Moto GP cornering on a bicycle

[stackie]

The thread on Moto GP brought this question to my mind. Recently someone posted a pic of Rossi cornering his bike and highlighted the fact that he hung his body off the bike to the inside of the corner, allowing the bike to remain more upright through the corner than if he simply leaned the bike with his body in plane with the bike. I inferred from this that one should seek to emulate this on a bicycle.

However, I find that I cannot do this. I've never seen a pro cyclist do this either. I presume that it is different than a Moto GP bike because the momentum of a Moto GP is orders of magnitude greater than that of a bicycle simply due to mass and speed.

OTOH, I find that I can best get my bicycle around a corner by doing exactly the opposite of what Rossi does. I.e., leaning the bike more than the rider. This seems easy and intuitive, just put pressure on the inside side of the handlebar and a slight lean and the bike carves the corner very nicely. I presume this is easier since in my bicycle model, the human body is the greater moment of inertia, weighing roughly 10 times the bicycle.

Now, I'm sure that if I were to go back to my college physics book, and spend a great deal of time thinking, I could work all of this out. But, frankly, I'm lazy and am guessing that one of the genii on the forum has done so already. I hoping that one of these will feel generous on my feeble and lazy mind and comment.

Thanks,

Jon

[fierte_poser]

Do you think you would have a different opinion if your saddle wasn't in the way of you getting your body to the inside?

Also, I'm not sure your argument makes sense...if a motorcycle weighs, say 3x a rider, then that combo should be _less_ sensitive to where the rider weight is at, as compared to a bicycle + rider combo, where the rider is 10x the bicycle mass.

I think it can be said with confidence that leaning your bike while keeping your body upright is a bad way to corner.

The physics to back that up would be something like:

For a given angular velocity and radius, you want to concentrate the available mass (your arse) at the inside of the corner, so as to reduce the linear velocity of that mass, thus reducing the tangential force needed to maintain the centripal acceleration of that mass on the given arc.

The tangential force is supplied by the tire contacting the road surface, and there's only so much available before it gives up.

The further out the mass is, the greater its linear velocity and, hence, its linear momentum, and the greater the force that is required to keep it on its angular path.

I omega squared and what not.

Someone else clean those last 3 paragraphs up for me. RPS?

:beer:

[frenk]

The problem is that on a fast track corner with a motorbike you are already on the edge of the tire, so you need to hang out your body to keep the trajectory with even more speed.
If you reached the side limit of the tire with a bicycle then it would make sense, but I've never seen anyobdy lean 60 degrees on a bicycle ;)

[benb]

I've done the knee dragging thing at the track.

It doesn't feel all that different then sticking your knee out on a bicycle.

Everyone is different but the instruction I received is not too move your butt *too* much on the motorcycle. If you look at someone like Rossi he is only moving his but about 6" to the side. (You will see lesser riders at lower levels move their butt completely off the seat). It is also really interesting to watch him because he moves differently on every corner, and he is so fast despite sometimes doing things in ways most riders would think are not fast. (e.x. he always seems to use the clutch every time he shifts, and IIRC he uses all his fingers on the front brake, which is what safety schools teach but so many people don't want to do at the race track) He is really amazing to watch.

You lean the bike and not your body on a motorcycle at very very low speeds. That is a good technique for turning a bicycle in the minimum radius as well. (e.x. useful for MTB)

I don't get what you would have trouble with on a bicycle doing either.. if you lean your body into the turn (again most useful in MTB) you don't really move your butt.. just stick your knee out and bend at the waist a little in the direction of the turn.

Motorcycles are pretty darn sensitive.. yes you can move a lot further then on a bicycle.. but they don't react a whole lot different then a bicycle.

[Nathanrtaylor]

I get nowhere near as much body movement on the bicycle as I do on my motorcycle through turns, but body position does impact cornering traction a lot on both.

Through fast turns that require a lot of lean angle, I shift my upper body towards the inside of the turn. On a motorcycle they call that "kissing the inside mirror". This is in addition to weighting the outside pedal.

Doing this does decrease the lean angle you have to carry through the turn at the same speed.

[bzbvh5]

It's quite easy to lean to one side of your bicycle and go around a turn. It does allow you to go around a turn faster on the down hill sharp turns for sure. You just can't pedal and do it, it's a coasting activity. Kenny Roberts (Motor cycle racer) was the person to think to do it first.

The down side is that your road bike wheels and tires are not made to handle the side forces exerted on them while you do it. I popped a spoke right out of the nipple doing so. I would think if I leaned hard enough I could bend the rim or pull a Joseba Beloki and rip the tire off the wheel.

[djg21]

The thread on Moto GP brought this question to my mind. Recently someone posted a pic of Rossi cornering his bike and highlighted the fact that he hung his body off the bike to the inside of the corner, allowing the bike to remain more upright through the corner than if he simply leaned the bike with his body in plane with the bike. I inferred from this that one should seek to emulate this on a bicycle.

However, I find that I cannot do this. I've never seen a pro cyclist do this either. I presume that it is different than a Moto GP bike because the momentum of a Moto GP is orders of magnitude greater than that of a bicycle simply due to mass and speed.

