Counter steering vs weighting the pegs/body steering

[rcgldr]

Show him a picture of a motorcycle leaned over in a corner with its front wheel off the ground and watch his head explode. Also the gyroscopic force that he dismisses as laughable has more effect on a motorcycle.

Cornering while doing a wheelie still requires countersteering (via the rear tire alone), camber thrust and slip angle or relying of momentum built up before the front wheel lifts off the ground. In the case of unicycles, there's no trail effect to induce some "automatic" countersteering in response to weight shifting, a unicycle rider has to consciously countersteer to lean. Advanced riders control countersteering by varying pedal pressure with minimal arm motion, while novices mostly use arm motion or do a series of jerk movements to turn. In the unicycle community, there's no debate about weight shifting versus countersteering, countersteering is recognized as the only way to control lean angle and path in a turn. In this video, the rider is moving his arms and using pedal pressure to lean and countersteer. He may have done that in order to make the countersteering more obvious.

https://www.youtube.com/watch?v=55n90QAxRSk

The centripetal force applied from the pavement to the contact patch of a tire still results in deformation, although it would be small in the case of a unicycle.

that author did a good job of showing that 2-wheeled vehicles use steering angle to accomplish some turning. but he didnt show the relative magnitude compared to camber thrust and def didn't show that camber thrust has zero effect. I will say that I did forget about the idea that lean angle increases the effective steering angle.

I think it'd take one more experiment to show that camber thrust has some effect. maybe it'd even reveal some relative magnitudes. compare 2 vehicles w/ the same lean, but with diff camber on the tires. See which vehicle has a tighter turning radius. compare natural steering angle too just in case they are different. and if they are diff, maybe only change the camber of the rear tire.

In the case of camber thrust at the front tire, the torque goes into the handle bars, not the frame, since the front tire can pivot (about its steering axis) but not the frame (since the rear tire would have to slide sideways to allow the frame to pivot). If the camber thrust was significant, the rider would feel the torque related to camber thrust, but other factors have more of an effect on what the rider feels at the handlebars.

As posted above, camber thrust at the rear tire would try to turn the frame, but the front tire prevents this (again other than a small amount of tire flex).

Also, since contact patch deformation in a turn means the actual radius is greater than the "steered" (geometrical radius if there was no tire flex), there's always an effective slip angle at the front and rear tires in a turn (both tires are oriented slightly inwards of the curved paths of the contact patches).

 

[stangmx13]

In the case of camber thrust at the front tire, the torque goes into the handle bars, not the frame, since the front tire can pivot (about its steering axis) but not the frame (since the rear tire would have to slide sideways to allow the frame to pivot). If the camber thrust was significant, the rider would feel the torque related to camber thrust, but other factors have more of an effect on what the rider feels at the handlebars.

As posted above, camber thrust at the rear tire would try to turn the frame, but the front tire prevents this (again other than a small amount of tire flex).

Also, since contact patch deformation in a turn means the actual radius is greater than the "steered" (geometrical radius if there was no tire flex), there's always an effective slip angle at the front and rear tires in a turn (both tires are oriented slightly inwards of the curved paths of the contact patches).

theres too much going on with the steering head to rule out a camber thrust force because u cant feel it in the bars. this is especially true since the distance and angle of the torque from the steering head are unknown.

the frame doesn't need to yaw for the moto to turn more or less. imagine u are turning and a gust of wind blows u further into the corner. imagine if the gust of wind only blew onto the rear tire. what happens? just tire flex? no. u turn more. be careful to not over-simplifying.

ive done back to back rear tire profile tests. changing to a steeper profile does make the moto turn a tighter radius for comparable inputs. when the suspension was later optimized for that new steeper profile, the moto turned even better. we can assume my suspension was optimized for both and that my riding didnt change dramatically over a few hours, suggesting that the net effects were due mostly to the camber change.

 

[rcgldr]

the frame doesn't need to yaw for the moto to turn more or less.

