When you are riding down a straight line (such as on the rode) on a
bike, and you turn right, must the rear tire of the bike cross the line to its
left, or does it never veer to the left? Thanks.
There is no reason why the rear tire should veer to the left, but
it can if you are making a hard right turn and want to get started
on the turn from further out into the road (tighter turns are harder).
I would have to reply that the rear tire must move left -- but
probably not enough to measure very well. When riding in a straight line you
are(presumably) balanced over the tires. If you turn your front tire to the
right to turn to the right you are immediately thrown off-balance and
off of the bike. In order to make a right turn you must adjust your
center of mass to be to the right of the wheels by turning slightly to the
left and then back to the right. The tightness of the turn must
be matched to how far you lean the bike.
Any time you are turning a bike you are essentially falling. Turning
your handlebars into the direction of the fall causes the net force on
you center of mass to change from downward to be toward where your
wheels contact the road.
Experienced cyclists (and not much experience is needed!) do not notice
that they are actually turning to the left just before a right turn
because they are continually adjusting their wheels to correct their
balance. When they want to make a right turn they just stop correcting
(for falls to the right) until they have started turning.
gregory r bradburn
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Update: June 2012