OTOH, I find that I can best get my bicycle around a corner by doing exactly the opposite of what Rossi does. I.e., leaning the bike more than the rider. This seems easy and intuitive, just put pressure on the inside side of the handlebar and a slight lean and the bike carves the corner very nicely. I presume this is easier since in my bicycle model, the human body is the greater moment of inertia, weighing roughly 10 times the bicycle.

Now, I'm sure that if I were to go back to my college physics book, and spend a great deal of time thinking, I could work all of this out. But, frankly, I'm lazy and am guessing that one of the genii on the forum has done so already. I hoping that one of these will feel generous on my feeble and lazy mind and comment.

Thanks,

Jon

You are countersteering (pressuring bars and turning front wheel away from turn). You most definitely can steer (turning front wheel towards turn) a bike through a corner. Shift to the inside in your seat and move your body to the inside of the bike, so the bike stays as upright as possible. This allows you to pedal through a turn without catching a crank, and it works really well in wet or slick conditions where you want constant forward pressure on the rear tire in the event it starts to slip. It also works well in crits to avoid having to jump out of every turn.

[rinconryder]

I think the difference is that a motorcycle when it is leaned over, wants to stand back up again due to the drive at the rear tire, thus a rider is virtually pulling the motorcycle down with him, fighting it from standing straight up - thus the always disastrous "high side." when cornering on a bicycle however, there is no "drive" to speak of - there is merely coasting and I don't believe the natural tendency is for the bicycle to want to stand up - I could be totally wrong here though.

[Nathanrtaylor]

High sides on motorcycles are caused by totally different forces than the motorcycle wanting to stand up through a turn. They are caused by a loss of traction on the rear wheel followed by a sudden gain in traction.

ie, over-apply the rear brake while leaned over, start to slide the rear out, then fully release the rear brake. The bike will realign the tires in a quick hurry and the forces required to do it will throw the bike to the outside of the turn.

Low sides, on the other hand, are a loss of rear wheel traction followed by no gain in traction. ie, you slide, then keep sliding.

You can do both of these on a bicycle. The forces required to generate a low-side or a high-side are the same for both, just different amounts.

@bzbvh5: I'm glad I've never broken a nipple leaning through turns, but you are probably right. My bicycle wheels aren't a single structure of cast aluminum. I don't think I've been going nearly fast enough to generate the forces required to tear off a tire or break a brass nipple... though now I wonder how fast that would be.

[benb]

Not all motorcycles stand up when leaned over.

That has a lot to do with their geometry and the shape of the tire... MC tires vary in shape far far more then bicycle tires do. Cruisers tend to want to stand up, sportbikes do not.

I have some overly sporty tires on my VFR.. (bad choice) they really don't stand up much at all. They have a triangular profile. Kind of squirrely when straight up, then they want to flop over to maximum lean angle and stay there. Great for the track, annoying for most road riding.

High sides have nothing to do with the bike wanting to stand up either.. it has to do with loss of traction while cornering hard followed by abruptly gaining traction. It is the same thing that causes the wheel of your car to jerk when you regain traction from a slide.

It is apparently exceedingly rare, but possible to high side a bicycle. Usually on a motorcycle it happens because someone got too happy on the throttle at a healthy lean angle, spun up the rear tire, and then abruptly closed the throttle. The correct thing to do in that situation is to hold the throttle steady and either ride out the slide or allow yourself to crash in a lowside which tends to not hurt much if you're doing this in a controlled environment where it belongs.

[Bob Ross]

he hung his body off the bike to the inside of the corner, allowing the bike to remain more upright through the corner than if he simply leaned the bike with his body in plane with the bike. ...snip...
However, I find that I cannot do this. I've never seen a pro cyclist do this either. ...snip...
OTOH, I find that I can best get my bicycle around a corner by doing exactly the opposite of what Rossi does. I.e., leaning the bike more than the rider.

I know almost nothing about the physics or the practicality of one method versus the other, but I will point out that in a cycling skills class I took two years ago we were shown both ways, and so I find myself using both techniques regularly. Not sure if anything in particular motivates me to choose one method over the other (other than those few times when I'm consciously aware of how I took one corner and so tell myself "Hmm, I'll try taking this next corner the other way just to mix it up.")

[benb]

I think you just need to look for it, it should not be hard to see racers moving their body weight around. I've certainly seen lots of it.

Especially easy to see in MTB or Cross racing. MTBers climb all over the bike..

[toaster]

I really don't know the answer but I would investigate the fact that the motorcycle outweighs the rider in the first case instead of the rider weighing more than the bicycle in the second case.

[Charles M]

Lots of Physics blah blah...


But bicycle versus Moto lean requires no more further comment beyond traction...



Road bicycle tires don't allow lean angles any place near good street motorcycle tire lean angles. Even great street Moto tires don't have the traction to allow the angles you see in Motorcycle road racing.


You can talk about weighting pegs and saddle and moving around... No amount of moving around or handling skill will allow a road bicycle the lean angle of a heated track motorcycle.


With that, there's no reason to lean off a road bike in any sort of fashion resembling Moto racing...

[mosca]

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