FOUR > TECHNICAL INFORMATION
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for the amount of brake lever pressure required for each wheel at
different speeds and on different surfaces. To better understand
this, experiment a little by walking your bike and applying different
amounts of pressure to each brake lever, until the wheel locks.
When you apply one or both brakes, the bike begins to slow, but
your body wants to continue at the speed at which it was going.
This causes a transfer of weight to the front wheel (or, under heavy
braking, around the front wheel hub, which could send you flying over
the handlebars).
Besides learning about the braking pressure “threshold” – the point
in which squeezing the brake levers causes wheel lockup, it is
important to learn how the transfer of body weight plays a crucial role
in safe and effective stopping or slowing down. A wheel with more
weight on it will accept greater brake pressure before lockup; a wheel
with less weight will lock up with less brake pressure. So, as you
apply brakes and your weight is transferred forward, you need to shift
your body toward the rear of the bike, to transfer weight back on to
the rear wheel and at the same time, you need to both decrease rear
braking and increase front braking force. This is even more important
on descents, because descents shift weight forward.
Two keys to effective speed control and safe stopping are controlling
wheel lockup and weight transfer. This weight transfer is even more
pronounced with having a front suspension fork on your OHM
bicycle. Front suspension “dips” or “travels” under braking, increasing
the weight transfer (see Section 4.6). Practice braking and weight
transfer techniques where there is no traffic or other hazards and
distractions.
Everything changes when you ride on loose surfaces or in wet
weather. Tire adhesion is reduced, so the wheels have less cornering
and braking traction and can lock up with less brake force. Moisture
or dirt on the brake discs reduces their ability to grip. To maintain
control on loose or wet surfaces it is wise to go more slowly.
CAUTION: The motor in the rear wheel also becomes a
generator when using the rear brake. Please note that the
generative mode does not replace the existing brakes, but
increases considerably the braking quality and will help you
slow down when needed. It activates as soon as the rear brake
lever is activated.(see Section 4.9)
4.4 SHIFTING GEARS
Your bicycle has a combination of a derailleur drivetrain and a variable
power assist drive system. (For power assist details, see Section 4.9)
HOW A DERAILLEUR DRIVETRAIN WORKS
The gear-changing mechanism on your OHM bicycle includes:
• Two shifters on the handlebar (XU450 urban has single twist grip
shifter only)
• Front derailleur (XS700 sport only)
• Rear derailleur
• Rear freewheel sprocket cluster
• One or Three chainrings
• Drivetrain
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