World-class MotoGP racers such as Ben Spies spend so much time at extreme lean angles that
Discoveries indicate our brains don’t much care from which part of our bodies they receive data in order to analyze and organize the physical world around us. For example, a blind person can "see" approaching objects from a forehead-mounted video camera that sends impulses to a tongue strip that has slightly electrified dots on it. Subjects could roughly describe the objects in view from the pulses the plate emanated. This suggests our brains can read any electrical inputs they receive and, it is theorized, route them to the sight decoding center.
Our system for sensing movement and balance has three components: visual, muscle/ joint position and an inner-ear mechanism called the vestibular system. All three are used to sense and respond to changes in our orientation to earth and things in our environment.
Among its potentials, this three-part system allows us to track both moving objects and our own movements in relation to stationary ones with accuracy. It’s like an organic accelerometer that allows for the visual tracking of objects. We would be unable to ride or walk or coordinate our movements very well if it didn’t operate like that. We’d look like birds that, without this system, must move their heads in quick, jerky motions to gain accurate references to coordinate their motion through space.
With our internal guidance, tracking and coordination systems in mind, consider one of every sport rider’s dilemmas: lean angle. What is the average rider’s sense of it? Where, on a scale of confidence from 1 to 10, would he place himself in relation to using all available lean angle?
Since we can’t ride around looking down to see how close our bikes’ hard parts are to the ground, our heroes of the past have come up with an alternate and helpful adjunct to assist: dragging our knees. That action gives us a fourth layer of data gathering. Without it, many of us are blind when it comes to lean angle. At track days, riders look at photos of themselves with great interest, trying to get a sense of how far over they arethe farther, the better, of course!
What it feels like compared to what the photos show is often quite sobering. Despite our great system of balance and orientation, we suffer from a lack of hard data while riding. Even if we could ride with heads-up displays across our helmet visors showing how far over we’re leaning, chances are it would still feel scary and weird to go over farther.
Thirteen years ago, when I discovered that my Lean-and-Slide training bike completely bypassed any fear of leaning, I was at once both delighted and terrified. Riders jumped on the bike, apparently abandoning any fear. Without a thought they took it to 45-plus degrees of lean, half again farther than many of them had ever been before. Trust in the bike’s outriggers was implicit.
Back on track on a normal bike, they showed marked but incomplete improvement. Off the practice pad, they were still gun shy of leaning over "all the way."
Truth is, no one wants to be at max lean for very long, or very often. Understanding those limits helps.
Those limits include tires, but they’re less of a problem these days; modern premium rubber displays excellent grip at extreme lean angles. The problem remains the same as before: cornering clearance and reduced suspension compliance with every degree of lean we add.
For riders, it’s a point of confidence. When you know where you are in the lean-angle game, you have an idea of how much speed/lean you may or may not be able to add in any given corner.
Although lean is not an absolute gauge of traction, it does provide the rider with an indicator of what chances he may be able to take.
For riders coming up, who don’t have enormous confidence in traction, the knee gauge offers more information to reckon with. Once riders gain a consistent feel for knee contact, and are not experiencing any side-grip problems, that indicator alone announces that they’ve still got some lean and grip in reserve. The knee is a reliable gauge of lean once you get its "telemetry" wired to your other senses.