone is pretty much right...

The greatest force of resistance in leaning a bike over is the rotational forces of the wheels and everything on them that rotates with it (ie tires, brakes). The heavier your rotating pieces and the faster they are going...the harder it is to lean that bike without really turning the direction of rotation of the front wheel. These are "imaginary forces" in physics, and this on in particular is called centrifugal force. One direct example of this is your reverse steering...ie turning the opposite direction of the direction you want to go at high speeds.

Depending on the location of your rotating parts in your engine, they either will or won't affect the flipping of the bike. If the rotating parts are at the center of gravity (which changes dynamically based on rider position, suspension - sprung or unsprung, lean, etc) then they WILL NOT affect the centrifugal forces acting on the bike. When you lean over though...the center of gravity is actually outside of the bike (literally in the middle of nowhere) and those moving parts become a part of the equation.

Now take all this impractical knowledge and couple it with someone who has been knee-dragging for years and you'll come out with a hazy answer that won't make too much sense. Physics is a real sweetheart like that...you move one thing and the entire idea changes.

Just remember the basics of it all...your center of gravity determines how the forces react between the bike and road. Your body position, weight, bike weight, EVERYTHING come into play with the static and dynamic center of gravity (not moving and moving). The location of this center of gravity will allow you to either lean farther over or not be affected so greatly by lateral forces (cruisers and sportbikes).

If you would REALLY like me to I can work out some basic drawings to illustrate all this.

BS Mechanical Engineering
Georgia Institute of Technology
:Im With Stupid:

 

[GConn]

Too much wisdom for me here....

 

[reiobard]

I am impressed with the information in this thread, good job guys!

 

[Denver_FZ6]

Hang on a bit, I don't believe we're addressing Doorag's question. The way I understand his post, he's performing all turns at a constant speed of 55mph, but attempting the turn using different gears.

In this scenario, wheel rotational forces and suspension load will be the same, only engine speed will vary. How would higher engine RPM relate to easier turn-in?

 

[shaggystyle]

As a direct answer to the OPs question (that doesn't require a calculator), I've always read that you should enter a corner in the tallest gear that will allow you to stay in the powerband throughout the entire turn. This generally means you want lower RPMs, but not too low, when cornering. In practice I've found this produces smoother cornering and makes it easier to hold my selected line.

I am impressed with the information in this thread, good job guys!

I concur.

 

[bmccrary]

This should be posted on the "other forum" they might learn something from it...

Wait, I guess it would help if they rode first. Nevermind.

Good explinations guys.

I guess this could further prove the theory... "When in doubt, WOT!"

-bryan

 

[DefyInertia]

Hang on a bit, I don't believe we're addressing Doorag's question. The way I understand his post, he's performing all turns at a constant speed of 55mph, but attempting the turn using different gears.

In this scenario, wheel rotational forces and suspension load will be the same, only engine speed will vary. How would higher engine RPM relate to easier turn-in?

My thoughts exactly.

My guess at the answer: Increased engine braking = more weight transferred forward prior to apex + relatively soft forks = fork compression = geometry better suited to turning (same as raising the forks in the triple-clamps a few mm...shorter wheel-base etc....trail-braking with the front brake has the same effect).

 

[mlevins77]

Hang on a bit, I don't believe we're addressing Doorag's question. The way I understand his post, he's performing all turns at a constant speed of 55mph, but attempting the turn using different gears.

In this scenario, wheel rotational forces and suspension load will be the same, only engine speed will vary. How would higher engine RPM relate to easier turn-in?

You're absolutely right, with the thread taking a different direction we didn't actually answer the original question.

In theory with the RPM's higher, and we'll say for s's n g's that the rotating parts are dead smack in the center of gravity (COG), it's going to be harder to turn that baby over.

So my guess at this point, because it's getting late over here and I'm tired, is exactly what DefyInertia came up with. Without really knowing or feeling, Doorag must have changed the geometry of the bike and therefore the COG is repositioned allowing for an easier entry.

