This is so misleading and only true in certain situations. I hear it all the time and have been taught this before by very good riders. However, it completely ignores the fact that the bike will turn significantly better when the front forks are compressed (and that speed has a direct bearing on turning radius). Physics! You cannot get a bike to turn at a track pace WITHOUT being on the front brakes. How about that? This is one of Freddie Spencer's main principals.
...
On the street, if you have to tighten your line (reduce your turning radius) you can do one of two things: lean the bike more (reducing your contact patch) or slow down. The best option in any one situation depends on many factors.
I respectfully disagree that my comment is "misleading." To dismiss it as wholly "misleading" is to ignore, indeed, the physics of the situation. I was brief, perhaps too brief, in my post which may have led to, what felt like a whole-hearted dismissal of the notion or point I was making, and so here we go...
As has been pointed out, there is some physics involved in this equation. And I'm no engineer, nor authority on physics, so I fully expect to have someone step in a clarify or educate me/us on the details.
As I understand it, and will explain it to my students (I'm a cycling coach, downhill and cross-country my specialities), there are [probably, at least] two forces at work when a two wheel vehicle is put into a turn. Centrifugal and centripetal.
The centrifugal force is the one most folks understand -- it's the force that makes it feel as if you're going to be flung off to the outside of the turn, if you're not leaned into the turn. And it's a force that will definitely greet you if you do not lean/counter-steer the bike.
I challenge anyone to go out and get on a bicycle, pedal in a straight line and try to execute a turn by literally
turning the handlebar in the desired direction without a conscious lean. From my experience, it can't be done. Please wear a helmet...and capture it on video, too. We can also demonstrate my initial point of "standing up the bike" during such an exercise. Ride at a reasonable rate of speed, not too fast, and turn your bike. As you turn the bike apply your front brake and let me know what the bike does. I know from experience that it will stand up. Because we're denying it the use of centripetal force and, instead, compelling it to allow centrifugal force to exert or express itself more fully.
The centripetal force is the one that's present/working to accelerate the vehicle through the curve; the force that's pulling the vehicle toward the center of the turn. (here's where there's a gap in my understanding and thus an ability [or willingness] to attempt what I would feel to be an accurate or precise definition of this force. So you're getting my layman's understanding.) There's something to do with Newton's second law of motion involved in this equation. How the force, the dynamic tension, of the vehicle being expressed down, through the tires (contact patch) toward the outside of the curve/turn and the presence of centripetal force, cause the vehicle to accelerate out of the turn.
If one has the ability to hold the line and hit the turn apex spot-on and consistently, then one's speed will increase as the combination of momentum and centripetal force does it's thing when you go through the turn (hit the apex). This, in addition to the expert tuning of their vehicles, is, I think, a contributing factor to how folks on the track are able to achieve and sustain such high rates of speed. And perhaps yet another reason why we shouldn't try to ride at track speeds on the road. A track is a relatively controlled environment, public roads are not. But that's another thread...
I definitely won't dispute the notion that a motorcycle is optimally poised to realize it's best, fullest speed potential when the suspension is in its "sweet spot" wherein it is partially compressed. We want the vehicle to be attempting to "extend itself" as we move through the turn.
If we brake hard as we go into a turn we'll cause the suspension to compress and we'll lose a whole bunch of energy and momentum through this unwanted action; we'll dissipate a whole bunch of energy straight into the suspension, energy that could have been used to maintain and, perhaps, gain speed. That's why it's important to get most of one's braking done before entering the turn and then attentuate one's speed, very subtly, with the front brake (trail brake) as the bike is leaned in. But that's really sorta beyond the scope of the initial question, or at least it's an advanced understanding/concept/practice that a really new rider may not do well.
Indeed, being smooth is, to my little brain, of the surest ways to get to and sustain high rates of speed.
zzzzzzzzzzzipping up the nomex suit...
