Active dynamics

Ive heard of terms like "Ice cream cone effect" and 'Centrifugal force".

Can these two areas be affected by peg weighing together or independently and have an effect on your line while exiting a corner?

 

There is a sort of chicken and egg dlemma here isn't there. Does the front tire guide the rear contact patch on a tangent to the original line and make the bike turn or do the combined forces rotate the rear tire around to its new position wrt the original line.

It occurs to me that getting the rear contact patch to rotate into the corner, to agree with the intended arc, is the greatest resistence to overcome in the process of steering.

That would mean that the front takes its final angle only after the rear has stabilized on its new path. The rear contact patch has to break traction to some degree or the bike wouldn't turn. It is being dragged across the pavement at an angle.

My take is--whatever can generate enough force to make that rear tire rotate on a vertical axis could be called steering.

Putting a 190 on a bike that has had a 180 on it makes a definite change in the bike's resistance (harder) to CS input.

There are other factors being discussed but if this is the greatest resistance to overcome then most of the weaker links like gyroscopic forces can really be overlooked as insignigicant can't they?

Keith

Keith

 

Putting a 190 on a bike that has had a 180 on it makes a definite change in the bike's resistance (harder) to CS input.

You need to be carful here as most 190s are "50" series and are smaller diameter than the 180/55 tires. Installing the smaller diameter tire (190) increases the trail making the bike more stable, and requiring more input (effort) to turn the bike.
The more round, and wider shape of the 190 is also a factor, and that is what I believe you were referring to.

 

You need to be carful here as most 190s are "50" series and are smaller diameter than the 180/55 tires. Installing the smaller diameter tire (190) increases the trail making the bike more stable, and requiring more input (effort) to turn the bike.
The more round, and wider shape of the 190 is also a factor, and that is what I believe you were referring to.

a 190/55 tire will prove this by behaving like a 180/55 in flickability

 

a 190/55 tire will prove this by behaving like a 180/55 in flickability

A 190/55 mounted on a 6" rim has essentially the same profile as does a 180/55 mounted on a 5.5" rim.

 

yep, thats my point!

 

That would mean that the front takes its final angle only after the rear has stabilized on its new path. The rear contact patch has to break traction to some degree or the bike wouldn't turn. It is being dragged across the pavement at an angle.

My take is--whatever can generate enough force to make that rear tire rotate on a vertical axis could be called steering.

Putting a 190 on a bike that has had a 180 on it makes a definite change in the bike's resistance (harder) to CS input.

Keith

Keith

the 180 and the 190/55 have similar handling. the 190/50 is different, but has the same tread section, so the "break traction" theory doesn't seem to work.
( it does work on my shifter cart because the rear axle has no differential)

 

I don't believe that the rear actually breaks traction at any point.. You have your contact patch and the traction is the total between the grip of all the compound molecules.. Your tire should be rotating fast enough to place a new patch down fast enough to keep all rotational force within the limits of the compounds flexibility.
Also, keeping in mind that the tortional force of CS originates from the front, I would think that the final angle of the steering column would be based more on the profile of the front tire than the roll of the rear.

 

It looks like this thread has died.

I just want to thank the contributors of this thread and special thanks to the techies and celebrities. You guys :rock :bow

This topic covered a great deal of data that average riders like me never ever think about(ie Angular momentum, polar moment of inertia). Although there seems to have been no agreement as to the definition BS, this topic brought out the basic physics of how a motorcycle turns, where rake and trail come into play, where shifts in CoG affect the bike's steering, etc.

As has been said many times, BS cannot accurately steer the bike but I think that BS can't be discarded away either.

So anyways, I learned a lot. Thanks.

 

First of all...

Huh?

You said. "You need to be carful here as most 190s are "50" series and are smaller diameter than the 180/55 tires. Installing the smaller diameter tire (190) increases the trail making the bike more stable, and requiring more input (effort) to turn the bike.
The more round, and wider shape of the 190 is also a factor, and that is what I believe you were referring to."

I think this is more accurate. The 190 refers to the width of the tire. 190mm tobe exact.

The 50 refers to the sidewall height (profile) of the tire. It is a percentage of the width of the tire.

The examples cited are 190/50 and 180/55. 190 x .50 = 95mm
180 x .55 = 99mm. Is that what you mean by them being a smaller diameter? 99 is smaller than 95, I agree. But how does that have anything to do with diameter.

di·am·e·ter ( P ) Pronunciation Key (d-m-tr)
n.
Abbr. d or diam. Mathematics.
A straight line segment passing through the center of a figure, especially of a circle or sphere, and terminating at the periphery.
1. The length of such a segment.
2. Thickness or width.
3. A unit for measuring the magnifying power of a microscope lens or telescope, equal to the number of times an object's linear dimensions are apparently increased.

