- Motorcycles, Sports Bikes & Riding
Motorcycle Sportbikes: How and why to drag a knee
If you ride a sportbike on the street, it may occur to you that you're riding it to about 10% of its potential. But, on the street there is 90% more danger than on a closed course, like a bonafide racetrack. But, maybe you're one of the lucky ones that lives where the twisties are free of sand, rocks, animals, and guard rails, and you wish to increase your corner speed.
Sportbikes were made for the pure rush of running a bike as fast through a corner, sliding the front tire, and then spinning the rear out of the exit of the turn. But, without the proper Center of Gravity (CG), Contact Patch, and throttle application, then one may find themselves in a baseball-style slide on their butt, or worse, being ejected into the stratosphere due to a high-side.
Why does dragging a knee help
The first thing to understand is that the wheels are rotating masses, that result in a gyroscopic effect, and this makes the bike want to stay upright. If you've watched any motorcycle crash videos, then you've probably witnessed the "Ghost Rider", whereas the real rider has fallen off, but the bike seems to have a mind of it's own, and stand up and run from the danger like a branded horse. By moving your weight to the side of the bike of which you want to turn, it helps to overcome the forces that are actually working against you to go through the corner. Leaning into the turn is the first step of the how.
Moving your weight to the inside edge of the corner should be done in such a way that if someone where to place a yardstick across your butt cheeks, the stick would be relatively perpendicular to the wheels of the bike. Many newbs will not slide their butt left(port) or right(starboard), but rather twist at the waist causing one cheek to slide more forward on the bike, and the other more aft on the bike. Doing this twist motion would make the yardstick point more diagonally forward and aft, and makes it nearly impossible then to drag the desired knee.
So, getting yourself off the bike toward the inside of the turn with chest down, and your outside foot weighting the outside peg, will lower the CG of the entire bike and reduce the level of the gyroscopic effect.
Tire Contact Patch
Despite how great tires have become since the days of Steve McQueen, let's face it, you don't use very much of them at any given moment. When the bike is sitting still, with your weight fully on the bike is the only time when you maximize your contact patch. (except when you tie it down in the trailer.) Everything action you take with the bike from there reduces the contact patch down to less and less until it becomes the size of a postage stamp. So, when you enter a corner, the more you lean the bike, the greater the reduction of the contact patch, thus, your goal is to keep the bike as upright as possible to maximize the contact patch.
"BUT WAIT?!", you scream, "You just said the gyroscopic affect causes the bike to want to be upright, therefore I must lean it over, but if I do, I reduce my contact patch and increase my chance of crashing, and I need to keep it more upright to corner?!"
CORRECT! There is but a razor's edge between turning and crashing.
When you place your knee out, it isn't really to place any weight upon as much as it is a "curb feeler" or "lean indicator", to figure out where you are, and how much further you can go to overcome the gyroscope, but to get the bike to turn. As you enter an exit the same turn over and over again, you soon find where your knee should be. (or in the case of Ben Spies at Mid-Ohio, where your elbow should be.) Only through repetition will you achieve maximum corner speed... without touching a bar to the ground, that is.
Why did I crash, I had my knee out?
I've been in corner's where my knee is dragging and the inside of my knee is against the bike frame, and it's physically impossible to lean anymore without crashing. Other times, I've leaned and barely touched my knee, and the bike just disappeared from under me. Every corner has it's own nuances and only through repetition will you understand what your limits of traction are for that corner. And although it's good to watch others do it, cornering is like a golf swing. Everyone rides differently, so your body position, bike setup, and lean angle may work for you, but not for someone in front or behind you, and vice versa. Some guys ride dirt bike style, some lay down, some just flail and make it up as they go along.
From Average Joe to Racer Pro
If nothing else, perhaps this article will give you a greater appreciation for what the pro racers are doing on their Honda CBR, Kawasaki ZX, Ducati, or Suzuki GSXR. As they enter a corner, they're either braking early, to get a better, rear tire sliding, drive out, or they're "crashing" the front end, which means sliding the front into the corner to have more corner speed with less braking, or BOTH. Watching a MotoGP or World Superbike race at Phillips Island will give you perspective of both. Turn 1 they ride hard onto the front tire, but they spin the rear up and over Lukey Heights, turns 8-10.
Of course these guys have unlimited tire budgets, but they barely get a nickel's worth of use out of the middle of the tire. Now that you've read this, you better understand the principle's involved, and can start applying them to your next canyon ride, track day, or race.