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Discussion Starter #1
Okay guys I have a little question here that I would appreciate your help with.

At the following speeds how much of a lean angle do you think you could be at before having the bike tip over or lose control on you. I kno that its possible to get to learn a certain angle for a fraction of a second at low speed but think more of time in about 1-2 seconds.

Speed Angle
20 ?
30 ?
40 ?
50 ?
60 ?
70 ?
70+ ?

Thanx
 

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well, it depends on your tire and your bike really
 

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Discussion Starter #3
I know theres a lot of variables but im just looking for opinions on what the angle would be. I know there is no one single right number but im just trying to get an average baseline. Its for a school project im doing
 

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Not sure on any numbers, but I do know that the slower that I go, the less lean angle that I want. Faster speeds the bike seems to be more stable.
 

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Don't know about anyone else, but to even guess at lean angle measured in degrees while on a bike is something I can't do. From a third person perspective, it may be easier, but then you don't know how fast the bike was going.

It's also a very subjective question. I like to hang off when running through twisties. You use less lean angle when hanging off for any given speed, than if you don't.

Peace
 

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During the summer, I was doing a track day at Spokane!!! I was riding a '02 R6 and taking right-handers as slow as 65kmh!!! I ended up dragging knee, toe, and PEG!!! I dunno how much slower you could do it though!!!

 

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Dude,
Theoretically, any bike WILL lose traction for the same set of tires at exactly the same speed. The weight of a bike is not a factor for this, since the forces that cause your bike to lose traction (centrifugal forces during a turn etc.) are dependent on the weight, and are exactly balanced by the forces that provide traction (like rolling friction, and reaction forces from the road), also dependent on the weight.
It is safe to tip a bike over until it is scraping hard parts, coz tipping it beyond will certainly result in a crash. This is as long as you are going fast enough to balance the forces tending to make your bike lose traction, with the ones that are keeping you on. So there, the theoretical limit for a lean for a bike with the right tires on is until its scraping hard parts. This is my take on the issue. Corrections from more qualified physicists are welcome..;)
 

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sopan_shadowfax said:
Dude,
Theoretically, any bike WILL lose traction for the same set of tires at exactly the same speed. The weight of a bike is not a factor for this, since the forces that cause your bike to lose traction (centrifugal forces during a turn etc.) are dependent on the weight, and are exactly balanced by the forces that provide traction (like rolling friction, and reaction forces from the road), also dependent on the weight.
It is safe to tip a bike over until it is scraping hard parts, coz tipping it beyond will certainly result in a crash. This is as long as you are going fast enough to balance the forces tending to make your bike lose traction, with the ones that are keeping you on. So there, the theoretical limit for a lean for a bike with the right tires on is until its scraping hard parts. This is my take on the issue. Corrections from more qualified physicists are welcome..;)
It depends on a bazillion factors, which I dont have time to list :D

weight transfer. If you are on throttle off throttle will play a huge role. Same rider in a corner may be hard on gas and lose traction at say 20 degree lean, while another with mild accel. may be at 25 degree.

Set up of the bike. If you have the suspension fooked, you will not be able to lean nearly as far.

Some bike jsut dont turn as well as others, for example, I ride a BMW K1200 LTC sometimes. Almost 900lbs of bike. I can not lean nearly as far as I can on say, my Mille, even though the K1200 has better tires. The LTC has way more weight to throw around, thus making it harder on the tires to stay on track in a hard corner. The bike needs more lean angle to make it turn the same.

Also different geometry plays a huge role of the effects of cornering. The rake on a chopper causes the max speed at lean angle X to be way lower than the max speed at lean angle X on a sport bike.

Now, I am no mechanic, and I just made all this up, so anyone feel free to correct me, but only if you know what you are talking about.
 

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XX,

Your lean angle is determined only by speed and turning radius (assuming your body position is the same).

The higher the speed, and/or the tighter the radius, the more lean required. It's as simple as that. For any speed you indicated, you can go to extreme lean angle if taking a tight turn (small radius), or very light lean angle by taking a wider turn (b***** radius).

Of course, taking a tight turn at 20 mph and dragging a knee takes a lot of skill.

Edit: just noticed you were doing it for a project. So, here is a bit more science. The reason a motorcycle (as well as any other one track vehicle) has to lean in a tun is to compensate for a centrifugal force which wants to push you out. The faster you go, or the tighter turn you try to make - the stronger the centrifugal force becomes. So, we have no other choice, but to lean the bike more.

By the same token, if you try not to lean the bike as much, it will ride along the line corresponding to greater radius - thus running wide. And, conforming to the equation.
 

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Discussion Starter #11
IG. said:
XX,

Your lean angle is determined only by speed and turning radius (assuming your body position is the same).

The higher the speed, and/or the tighter the radius, the more lean required. It's as simple as that. For any speed you indicated, you can go to extreme lean angle if taking a tight turn (small radius), or very light lean angle by taking a wider turn (b***** radius).

Of course, taking a tight turn at 20 mph and dragging a knee takes a lot of skill.

Edit: just noticed you were doing it for a project. So, here is a bit more science. The reason a motorcycle (as well as any other one track vehicle) has to lean in a tun is to compensate for a centrifugal force which wants to push you out. The faster you go, or the tighter turn you try to make - the stronger the centrifugal force becomes. So, we have no other choice, but to lean the bike more.