I'm going with #2. That means that the 190 tire has a larger diameter left to right than the 180.

If you are talking about the size of the circle made up of the tire, then the "180" profile would actually make the tire "taller". Therefore increasing the trail. I think we are saying the same thing. Just trying to get clarification. Here is a good link for those who are confused or just want to have a basic idea of rake and trail. http://www.stripbike.com/rake.html

 

flickability

Injured an old unjury--flat on my back for the past few days,

If you duplicate the ride heights and rim widths of the bike and put a larger rear patch on the pavement, the bike is more sluggish in turning, harder to flick.

This was a point I learned from Rainey from the endless tire testing he used to do. Take it for what it is worth.

Now whether the tire scrubs across the pavement when you turn the bike is still a question I have. The tire may squirm enough on a treaded tire, I wonder if it will on a slick?

Also, consider that the tire is theoretically stopped on the pavement at any given instant of time. It must in order to maintain traction. I theorize that a quick flick at most any speed over 35 MPH scrubs it sideways, pretty much has to, no tire can squirm that much.

Anyhow, the point of that whole thing was that the rear is the most planted part of the bike until a good deal of weight transfers to the front under braking or just off throttle.

We say, and I have thought many times, that the reason the bike turns easier with weight tranfered forward is totally a result of the rake and trail changes but I believe that the rear contact patch surface loading and area have an effect on it.

Keith

PS: let's go for 1,000 posts, don't wimp out now.

 

Re: First of all...

Huh?

You said. "You need to be carful here as most 190s are "50" series and are smaller diameter than the 180/55 tires. Installing the smaller diameter tire (190) increases the trail making the bike more stable, and requiring more input (effort) to turn the bike.
The more round, and wider shape of the 190 is also a factor, and that is what I believe you were referring to."

I think this is more accurate. The 190 refers to the width of the tire. 190mm tobe exact.

The 50 refers to the sidewall height (profile) of the tire. It is a percentage of the width of the tire.

The examples cited are 190/50 and 180/55. 190 x .50 = 95mm
180 x .55 = 99mm. Is that what you mean by them being a smaller diameter? 99 is smaller than 95, I agree. But how does that have anything to do with diameter.

di·am·e·ter ( P ) Pronunciation Key (d-m-tr)
n.
Abbr. d or diam. Mathematics.
A straight line segment passing through the center of a figure, especially of a circle or sphere, and terminating at the periphery.
1. The length of such a segment.
2. Thickness or width.
3. A unit for measuring the magnifying power of a microscope lens or telescope, equal to the number of times an object's linear dimensions are apparently increased.

I'm going with #2. That means that the 190 tire has a larger diameter left to right than the 180.

If you are talking about the size of the circle made up of the tire, then the "180" profile would actually make the tire "taller". Therefore increasing the trail. I think we are saying the same thing. Just trying to get clarification. Here is a good link for those who are confused or just want to have a basic idea of rake and trail. http://www.stripbike.com/rake.html

:2bitchsla

dan knows exactly what he is talking about..

180/55 will have a larger diameter.. definition #1.. 180/55 will be taller than a 190/50..

a taller rear tire will raise the rear.. reducing rake and trail..
if you restored rake and trail by dropping your rear ride height it would still flick a little easier cos of the profile.

a taller front would increase trail but thats not we are talking about.

keith.. a 1000 posts..
we can argue all we want but i doubt we'll get anywhere without a good complete analysis..
like say a simulation.. or some data loggin system that some how measures rider movement over the bike.

also the more you look at it.. it becomes obvious that there a ton more forces at play than can be figured out in most peoples heads.. e.g. not only is the riders C.G. important but the orientation also seems to come into play when you try to twist around the bike... this might be why most studies don't even go there.. most just assume that all a rider can do is apply steering torque about the stem, brakes and throttle.

the more i try to figure out the less i seem to know about tire forces, suspension interactions , moment of interias of various components etc... all the thing required to fully figure this out.. so i don't have much to say.

but it should help to listen to you have to say about rider experiences etc and all the thought you have put into this.. hopefully sometime soon somebody smart enough to figure it all out will stop by and explain...

vishnu

 

Re: First of all...

Huh?

