Brad Hubbard said:Sheldon Brown said:If you want go to with indexing, you'll also need to replace the shifters.
Pardon my ignorance but what's indexing?
TIA,
Brad
Dear Brad,
See "indexed shifting" here, which has a link leading to
"friction shifting":
http://www.sheldonbrown.com/gloss_i-l.html#index
Briefly, older bicycles often shifted by a lever on the down
tube, whose cable heaves the rear derailleur back and forth
as much as the cable is pulled. Friction on the lever kept
things where you moved them, while springs moved things
back.
These friction shifters are not a great deal more
complicated than pulling on a string until the chain moves
to where you want. They can, of course, be mounted in other
places.
The advantage is that friction shifters are cheap and
simple.
Newer bicycles have more complicated brake levers that
double as click-shifters. You pull back on the brake levers
to brake, but nudge them sideways to shift up (or down, I
forget which) a single indexed step at a time, much like
pulling a trigger repeatedly. Another lever next to the
brake is nudged to shift the other way in steps.
Shimano and Campagnolo make different versions of these
indexed shifters, but they work roughly the same way from
the rider's point of view. Fierce debates rage about the
relative merits of the two brands. Almost all touring bikes
now come with these indexed shifters.
The advantage is that indexed shifters when set up properly
let you click-click-click to whatever gear you please
without fiddling and fussing to get the chain to sit
properly, all without taking your hands off the handlebars,
which allows you to shift while heaving madly in a full
sprint.
(Or so I hear. The number of posts here about misbehaving
indexed shifters are comforting to Luddites like me.)
In automobile terms, the older friction shifters somewhat
resemble a normal car's manual gearshift, which requires you
to take one hand off the steering wheel to move the
gearshift into place, as opposed to a high-tech racing gear
shift, which consists of buttons on the steering wheel
pressed repeatedly to shift up or down.
There are times when I suspect that the widespread
enthusiasm on rec.bicycles.tech for fixed-gear bicycles (a
single speed with no freewheel that must be pedalled
whenever it moves) is a Luddite reaction to the increasing
complexity of bicycle gearing.
Another gearing option is the internal gear-hub, such as the
Rohloff, which offers a wide range of gears hidden inside a
chubby hub. While expensive and heavy, these are said to
have many advantages, including the ability to shift in an
indexed fashion while not moving.
Carl Fogel