I don't see a reason for twisting effect at the contact patch to translating into a linear force, unless the twisting results in a yaw and turning as in the case of a single rolling cone.

ive done back to back rear tire profile tests. changing to a steeper profile does make the moto turn a tighter radius for comparable inputs. when the suspension was later optimized for that new steeper profile, the moto turned even better. we can assume my suspension was optimized for both and that my riding didnt change dramatically over a few hours, suggesting that the net effects were due mostly to the camber change.

Assuming tire stiffness remains the same, the contact patches at the front and rear tires follow the same paths, but with a steeper rear tire profile, the rear of the bike will be offset outwards more due to lean angle, resulting in a frame that is yawed inwards more, and requiring a smaller steering angle relative to the frame, but the steering angle relative to the contact patch paths will be about the same (both tires still oriented slightly inwards of their actual contact patch paths, depending on relative stiffness).

 

[stangmx13]

Assuming tire stiffness remains the same, the contact patches at the front and rear tires follow the same paths, but with a steeper rear tire profile, the rear of the bike will be offset outwards more due to lean angle, resulting in a frame that is yawed inwards more, and requiring a smaller steering angle relative to the frame, but the steering angle relative to the contact patch paths will be about the same (both tires still oriented slightly inwards of their actual contact patch paths, depending on relative stiffness).

nah. this is either backwards or just incorrect, depending on which way u look at it.

assume the steeper tire is the same height and width, just steeper for moderate to high lean angles.

 

[tzrider]

nah. this is either backwards or just incorrect, depending on which way u look at it.

assume the steeper tire is the same height and width, just steeper for moderate to high lean angles.

Robert, by steeper, do you mean the profile is more round than v-shaped? Something may be getting lost in translation about the tire shape.

 

[Holeshot]

I will say that I did forget about the idea that lean angle increases the effective steering angle.

As does COG.

 

[rcgldr]

assume the steeper tire is the same height and width, just steeper for moderate to high lean angles.

To clarify what I think you mean by steeper, consider the old Dunlop K81 tire which was close to a parabolic profile, versus a circular profile. When leaned over the contact patch is closer to the sidewall and further away from the center on the K81 than it would be on the circular tire, but the contact patch with respect to the path of the bike and with respect to the front tire contact patch path remains (nearly) the same, so that means the rear of the frame has to move outwards in order for the contact patch be on the same path it was before. Going to a wider profile rear tire (while keeping the front tire the same) will produce the same effect.

 

[stangmx13]

visually, the newer tire is definitely steeper at the edges. so for example, instead of the edge being 45deg from horizontal, its now 60deg. the old tire never reaches 60deg. this implies that the angle of the new tire is greater for some range starting from the edge towards the center of the tire. for that range, im pretty sure the tire is effectively narrower.

its impossible to see other changes in the profile visually without more effort. so I cant give any descriptions like "circular" or "v-shaped".

 

[stangmx13]

As does COG.

wut? how do u think the CoG impacts steering angle?

 

[tzrider]

visually, the newer tire is definitely steeper at the edges. so for example, instead of the edge being 45deg from horizontal, its now 60deg. the old tire never reaches 60deg. this implies that the angle of the new tire is greater for some range starting from the edge towards the center of the tire. for that range, im pretty sure the tire is effectively narrower.

its impossible to see other changes in the profile visually without more effort. so I cant give any descriptions like "circular" or "v-shaped".

Got it. I think that has to mean the radius of the contact surface has to be larger. If that's the case, the rear of the bike would be a tiny bit higher when leaned over. It would be a little more yawed out too, though I think the difference is probably just about undetectable.

wut? how do u think the CoG impacts steering angle?

+1

 

[fortyonethirty]

I noticed that a taller rear tire leads to easier turn in. I think being taller increases the leverage the tire has to move the weight of the bike during countersteering.

 

[tzrider]

I noticed that a taller rear tire leads to easier turn in. I think being taller increases the leverage the tire has to move the weight of the bike during countersteering.