You said. "You need to be carful here as most 190s are "50" series and are smaller diameter than the 180/55 tires. Installing the smaller diameter tire (190) increases the trail making the bike more stable, and requiring more input (effort) to turn the bike.
The more round, and wider shape of the 190 is also a factor, and that is what I believe you were referring to."

I think this is more accurate. The 190 refers to the width of the tire. 190mm tobe exact.

The 50 refers to the sidewall height (profile) of the tire. It is a percentage of the width of the tire.

The examples cited are 190/50 and 180/55. 190 x .50 = 95mm
180 x .55 = 99mm. Is that what you mean by them being a smaller diameter? 99 is smaller than 95, I agree. But how does that have anything to do with diameter.

di·am·e·ter ( P ) Pronunciation Key (d-m-tr)
n.
Abbr. d or diam. Mathematics.
A straight line segment passing through the center of a figure, especially of a circle or sphere, and terminating at the periphery.
1. The length of such a segment.

I hate to even reply to this, as I feel that a discussion on tire sizes doesn’t even belong in this thread. However, I hate to see you continue to be confused, mshumake. Dan, is right, and you proved it. The diameter that he was speaking of is per your definition #1. The total diameter is made up of the wheel diameter, and twice the sidewall height that you calculated. Hence, the 180/55 is slightly larger in DIA than the 190/50. This change in overall DIA is what changes the rear height, and therefore the bike’s geometry (rake & trail).

However, I feel that the main difference that a 180/55 is more “flickable” (a term that I hate to use when describing motorcycle riding), is because of it’s shape/profile. Since it is taller and skinnier, as you mentioned, it must be more rounded. That is what makes it easier to turn, and less stable. I haven’t tried it, but I hear that a 190/55 has a similar feel, but is still wide, so it’s kind of the best of both worlds.

 

discovering CS & BS

I wish that everyone on this forum could come out to a track where two bikes were set up with full data acquisition systems and a set of No BS bars on one or both of them. At the track we would determine what was and what was not being done on the bike and if it had mil spec GPS we could see within inches if the line was or was not varying from the inputs--corelate the two data streams and we'd have a hell of a party and lots of data to get drunk on!!!

I am engaged in a project to build a system with these capabilities for another training bike that is in progress.

For right now and for my needs in life I can't come to a resolution on how to train body steering. I can achieve a definite understanding with my students on CS so I'll stick with that for now.

If anyone comes up with a way to present BS accompanied by a logical way to explain it and train it, let me know.

For the record, I've never said that BS doesn't exist only that it wasn't a fast, predictable and accurate way to alter a motorcycles direction.

Arwuns situation with the No BS bike typifies several key issues discussed over the past weeks on BS Vs CS.

1. The No BS bike confuses even highly expereinced riders. Arwun had surprises, so have 1,000's of other riders.

2. Unable to immediately identify what specific sequence of actions make it turn, riders panic and become unable to correct their line. Arwun did not want to hit the wall.

3. It does take a combination of body actions to make it alter course.

4. The combination of actions needed are not natively understood by riders.

5. The combination of actions needed are not what they thought was making it alter course. If they were, corrections would be easy, control would be difinite, walls would not be hit.

6. Once a rider does figure out the sequence of actions there is a definite lag (minimum of 1/2 second) between the execution of them and any change in direction. Trevitt's film on TV was a good example of that. My video on the school's web site shows it as well.

I'm definitely in the CS camp when it comes to tank pressure and peg weighting. Isolated from any other input into the bike or movememnt on it, they are good leg exercises period.

A relatively stable body location anywhere on the bike can no more be classified as a steering action than can adjusting the suspension or chassis geometry be called steering.

Riders' observations on the subject of BS Vs CS are unreliable and contrary at best.

The NO BS bike brought CS Vs BS squarely into the public eye. One of the benefits has been that the BS only guys have withdrawn from that unsupportable position and now acknowledge CS, which they did not before.

(I went to a hard line BS school once and the class was told by the instructor that CS was something made up by a bunch of journalists a few years ago. They don't say that anymore. That is good for their students.

Some of the exercises and theories I've seen over the past few months as proof that BS is effective have proven to be poor observation and junk science. Even so, they were reported to the public as "fact". Even now, we here don't agree on some points after many intelligent and informed statements made on the subject.

Another lesson I've learned is that having a fixed idea is no way to research.

Keith

 

Re: discovering CS & BS

Keith,

What is "steering" to you? Do you consider a subtle line change "steering"? Or does one have make a significant line change for "steering" to have taken place.