By the same token, if you try not to lean the bike as much, it will ride along the line corresponding to greater radius - thus running wide. And, conforming to the equation.
You basically hit on what I was trying to get form this post in the first place. The project that I am working on is writing a sample program that will take into account the speed and bank angle of a bike and for the "Average rider" (skill still yet to be determined) will determine if the rider and or bike will be in a crash situation.

I understand that there are many many factors almost too many to list when it comes to how low the "average" rider can lean a bike without it falling over. Thats why I was looking to the sportbike network for opinions from many different riders as to how far they can lean the bike over at certain speeds and then calculate an average and possibly extrapolate or interpolate some type of formula.

As for myself this is just a quick guess but here is what I feel I could do as far as speed vs lean angle where the degrees from straight up and down

Speed Lean Angle
20 5-7 deg
30 7-15
40 15-30
50 30-40
60 40-45
70+ 45+
 

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xxdcmast said:
Okay guys I have a little question here that I would appreciate your help with.

At the following speeds how much of a lean angle do you think you could be at before having the bike tip over or lose control on you. I kno that its possible to get to learn a certain angle for a fraction of a second at low speed but think more of time in about 1-2 seconds.

Speed Angle
20 110
30 90
40 80
50 70
60 60
70 50
70+ 40

Thanx
haha just playin , no offence but thats a dumb/hard question, there WAY WAY to many varibales like others have said, road cond, tires,bike,pavement surface,out side temp, road temp, ALOT!
 

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Perhaps I should elaborate...

The ONLY forces acting on a bike in a turn are the static friction of the tire rolling on the road (Lock the rear wheel, this turns into kinetic friction, which is lower, the explanation for highside or powersliding), the force of gravity on the bike, the normal force of the road pushing back on the bike, and the force on the bike as governed by Newton's first law. The reason riders imagine they are being pushed to the outside is because it is the nature of the motorcycle to resist changes in its motion, such as a change in direction. The motorcycle resisting the change in its motion is the force riders feel, and if this force exceeds the friction on the road (governed by the coefficient of static friction and that normal force of the road on the bike), then the bike will be unable to maintain its line, and may crash on the outside of the turn.
 

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I pretty much agree with IG and IM. Even though there is technically no such thing as centrifugal force, it is a handy layman's term to describe certain effects. I will look at past track photos to see if I can help out with this project. From the photos I can figure out angle, but remembering approximate speeds may be tough (who looks at their speedo on the track?).
 

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12RPilot said:
I pretty much agree with IG and IM. Even though there is technically no such thing as centrifugal force, it is a handy layman's term to describe certain effects. I will look at past track photos to see if I can help out with this project. From the photos I can figure out angle, but remembering approximate speeds may be tough (who looks at their speedo on the track?).
... pretty easy to see it when you have a camera mounted on your tank!!! :popcorn
 

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Summary of Main Data (if say the bike were on rails)

Speed
Radius of Turn
Camber of Road
Center of gravity (changes with weight and position of rider)

I think that about sums it up. If you can find all those peices of information you should be able to determine the soeed, angle and position nessesarry for a turn.
 

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I recall someone posted an excell sheet with this problem a long ways back.
IG is right, standard simplifying assumptions made, you need to have turning radius and lean angle and speed in your equatioin. Just draw a free-body diagram with the forces acting on the bike.

Here's a few hints to get you going; I'm not going to do it for you cause then you would learn nothing. The centripetal force causing the bike to go around the turn will give you the centripetal acceleration V^2 /R and is the sum of all the forces acting on the bike. Forces acting on the bike are the gravity force (at the c of g), and the road-tire force (normal and friction components). The bike will be stable at a given lean angle if the torque about any point is zero. Balance torque about the c of g, and the normal force and friction force will have different lever arms so you can calculate the angle, assuming you have enough friction (Ff=mu Fn). You could balance the torque about the road/tire interface and balance the gravity force and the rate of change of momentum (same units as force).

I personally have ground footpegs at all those speeds (my bike originally came with peg feelers, but for some unknown reason they dissapeared ), and must say that it's scarrier at higher speeds.
 

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You're writing a computer program to do the calculations??? Then get a hold of a book by a gentleman named Gaetano Cocco called "Motorcycle Design and Technology." He has a PhD in Mechanical Engineering, so your inner geek can have all kinds of fun playing around with the 900 equations he published to determine this, that, or the other aspect of riding a motorcycle.

Scott :)
 

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IMPerfection,

I respectfully disagree with your statement "there is no such thing as centrifugal force". You are implying that in the end we deal with the resultant force, where centrifugal force is compensated by the force of gravity.

But, saying there is no such thing is like saying there is no gravity, a person simply stands on the ground.

Take a string, and attach dynomometer (measures force) to it, and some weight to the dynomometer. Then, start spinning the string around, above your head, and see that the faster you spin it, the b***** number the dynomometer will show. So, which force it shows?

Anyway, back to original problem. XX, you need an equation.

Well, centrifugal force... I did a search on Yahoo, and here is a link to the thread which discusses centrifugal force - click here.

The other force (part of gravity) which compensates is simple. It's just a cos, or sin of the lean angle multiplied by the weight of the bike. Of course, we make an assumption that the bike/rider have centralized mass, etc.

But, I am really interested to see the results of your project. Could you please post it here.
 
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