Turn in with about 100 mm of fork travel
Yamaha crew chief Tom Halverson looks for about 100 mm of fork travel at turn-in. ChampSchool shows how the front brake sets that.
3 min readBy PitPin Desk
The front brake changes the bike's shape
In this animated video, the ChampSchool coaches show what the front brake does to the chassis. When you squeeze it, the fork compresses, the shock extends, the wheelbase shortens, and rake and trail get smaller. The bike becomes quicker to turn. Roll on the throttle and it all reverses: the fork extends, rake and trail grow, and the bike wants to run wide.
The load also flattens the front tyre onto the road and makes the contact patch bigger. The coaches say that is why expert riders go to the brakes when they get nervous, and trade brake pressure for lean angle until they are happy with speed and direction.
About 100 mm of travel at turn-in
Most modern sport and sport-touring bikes have about 125 mm of front fork travel. The coaches asked Yamaha crew chief Tom Halverson whether he looks for a number at turn-in. His answer was about 100 mm.
With the fork fully extended, the rider has let go of the brake or started accelerating before turn-in. The front is unloaded, the contact patch is small, and the bike runs wide.
With the fork bottomed, the rider braked very late or abruptly. There is no travel left, the bike resists turning and runs wide. The coaches say this is where the idea that the front brake stands the bike up comes from.
At about 80 to 100 mm, the tyre profile stays round, the front is loaded and the bike turns as designed.
In hard straight-line braking before turn-in, the fork can be on the stops, and that is fine. Citing Bradley Smith, they say you then have to give up some brake pressure to get the tyre profile back before you tip in.
Where the rear brake fits
Coming into a braking zone on the throttle, the rear tyre is loaded, so a little rear brake slightly before the front slows the shock's rebound and the weight transfer. As front pressure builds, the rear unloads and you ease off the rear.
As you trail off the front and add lean, the rear reloads. At full lean you may be off the front completely, but the rear can still slow the bike and tighten the line. On the exit it helps control traction and wheelies.
The coaches also say downhill corners need more brake pressure than uphill ones.