Last month, we introduced a new countersteering concept called the “balance band,” an imaginary line connecting the outer edges of the front and rear contact patches. Depending on whether the center of mass (CoM) is within or outside of the balance band, either direct steering or countersteering causes the bike to lean and turn, respectively. This month we look at which factors determine the exact path of travel, so we can achieve more accurate and consistent lines through a corner.
FIXED FACTORS that determine a bike’s path of travel:
Tire width: The wider the tire, the more lean angle is required for a given amount of turning.
Center of Mass height: The higher the CoM, the less lean angle is required for a given amount of turning.
Balance band length: The longer the balance band (also wheelbase), the more lean angle is required for a given amount of turning.
Rake and trail: The more rake and trail, the more lean angle is required for a given amount of turning.
Tire profile: The rounder the profile, the more consistent the traction and line is at various lean angles. The more triangular the profile, the less consistent the bike’s steering is, but the more traction is available at high lean angles. At more than 45 degrees of lean angle, lateral forces become more important than up and down forces, as far as friction goes.
VARIABLE FACTORS that determine a bike’s path of travel (can be changed or otherwise affected):
Speed: The faster the speed, the wider the line.
Body position: Moving the body modifies the position of the CoM (both height and fore-to-aft). The more CoM is moved to the inside of the turn, the less lean angle is required for a given amount of turning, which is partly why road racers hang off in turns.
Body weight and height: Heavy, tall riders can move the CoM easily with even small movements, whereas short, light riders are inherently limited in how much they can move the CoM. This is a bigger challenge for short-armed riders.
Steering speed: By pushing forward (not down) quickly, the bike’s trail decreases, which temporarily reduces stability. The sooner the bike is in balance after steering input, and back to direct steering, the better. This allows the bike to accelerate in as stable a state as possible on corner exit.
Timing: Effective timing of body position and steering movements will minimize the time the bike remains vulnerable when leaned over and unstable. There are many good advanced riding schools to help riders work on the variable factors described above. A better understanding of how both fixed and variable factors interact with the balance band will make any rider an effective countersteering connoisseur.
Lee Parks (MCN editor ‘95-’00) is author of Total Control: Performance Street Riding and proprietor of Total Control Training.