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Hub Selection Guidelines
The hub is the
central point of the wheel structure where
all dynamic
loads transfer from the tire-wheel system
through the spokes into the bicycle frame.
The hub handles tremendous static and dynamic
loads created by the road, the rider, and
the tension
of the spokes. The following guidelines
should help you pick the best hub for your
application.
1) Hub Weight: Of
all the components on a wheel the hub plays
the smallest
roll on rotating inertia because it is located
as close to the center of rotation as possible.
This means that the weight of the hub is
not as significant as the weight of other
wheel components
located further from the center of rotation
(i.e. rim, nipples, tires, or tube). On
bicycles with suspension, the weight of the
hub contributes
to unsprung mass. These systems will
always benefit from decreasing hub weight. On
road bicycles decreasing
hub weight will effect ride quality and steering
characteristics, however, these effects are
usually small within a limited range of hub
weights. Decreasing
hub weight on a road bike will make your
bike lighter and this can be an important
factor for
racing or climbing where every gram can help
performance.
2) HubFlange: The
largest load on a hub is created by the tension
of the spokes. Wheels that are laced with
2, 3 or 4-cross spoke patterns create much
less
stress on a hub flange than those that are
radially laced. This has to do with
the extreme angle (or lack thereof) in which
the spokes apply
load to the flange. Radially laced
spokes patterns can contribute to flange
cracking and
breakage. For this reason many hub manufacturers
will not warranty hubs that have been radially
laced. Several manufacturers produce
hubs with extra thick or forged flanges with
holes
drilled closer to the axle, leaving extra
material to handle the additional stress
of radial
lacing. Other manufacturers design
their hubs to for use with straight pull
spokes, which
apply loads differently to the hub flange. Good
examples of these hubs can be found on some
Mavic and Zipp Wheels. Keep
in mind that larger flange diameters usually
contribute to higher lateral
and torsional wheel stiffness. For
these reasons large flange hubs are popular
with track
racers. Lower flange hubs contribute
to lower rotating inertia, which we discussed
in
the previous paragraph.
3) Other Hub Considerations: Before
selecting your hub you may want to consider
compatibility with your rim.Some hubs
are not available in very low or very high
spoke counts. For
example if you want to use a Zipp 202 hub
on your 32 hole front Mavic wheel you will
find
no such hub exists. Pay careful attention
to the number of spokes you select on your
hub and rim. Hub
width selection can be another item that
can haunt you. Most front hubs
are 100mm wide with some exceptions for mountain
bikes. Rear hubs can vary from 120mm to 160mm,
however the most common sizes are 130mm for
road and 135mm for mountain bikes. Make
sure you select the hub that applies to your
application.
Selecting the wrong hub can create a real
challenge after the wheel is built. Other
items to consider are; color, manufacturer
preference, durability in wet weather,
ease of maintenance, availability of spare
parts, and cost. |
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