Eight Bicycle Variables Affecting Distance To Stop means for the Bicycle Brake Stop Calculator -

  1. speed is V

  2. Gradient is G

  3. Coefficient Of Friction is f

  4. direction of road ahead (between 0 degrees and 90 degrees) is Dir

  5. bicycle/cyclist weight = Mass is M

  6. wind speed impact is W

  7. braking ability of the bicycle and rider is Ab

  8. road surface, as the rider will likely feather the brakes on bumpy sections

On a two wheeled vehicle, a rider cannot jam the brakes on for a 'full' in an emergency stop.

The rider needs to achieve weight transfer first.  This means an initial gentle application of the brake before a big squeeze.  If the rider jams on the two caliper brakes instantaneously without moving the body weigh backwards, ideally back over the seat, the front end can go out from under the rider, particularly if applying powerful hydro brakes.

Re variable 8. above, when braking heavily a rider will subconsciously ease off the brakes momentarily when crossing over bumps etc on the road surface (eg cracks, manhole covers etc). This is to stop the wheel locking as it is unweighted over the bumps.

The following is the Federal Requirement for bicycle stopping distance with a hand brake.  It is in 16 CFR 1512.5.
(1) Stopping distance. A bicycle
equipped with only handbrakes shall be
tested for stopping distance by a rider
of at least 68.1 kg (150 lb) weight in accordance
with the performance test,
1512.18(d)(2) (v) and (vi), and shall have
a stopping distance of no greater than
4.57 m (15 ft) from the actual test speed
as determined by the equivalent
ground speed specified in
1512.18(d)(2)(vi).

Nigel Waterhouse & Associates
Aeronautical Consulting Engineers