Personally, I think "steering" is anything done on the bike that alters the line the bike is taking.

Scott

 

scott,

Do you consider leaning steering?

 

If you duplicate the ride heights and rim widths of the bike and put a larger rear patch on the pavement, the bike is more sluggish in turning, harder to flick.

Yes, absolutly, how much of that is the size of the tire patch and how much due to the shape of the tire?? The taller tire also has a "longer" patch.

This was a point I learned from Rainey from the endless tire testing he used to do. Take it for what it is worth.

I would take it.
I have a Rainey question, a long time ago I heard that Wayne, at times, used 250 GP tires for qualifying instead of 500GP tires on his 500GP tires. The advantage being they turned so much better, as they were not as wide and perhaps a different shape. Somehow I have a feeling you may know if this is correct.

 

scott,

Do you consider leaning steering?

Leaning is a result, not an action. If I hang off the bike more, and it leans more, the line will change. I would call that steering.

Scott

 

i'd call it leaning

 

Leaning is a result, not an action. If I hang off the bike more, and it leans more, the line will change. I would call that steering.

Scott

Fair call.

 

steerig definition

Scott,

I defined what I meant by steering back on about page 5 of this thread.

Dan,

Wayne never said anything to me about that but I'll ask him and let you know.

------------------
Leaning is a result, not an action. If I hang off the bike more, and it leans more, the line will change. I would call that steering.
Scott
-------------

Scott,

Have the physics reversed over the past few weeks? All factors of speed, arc and chassis adjustments being equal, when the rider hangs off the bike leans less. You know that. Did I miss something?

Keith

 

Re: steerig definition

------------------
Leaning is a result, not an action. If I hang off the bike more, and it leans more, the line will change. I would call that steering.
Scott
-------------

Scott,

Have the physics reversed over the past few weeks? All factors of speed, arc and chassis adjustments being equal, when the rider hangs off the bike leans less. You know that. Did I miss something?

Keith

I think that he meant that as you lean off of the bike, it leans easier, not necessarily more. If you are in a turn and lean off of the bike, it will lean more, if you let it turn sharper. If you stay at the same speed and same radius, then it will have to lean less to compensate for the change in CoG, and keep the forces equal.

 

Re: steerig definition

Scott,

I defined what I meant by steering back on about page 5 of this thread.

------------------
Leaning is a result, not an action. If I hang off the bike more, and it leans more, the line will change. I would call that steering.
Scott
-------------

Scott,

Have the physics reversed over the past few weeks? All factors of speed, arc and chassis adjustments being equal, when the rider hangs off the bike leans less. You know that. Did I miss something?

Keith,

Then you definition of the word "steering" is still too limited. You need to add some words around the word "steering" for your definition.

Also, if you hang off a bike more, yes, the lean angle of the bike will need to be less if you maintain the same speed and arc in the turn. But the line the bike will run will tighten the more you hang off.

Example that is easy to see: Hang off a bike that is going straight, the bike will turn the direction you are hanging off if you do not countersteer to keep the bike going straight.

All the steering techniques that work on a dirt bike work on a road bike. They are just a little more subtle. Even you concede that you can body steer a dirt bike. Peg weighting plays a big role is steering and controlling a dirt bike. Just because you have a hard time figuring out how to explain or teach these techniques does not mean you should discount them or suggest they are not worthwhile.

Scott

 

Re: discovering CS & BS

Arwuns situation with the No BS bike typifies several key issues discussed over the past weeks on BS Vs CS.

1. The No BS bike confuses even highly expereinced riders. Arwun had surprises, so have 1,000's of other riders.

2. Unable to immediately identify what specific sequence of actions make it turn, riders panic and become unable to correct their line. Arwun did not want to hit the wall.

3. It does take a combination of body actions to make it alter course.

4. The combination of actions needed are not natively understood by riders.

5. The combination of actions needed are not what they thought was making it alter course. If they were, corrections would be easy, control would be difinite, walls would not be hit.

6. Once a rider does figure out the sequence of actions there is a definite lag (minimum of 1/2 second) between the execution of them and any change in direction.
Keith

Boy, a lot of stuff sure could have been avoided if those points were made clear before my ride from hell. Oh well, live and learn I guess. Next time I will trust my instincts.

 

Re:Affects of dynamics

Are the dynamic inputs and reactions on the no BS bike the same upright and leaned over at speed, on the gas etc.?

Re: Lap times
If you built a bike where you completly negated body steering inputs, would lap times be adversely affected?

Man, this can of worms thread is confusing.
Rick