It does. It also shortens trail, which will reduced the amount of bar force required to steer.

 

[rcgldr]

steeper ... taller ...

Assuming the same tire specs, like 190/50/17, a tire with "steeper" sides, would have a "flatter" center" and "steeper" sides, sort of like a parabola. The sideways offset would be greater at smaller lean angles, but about the same at maximum lean angle. I'm not sure about the vertical offset. When leaned over onto the "steeper" sides, the contact patch size would be greater, and assuming the same tire construction, you'd have the same percentage deformation for the same cornering load, so the deformation offset would be greater, but I don't know if it would be enough for the decrease in steering angle to be noticeable.

A taller tire such as a 190/55/17, would be 10% taller than a 190/50/17 (OEM size on some bikes). If it is just a 10% "stretched" profile of the 190/50/17 tire, it would have "steeper" sides. The sideways offset would be the same, but the vertical offset would be greater. Some guys use these taller tires for track use (I'm not aware of any OEM tire size of 190/55/17, it's "track" tire as far as I know).

A wider tire such as a 200/50/17 would be 5.26% wider and 5.26% taller than a 190/50/17, and both sideways and vertical offset would be greater.

There's also the issue of flexing in the tire due to cornering loads. If a rear tire flexes more than the front, the rear end of the frame ends up further out, the frame ends up oriented more inwards, and less steering angle is needed.

Although these factors can affect steering angle with respect to a bikes frame, I don't see how it relates to "cone version of camber thrust" or counter-steering (other than reduced steering angle with respect to frame).

 

[Holeshot]

wut? how do u think the CoG impacts steering angle?

What happens when you move weight more to the inside of the corner? does that change the steering angle? How can a motorcycle negotiate the same corner with less lean angle?

 

[rcgldr]

wut? how do u think the CoG impacts steering angle?

What happens when you move weight more to the inside of the corner? does that change the steering angle? How can a motorcycle negotiate the same corner with less lean angle?

My guess is that stangmx13 was thinking of the effect of moving COG vertically with respect to the bike, such as taller tires, heavier rider, ... , (which wouldn't change lean angle), as opposed to moving the COG horizontally inwards relative to the bike, such as hanging off or other form of weight shifting, which would reduce the lean angle of the bike.

 

[Outta Control]

youtu.be/cgtmuS8WFLU

 

[jacob11379]

At CSS I was having a problem with counter steering. I figured I must do it but I never really felt myself "push" on the handlebars.

Rode a training bike that has two sets of handlebars, normal set and a fixed set. Bike di not turn very fast when hands where on the fixed bars so after that I was probably even more confused as I still never pushed on the bars but clearly knew I was counter steering.

I found out I wasnt pushing with the bar. rather than push on right handlebar to turn right I was actually pulling on left bar. and vice-versa to go the other way.

Guess im just ass backwards....

 

[Holeshot]

There's nothing wrong with that and many riders subconsciously do it. You'll find when you have a loose handlebar, it moves when you pull it, not push it...meaning, you're pulling the bar. Very common with loose bars.

Why is a pull better than a push when riding? Think that one through and your answer lies within. A pull is much less effort (friction) than a push.

 

[stangmx13]

Why is a pull better than a push when riding? Think that one through and your answer lies within. A pull is much less effort (friction) than a push.

Nope. Friction is the same in both cases and so is force required to turn the bars. It does not matter one bit if u pull, push, or do both (ignoring the other inputs)

 

[afm199]

Nope. Friction is the same in both cases and so is force required to turn the bars. It does not matter one bit if u pull, push, or do both (ignoring the other inputs)

Ergonomically it's much easier to pull than push. In a semi tuck the arms are already almost straight out, leaving a very large angle of moment. Whereas pulling decreases the angle of moment, meaning it gets easier the more you do it. I think I got the terminology correct.

When you are old and have arthritis in both shoulders, you become aware of these things.