Leaning

[bomber]

It's really all about centrifugal force. At slower speeds, on a (top) heavy bike (especially), you have to counterweight, due to the lack of centrifugal force.

enjoy,

This statement makes no sense. Counterweighting, that is, putting more of YOUR weight on the outside, has nothing to do with less (or more) centrifugal force  . . . . .  if it was all about centrifugal force, counterweighting would make things worse, not better.

Note Bene -- I've not explanation for why counterweighting works a low speeds, but I recognize a logical fault when I see one ;-}

[bikerfish1100]

no, i think what he was saying is that at slower speeds there is a lack of centrifugal force (which pushes bike to outside and helps to hold it up against gravitational forces)- which thus creates a need to counterweight so as to overcome gravitational forces which want to pull the bike to the ground in the direction of the lean.

[AzItLies]

Maybe the best way to explain it would be to go back... way back... in the wayback machine...

Who else remembers the older movies, with Steve McQueen and Elvis Presley?

Do you remember when they would ride a motorcycle in those Carnival events?

They would ride in a kind of sphere thing... Some of those spheres would only go to a "half height", some a little higher.

They would start out riding the bike from the bottom of the sphere (of course). They would gradually go higher and higher as they increased speed. Eventually, after enough rotations, and going higher and higher ea time, as speed increased, they would almost be riding horizontally.

How did they do that?

It's the same principal as we are talking about in this thread... Centrifugal Force!!

Here's another way to conceptualize it... think about the sphere again... what would happen if the rider, from the start, rode from the beginning position (at the bottom of the sphere) and immediately went up to the middle? They wouldn't have enough speed (centrifugal force in this case)... and they'd just fall down!!

That's the difference we are talking about here in this thread. A slow, tight turn, has little or no CF to keep you upright, so you have to counter weight.

A faster tight turn has the CF to keep you upright, and to keep the bike even more upright we can lean in (our bodies), and maintain that lean angle and CF.

Remember from your BRC class... there are 2 ways to turn a motorcycle: At Slower Speeds, We Have To Use The Handlebars... At Faster Speeds We Have To Make The Motorcycle Lean...

Think about those 2 statements... it will all make sense...

[chamartia]

I'm curious -- did you try the exercise I mentioned in a previous message? I'll repeat it here:

Here's another thing to try. Stand by your motorcycle, hold it vertical, turn the handlebars full lock left, and turn it in a circle. After you've done this, lean the motorcycle as far as you feel comfortable, turn the handlebars full lock left, and again turn the bike in a circle. Measure the radii of the two circles. What do you notice?

cbsn:

I didn't try it, as I didn't realize that you were suggesting it as something counterintuitive. I take it that the clear intuition would be that leaning the bike over will cause the radius to be smaller, but the fact that you've followed up on it implies that's not the case.

I don't have a driveway, so there's no easy place for me to do this. So what's the claim?

Cheers,
.cyb

[cbsnbiker]

cbsn:

I didn't try it, as I didn't realize that you were suggesting it as something counterintuitive. I take it that the clear intuition would be that leaning the bike over will cause the radius to be smaller, but the fact that you've followed up on it implies that's not the case.

I don't have a driveway, so there's no easy place for me to do this. So what's the claim?

Cheers,
.cyb

It's not counterintuitive. You're right -- the radius will be smaller with the bike leaned over.

The reason I suggested doing it is that many people are surprised at how much smaller. It's not a subtle difference. Also, you seem to like working through this sort of thing, so I thought you might have actually done it.

You wouldn't have to do it in a driveway. A parking lot works just great.

[sfalexi]

Don't look at YOUR weight, look at the BIKE'S weight.  A bike typically weighs at LEAST twice the rider, and in my case, almost 4 times as much as me.  When you counterweight, you are leaning the bike further which pushes the COG inward towards the center of the circle.  This makes the circle tighter and quicker.  When YOU lean in, the BIKE is staying upright, shifting the COG OUTWARDS.  The bike's mass effects the COG much more than your body.  

Also, try thinking about what's needed to maintain a straight line.  You can lean the bike to the left and lean your body out to the right and the bike will maintain a straight line.  So if that entire form leaned further to the left, your body would be upright, the bike leaned further to the left, and you would start to curve to the left.  Any handlebar turn would make the curve tighter.

Let's take the reverse idea.  You lean to the left, and the bike will lean slightly right.  But you STILL want to tighten the curve to the left.  So you lean yourself and the bike further to the left, and the bike will start to curve left.  But eventually, your body will contact the ground.  The next step to tighten the curve, would be to leave your body as is and now bring the bike to your body, shifting that COG left.  But again you hit a limit to the lean angle.  So you raise your body away from the pavement, allowing the bike to lean a little more, and that would be a small counterweight.

I'm not sure I can prove the physics, but from my observation, the idea of counterweighting is also to maintain a tight curve with less speed.  If you watch the DVD's (or look up youtube advertisements) for "Ride Like a Pro", you'll see they stay with the bike, neither leaning inwards or outwards.  Just with the bike.  However their speed through tight turns looks to me to be greater than someone who is counterweighting.  That means it takes more time and distance to brake or fix a line.

In addition, when you counterweight, it's MUCH easier to take the bike and swing it the other direction.  You have more force to apply to the other handlebars to make it stand upright and then lean over the other direction.  Try riding straight and keeping your body upright and pushing the bars left and right to initiate a slight weave.  Then keep your body in line with the bike (if there's a backrest, glue your back to it) and do the same thing.  The weave is quicker the first time, cause you have more leverage to bring the bike back out of it.

For real-world riding (uturns on a street or at a light, swerving to avoid the door that just opened), you get a quicker reaction-time and greater control by leaving your body upright.  Even MORE control when you counterweight.  For maintaining maximum speed during a sweeping turn, you lean your body in, leaving the motorcycle's geometry to remain as stable and unchanged as possible and don't turn that front wheel.

If you noticed in the japanese video, not ONE of that rider's turns were as sharp as the harley's turns.  Faster, yes, but not as small a circle.  And with a shorter wheelbase, that should have HELPED.  But it was very quick through the sweepers.