User Guide

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BONTRAGER WHEELWORKS
Not just a collection of specs
Bontrager Wheelworks wheels set a new
standard in wheel performance. Bontrager
Wheelworks wheels are light, fast, and rock
solid, with a unique set of application-specific
features.
Since different types of riding place
different demands on wheels, Bontrager
Wheelworks applies the features to each
wheelset which will optimize its performance
for that use. In other words, each wheelset
draws on the best specific set of the following
possible features: paired spoking, OSB (Offset
Spoke Bed), front-or-rear specific rims, disc-
specific rims, top quality spokes (aero in
some applications), and special hub designs.
Engineered wheels
Bontrager Wheelworks wheels are highly
engineered; every aspect of wheel perfor-
mance has been considered, and redesigned
when necessary. An extensive battery of tests
has proven these to be truly outstanding
products in aerodynamics, low moment of
inertia, and durability. Since we proudly list
the weights, it’s easy to see the Bontrager
advantage in this parameter. But with Keith
Bontrager, durability is always a characteris-
tic of paramount importance. These wheels
are no exception. The battery of tests which
every Bontrager wheel design must pass is
truly astonishing.
As an example, one torture test involves
placing a load on a wheel simulating a
300 pound rider on their bike, and rolling
the wheel over fixed cleats at 30 MPH.
Don’t try this at home! While all Bontrager
Wheelworks wheel designs must pass this
test, it regularly destroys many of the
wheels of our competitors.
The key to durable wheels
The most important aspect of wheel build-
ing is achieving even spoke tension, within
a range of acceptable tension. Certainly
some of the responsibility here lies on
the careful hand-finishing applied to all
Bontrager Wheelworks wheels. But even the
best trained hands won’t achieve consistent,
even spoke tension if the wheel isn’t designed
properly.
Design review
When engineering wheels, every aspect of
the wheel and its components must be con-
sidered as a group. Rim design effects lateral
and radial stiffness, spoke bed strength, and
in extreme cases impact resistance. Spokes
must be selected with the right strength and
elasticity. Hub design must provide support
for the spoke head, and flange width effects
lateral stability. All the features must match
up exactly to optimize the design’s strength-
to-weight ratio. The wheel is only as strong
as its weakest link.
The missing factor
On any bike, the rear wheel sees more
stress than the front wheel. The rear wheel
supports a greater percentage of the rider’s
weight. It must accommodate the freewheel
or cassette, yet center the rim over the axle
ends. It is trapped between the rigid chain-
stays, while some of the force that might
otherwise load the front wheel is absorbed
by the natural flex of the fork and its ability
to pivot about the steering axis. Comparing
the forces that occur in riding between the
front and rear wheels, the rear wheel can see
greatly increased radial and side loading.
Over the years, many approaches have
been taken to increase rear wheel strength.
Rather than attempt to review all those here,
we’ll simply present the goal of the Bontrager
rear wheel; create the best possible balance
of spoke tension from the drive side to the
non-drive side of the rear wheel. Bontrager
engineers closely studied the effects of vari-
ous bracing angles and carefully maximized
the distribution of the pulling load over more
spokes to reduce varia-
tion in spoke tension.
As we have said before,
the greatest source of
wheel failure is uneven
spoke tensions. Since
the inherent design of
a multi-speed rear
wheel creates a large
difference in tension
between left and right
sides of the wheel, the
best way to create a
durable structure is to
minimize this differ-
ence. If a spoke is at
lower tension than its
neighbors and the rim
is further loaded, the
spoke is in danger of
reaching zero tension.
5.6° 4.2°
Fig. W1