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9.5 Terminology


This article is from the Bicycles FAQ, by Mike Iglesias with numerous contributions by others.

9.5 Terminology

From: David Keppel <pardo@cs.washington.edu>,
Charles Tryon <bilbo@bisco.kodak.com>

Ashtabula Crank
A one-piece crank -- the crank arm starts on one side of the
bike, bends to go through the bottom bracket, and bends
again on the other side to go down to the other pedal.
Typically heavy, cheap, and robust. See ``cottered crank''
and ``cotterless crank''. Ashtabula is the name of the
original manufacturer, I think.

Biopace Chainring

Chainrings that are more oval rather than round. The idea was
to redistribute the forces of pedaling to different points as your
feet go around, due to the fact that there are "dead spots" in the
stroke. The concensus is pretty much that they work ok for
novices, but get in the way for more experienced riders.

Cassette Freewheel

A cassette freewheel is used with a freehub. The part of
a normal freewheel that contains the pawls that transfer
chain motion to the wheel (or allows the wheel to spin
while the chain doesn't move) is part of the wheel hub.
The cassette is the cogs, usually held together with small


A cleat attaches to the bottom of a cycling shoe. Older style
cleats have a slot that fits over the back of the pedal,
and in conjunction with toe clips and straps, hold your foot
on the pedal. New "clipless" pedals have a specially designed
cleat that locks into the pedal, sometimes with some ability
to move side-to-side so as not to stress knees.

Cottered Crank
A three-piece crank with two arms and an axle. The arms
each have a hole that fits over the end of the axle and a
second hole that runs tangential to the first. The crank
axle has a tangential notch at each end. A *cotter* is a
tapered and rounded bar of metal that is inserted in the
tangential hole in the crank arm and presses against the
tangential notch in the crank axle. The cotter is held in
place by a nut screwed on at the thin end of the cotter.
Ideally, the cotter is removed with a special tool. Often,
however, it is removed by banging on it with a hammer. If
you do the latter (gads!) be sure (a) to unscrew the nut
until the end of the cotter is nearly flush, but leave it on
so that it will straighten the threads when you unscrew it
farther and (b) brace the other side of the crank with
something very solid (the weight of the bike should be
resting on that `something') so that the force of the
banging is not transmitted through the bottom bracket

Cotterless Crank
A three-piece crank with two arms and an axle. Currently
(1991) the most common kind of crank. The crank axle has
tapered square ends, the crank arms have mating tapered
square ends. The crank arm is pressed on and the taper
ensures a snug fit. The crank arm is drawn on and held in
place with either nuts (low cost, ``nutted'' cotterless
cranks) or with bolts. A special tool is required to remove
a cotterless crank.

Crank Axle
The axle about which the crank arms and pedals revolve. May
be integrated with the cranks (Ashtabula) or a separate
piece (cottered and cotterless).

Also called a ``mudguard''. Looked down upon by tweak
cyclists, but used widely in the Pacific Northwest and many
non-US parts of the world. Helps keep the rider cleaner and
drier. Compare to ``rooster tail''.

Frame Table
A big strong table that Will Not Flex and which has anchors
at critical places -- dropouts, bottom bracket, seat, head.
It also has places to attach accurate measuring instruments
like dial gauges, scratch needles, etc. The frame is clamped
to the table and out-of-line parts are yielded into alignment.

A bicycle with one large wheel and one small wheel. The
commonest are large front/small rear. A small number are
small front/large rear. See ``ordinary'' or
``penny-farthing'' and contrast to ``safety''.

Hyperglide Freewheel

Freewheel cogs with small "ramps" cut into the sides of the cogs
which tend to pull the chain more quickly to the next larger cog
when shifting.

See ``penny-farthing''.

An old-fashioned ``high wheeler'' bicycle with a large
(60", 150cm) front wheel and a much smaller rear wheel, the
rider sits astride the front wheel and the pedals are
connected directly to the front wheel like on many
children's tricycles. Also called ``ordinary'', and
distinguished from either a small front/large rear high
wheeler or a ``safety'' bicycle.

Rooster Tail
A spray of water flung off the back wheel as the bicycle
rolls through water. Particularly pronounced on bikes
without fenders. See also ``fender''.

Named after the ``Rover Safety'' bicycle, the contemporary
layout of equal-sized wheels with rear chain drive. Compare
to ``ordinary''.

See ``crank axle''.

Three-Piece Crank
A cottered or cotterless crank; compare to Ashtabula.


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