billymtb
Likes Dirt
Physics hasn't got on holiday.
Look at your tyres. On the edges they have raised aggressive knobs and in the centre they have flattened faster rolling knobs and sometimes sharp edges for braking - they wear quickly.
Those outer knobs are also softer rubber ion many tyres because they see so little use, thus the tyres have a better coefficient of friction on the edges that don't see use when travelling straight up and down.
Second - if you are laying over naturally and the bike starts to slide enough that you slow down - you will overbalance the bike and go down to. If however, you are more vertical, and the bike starts to slide and you slow, you can lift the bike more vertical to hold balance and the natural forces at play.
Now why aren't any of these techniques used in moto? Well the bike is too heavy for the rider to handle as easy, and 2, when they slide and slow, they simply apply more power .
Yup, but my argument wasn't about lean angles are their effect on grip, although it plays a big role. I agree, a more upright position will allow for a better reaction to sliding out and thus staying in control. But this does not mean more grip! alot of websites preach that it results in more grip, but actually the correct reason is that it puts you in a position to respond to sliding out with much more efficiency.On 1 i think it's about moving your centre of gravity over the bike so when/if the tyres do lose grip then you slide and are able to gain traction again instead of going down like a bag of shit.
this is more true for slower corners where the centripetal forces are much lower, if you stay parallel to your bike, the weight that is pushing through the tyres is nearly all centripetal, and very little of it is your weight force. If you take a fast corner with your body over the bike, you have a much higher chance of flipping as your centre of gravity and pivot point has changed. Testing the body over bike position in a parking lot is very inaccurate, you are far from demonstrating the actual forces of a high speed corner. I have written alot of notes and drawn alot of diagrams about this theory, and the more i think about it, the more i am confused.I'm no physics expert, but I apply a similar principle to cornering my bike as I do to skis.
If you just lay over and stay parallel to the bike you are then unable to apply any pressure to them, and you will eventually be detracting from their traction. If you stay above them you can apply pressure therefore enhancing their ability to grip. Same with skis, keeping your body upright allows you to load up the edges with pressure far more than laying over with them, allowing real bitey cutting turns.
Saying this, I believe this applies more to shorter turns, it gives you a tighter whippier turn. Linger more drawn out corners it doesn't apply so much as you're not asking as much of your equipment.
Try riding your bike down the middle of the road slaloming the white stripes, keeping your body upright and central and kinda laying your bike out side to side, you'll feel it whip back in underneath you. Same thing with slalom skiing.
That's my take anyway.
If only life were so simple.
It is in fact quite a complex interaction between bike and rider and includes the geometry of steering, centre of mass in relation to the bike (ie height, fore-aft and lateral), reaction through the tyres, as well as the cornering forces. All whilst maintaining control..
http://www.coachcarl.com/training_articles/cornering.htm
http://genjac.com/BoomerBiker/Two Wheeled Physics.htm
Yes i know it is 3 dimensional, but the only reason i would have to look at all dimensions is if it were all dependant on one another, i have drawn alot more diagrams for this problem, and have left out alot of my calculations because it would be really hard to show on a forum. low centre of gravity vs high has a slight effect on grip, but the main difference is a lower centre of gravity provides more stability in the corner, such as a hitting a rock. The rock won't damage your course as much if your centre of gravity is low and thus aiding stabillity. In a perfect world, centre of gravity doesn't have a pronounced affect on grip and mass is still equal to m. Thats why i didn't mention it, but now i see that it will affect cornering in real life situations.You're going to need a load more physics (and maths) before you'll get anywhere close to understanding cornering on a bike. I've for a degree in mathematical physics, and know for certain that I'm not even close to having the skills/knowledge to explain all the complex systems interrelationships going on.
In relation to your points, you're forgetting to factor in the other ways in which a heavy object distant form the balance/pivot point is affecting forces in other directions. By your logic, a low vs high center of gravity would also have no effect. There's a load of friction effects to take into consideration, and everything needs to be considered the three dimensions rather than two. Get out your vector calculus book....
But doesn't braking also employ the tires to do two job in layman terms. The tire it now trying to deal with a braking force and a traction force, also braking tends to force the bike to want to stand up and not down like it should it corners, it will also shift lots of weight forward resulting in a loose rear end. we cant compare cars here because they have completely different make up of design and control. better off looking at moto gp.
Now my layman understandings because it appears they haven't been outlined for us simple none physic genius's is
1.Braking should be done before the turn, this allows proper cornering position and more speed to be carried through the corner as the tires have one job and one job only which is to grip not to slow down as well.
2.Cornering over the bike.
This concept is that the center of mass stays up right and therefore the angle in that the inertia mass is affecting the tires is very different. When you place the weight up higher the angle is less acute from the ground which puts less force on the tires to slide out. It simultaneously puts more force into the tires from above keep them planted in the ground with down ward pressure and less sideways pressure which again results in more grip and less inertia pushing the tire sideways.
2. Outside foot down.
This lowers the position of the center of gravity again, because your weight is placed on your the lower the pedal the more weight you are placing against the force applied to the inside of the tire trying to push it out.
3.Berms there is less need for these concept to be taking into account some corners you should apply them but other its not necessary and you can get away with leaning the body and just ripping the bike around the corner
4.Braking
Unweights the and essentially makes it unstable while taking pressure off the tires which reduce grip, When braking it introduces a force that wants the bike to stand up in the corner, braking employs the tire to to two jobs at one, slow down while griping.
The point of this post is to highlight my layman understanding of the concepts as I believe these are the main reasons shared by many and open up the discussion on them.