Of course it could be aliens too...they often do things like that from what I hear.

What's going to kill me is that now I'm going to have to completely figure this out when I get back to the States...thanks :Flip:

You kids play nice out there and stay away from gravel.

 

[D-Mac]

This thread is pretty interesting. I'm not sure I understand everything, but it's given me a lot to think about.

Keep it up! :thumbup:

I really need to do a track day....

 

[Wavex]

More rpms at turn in doesn`t necessarly mean you are braking... you could be accelerating as well (conf DefyInertia's ref to "more engine braking" ^^).

To me (I might be completely wrong here), more rpms at turn in means more vertical force (pistons going up and down), means harder to move the engine horizontally or to twist it on itself (lean). If you imagine the engine as a vertical centrifuge, the faster the centrifuge, the more difficult it`ll be to rotate the centrifuge.

I had noticed this during one of my videos... check out the link in my sign and click on "A bad ending to a great day"... the last 30 seconds summarizes it

 

[Fred]

Does anyone know which way the engine's crankshaft rotates? If it's rotating opposite the wheels, then it will actually be offsetting the gyroscopic effect of the wheels. Which means that higher crank RPM's will make the bike able to turn in quicker.

If it's the same direction as the wheels, then higher revs will add stability to the bike, making it turn in slower.

I don't have a service manual handy at the moment, so I cannot check it out myself.

 

[Wavex]

To get a gyroscopic effect you need more than just an axle moving on itself... I don`t think the crankshaft would offset anything... especially considering the size of the wheels, and the much larger gyroscopic effect you get from them... again, I may be talking out of my ass, but this is what I remember from physics class

 

[abacall]

Great thoughts here. To me the OP's question is simple. More RPM's give you more control of the throttle. As you go into the turn the higher RPM's allow for more compression braking (smoother turn-in), and more linear control of the throttle thus allowing for better throttle control on exit. As we all know, throttle control is key in turning.
So in summary:
Higher RPM's = better control of throttle.
Better control of throttle = smoother turn-in and exit from better power modulation.
Better power modulation = better turning.
Therefore Higher RPM's = better turning.

At least that's my view.

 

[Fred]

Wavex,

It won't be as big a factor as the effect from the wheels, simply due to the larger mass and diameter of the wheels. But it is a factor. I'm not sure to what extent it affects things.

The crank's rotation isn't enough to stabilize the bike on its own, that's certain. However, having ridden a wheelie on a BMW K-75, where the crank and all other rotating components run lengthwise through the bike, I can tell you that there is a very noticible effect. Sort of a "Holy ****, I'm about to die because the bike's up on one wheel and going sideways" kind of effect.

I don't recommend it.

Abacall, you got it right. Higher RPM's means better throttle control because you're in the power band as opposed to being on the edge of it. Add in the fact that a slight twist of the wrist at low throttle can easily double your throttle opening, while at higher throttle, it may only increase your throttle opening by 25% or so. This means that you have more delicate control over the throttle at larger throttle openings.

Fred

 

[abacall]

Wavex,

Add in the fact that a slight twist of the wrist at low throttle can easily double your throttle opening, while at higher throttle, it may only increase your throttle opening by 25% or so. This means that you have more delicate control over the throttle at larger throttle openings.

Fred

Exactly my thought. We all know how on/off the throttle can feel in the lower rpm's. That's not exactly confidence-inspiring when leaned in a turn.

 

[GTHappy]

BS Mechanical Engineering
Georgia Institute of Technology
:Im With Stupid:

When did you get out man?
I got a BS(00) and MS(02) in EE from GT.
Heh. Plenty of abbreviations there.

As for the original post, I haven't got a clue, but I did notice the same thing this weekend playing around with running in different RPM ranges. I'm a total noob, I know it and will admit to it immediately. Bought my bike in August and have been having a blast. :squid: