Motocross history is filled with examples of creative ideas that sank into the swamp of forgotten technology. Do you remember
the infamous BASS System? It was Yamaha’s totally
unique and innovative brake-activated suspension system.
Designed by Yamaha’s engineers for the 1985 model
year, BASS was the Yamaha acronym for “Brake Actuated
Suspension System.” The idea had some merit on paper,
but it didn’t work on the track. A cable ran from the
rear brake pedal to the shock’s compression valving.
When the rear brake pedal was pressed, the cable
would open a valve to lighten compression damping.
Typically, when you applied the rear brakes on a
motocross bike in choppy bumps, the torque effect
between the wheel, swingarm and chain caused the
rear suspension to stiffen. As the rear suspension
locked up, it created a sensation known as wheel hop.
Yamaha’s engineers surmised that by opening a
valve in the shocks compression circuit when the rear
brake pedal was pressed, the shock damping would be
free to absorb braking bumps and lessen “Yamahop.”
The damping change was 12 percent (which was the
equivalent of six clicks out on the compression adjuster).
BASS wasn’t a total failure through braking bumps,
but, unfortunately, BASS worked any time the rear
brake pedal was pressed and would lighten the shock’s
damping on the face of jumps, in smooth corners
and when dragging the brakes through whoops.
Yamaha’s Brake Actuated Suspension System was discontinued in 1986—and the idea was forgotten. ❏
IDEAS FROM THE ASH HEAP OF MOTOCROSS HISTORY
The BASS system was operated
by a cable running from the brake
pedal to the shock’s compression
adjuster. When the brake pedal
went down, the shock’s compression damping was reduced by 12