Labyrinth SealLabyrinth seals work very well as long as the bearing assembly is not immersed.
The illustration shows a standard hub, but similar seals are used on some other bearing applications as well.
Since hardly anybody rides in a skirt anymore, this inferior design is pretty-much obsolete. Conventional diamond frames have several advantages over the Victorian lady's bicycle. They are:
Laprade SeatpostThis has been done by encumbering fork ends with extra hardware, ridges or lumps that keep the wheel sort-of attached even if it has been installed by someone who doesn't know what he or she is doing. Unfortunately, this means that the quick-release mechanism must be re-adjusted each time it is used, seriously slowing down the operation.
Since this extra stuff was installed as a defense against frivolous lawsuits by ambulance-chasing shysters, the extra bumps are sometimes known as "lawyer lips" or "lawyer tabs."
As "lawyer lips" have become the norm, they have gradually become more important than they originally were, for two reasons:
See my Article on Quick Release Skewers.
Left-threaded fasteners are turned counter-clockwise to tighten them.
Left threads are found on left pedals, some bottom-bracket parts, and internal parts of freewheels.
Left side pedals, and right side bottom bracket cups use left-and threading because of the phenomenon called "precession." It is somewhat counter intuitive, because the direction of rotation caused by the precession is opposite the (much smaller) torque exerted by bearing friction.
See the Pedals entry in this Glossary , and Jobst Brandt's article on Left Hand Threads on this site for a detailed explanation of precession.
Spoke nipples and the expander bolts that hold bar-con shifters in place often appear to have left threads, because they are approached from the opposite direction of most fasteners.
See my article on Derailer Adjustment for more details.
Lock nuts are used to secure bearing adjustment of most hubs, headsets, pedals and sidepull brakes. Most hubs use lock nuts to secure the cones so that they will stay in adjustment. These lock nuts are the outermost parts which are screwed onto the axle, and their outer surfaces press against the insides of the fork ends of the frame. The lock nuts are therefore the reference point by which axle width and dishing are measured.
| English/ISO | 1.29" x 24 TPI |
| Campagnolo/Phil Wood | 1.32" x 24 TPI |
| Old French | 33 mm x 1.0 mm |
Lock WasherThreadlockers are mainly used for threads that are not intended to be fully tightened: adjustment screws and the like.
There are very few good applications for threadlockers in bicycle work. They include:
If these are overtightened, they can "mushroom" the ends of the cantilever bosses, causing the brake to bind up.
French and Italian fixed cups are threaded in the wrong direction, so there is a tendency for them to loosen up in use.
Low gears make the pedals easy to push, but you need to turn them faster to get the bike to move at a good speed.
Low gears are achieved by using small chainwheels and large rear sprockets.
Low gears are used for climbing hills, or for starting up from a stop.
Up until the late 1950s, all spring loaded derailers were low-normal type. When Campagnolo introduced the parallelogram-type rear derailer, they changed to high-normal, and most rear derailers made since then have been of the high-normal type.
The major advantage of high-normal rear derailers is that, when used with a low-normal front, both levers move in the same direction for double shifts. This makes it easier to perform a double shift with down-tube shift levers.
The major advantage of low-normal derailers is that they generally downshift a bit better than high-normal units.
Since the late 1990s, Shimano has attempted to revive the low-normal rear derailer design, using the trademark "RapidRise." This has met with increasing acceptance by cyclists.
Sun Tour used to make high-normal front derailers. The principal advantage of this was that the front and rear shift levers moved in the same direction to either raise or lower the gear, which was less confusing for beginner cyclists.
As mountain bikes became popular in the 1980s, the heel clearance issue became a serious problem, because mountain bikes generally used smaller frames than traditional designs. This put the seat stays lower, and the problem of the riders' heels banging into the ends of the brake cantilevers became a real concern.
The industry responded with a re-designed cantilever where the arms were angled up higher, and didn't stick out so far to the side. This fixed the heel clearance problem, but introduced problems of its own.
With low profile cantilevers, the mechanical advange decreases as the brake shoe moves inward toward the rim. This is an undesirable characteristic, and causes the braking performance to deteriorate sharply as the pads wear down.
See also my article on Cantilever Geometry.
Most newer cranks use the "low profile" design, where the bottom bracket is made shorter, and the crank runs outward at an angle from bottom bracket to pedal. This gives improved heel clearance for riders who tend to pedal splay footed.
Note: The fact that a crank is "low profile" says nothing about its tread width (a.k.a. "Q factor.") In fact most "low profile" cranks have fairly wide tread, but this has nothing to do with the "low profile design.
The trend toward wider tread resulted from the wider chainstays introduced with mountain bikes, and also the additional clearance required to keep the right crank from rubbing against the cage of the front derailer (newer front derailers optimized for triple chainwheels require more crank clearance than older front derailers did.)
Some frames use internal lugs, with a necked-down section that fits inside of the tube, rather than having a socket that the tube fits into.
L.W.B. A Linear LWB recumbent |
Lycra is also sometimes used as a covering for plastic/foam saddles, but it is rather fragile for this application.
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