User Guide

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namics is spokes. Many Bontrager road
wheels use aero, or bladed, spokes to
reduce wind drag. These wheels
also use reduced spoke counts,
relying on PST (Paired Spoke
Technology) to maintain high
wheel strength with fewer
spokes (Fig. W4).
Front and rear road wheels
have different needs. On a bike,
the front wheel sees the most
wind resistance because it is the
leading edge of the bike. The rear
wheel is “drafting the seat tube”,
and is in much more turbulent
air. For this reason, some models
of Bontrager road front wheels
use a deeper, more aerodynamic
rim than the rear wheel.
Mountain bikes have different needs
Compared to road wheels, mountain bike
wheels place a greater need on wheel dura-
bility and rigidity. Aerodynamics are less
important. Acceleration becomes very impor-
tant, effecting your ability to change speeds,
attack short climbs, or negotiate other obsta-
cles in the trail. A Bontrager mountain bike
wheel uses alternating spokes and a lighter
rim to create a wheel with lower moment of
inertia (Fig. W4) to make acceleration easier.
Mountain bike wheels sometimes require
special configurations, like the ability to
accept a disc brake rotor. Again, Bontrager
Wheelworks mountain bike wheels select
those features which will best create the ulti-
mate structure.
With disc-specific wheels, the rim does not
need a flat sidewall. Removing this design
constraint allows optimization of the rim
shape to reduce weight. Placing a rotor on
the front wheel creates an asymmetric spoke
configuration that can be enhanced using a
rim with OSB (Offset Spoke Bed), thereby
reducing the required dishing and providing
more balanced spoke tension from left to
right side of the wheel. Also, Bontrager
disc wheels use crossed spokes to efficiently
transfer disc brake forces between the hub
and rim with less stress on the wheel.
With rim brakes, Bontrager Wheelworks
incorporate tall sidewalls so that brake
adjustment is easier, and pad wear has less
effect on proper adjustment; taller sidewalls
provide increased surface for the brake pad
to mate to.
Bontrager rear mountain wheels focus on
balancing spoke tensions on the drive and
non-drive side of the wheel. To do this, they
employ OSB (Offset Spoke Bed) rims and
special hub designs with modified flange
spacing. These features greatly reduce the
tension differentials from side to side, creat-
ing a stronger, more durable structure. The
higher left side tensions allow more torque
transfer to the left side drive spokes. In
other words, Bontrager Wheelworks moun-
tain wheels are stronger.
Truing Bontrager Wheelworks wheels
Most Bontrager wheels employ standard,
externally adjustable spoke nipples. The only
exceptions are the Bontrager Race X Lite
Carbon Road wheels, and the Bontrager Race
X Lite Aero road wheels where a small
aerodynamic benefit can make the difference
between winning and losing a race.
Bontrager Road wheels use PST (Paired
Spoke Technology) which require a slightly
different technique to true. In many respects,
truing Bontrager Wheelworks wheels with
PST is just like truing a conventionally
spoked wheel. Each spoke has both a vertical
and lateral component to its pulling force.
As you tighten a spoke, it pulls radially in
towards the hub, and laterally out towards
the hub flange.
The difference is that on a Bontrager wheel
with PST, the lateral force is directly opposed
by its ‘partner’, the spoke adjacent to it.
As the partner reacts to your tightening of
a spoke, there is no further lateral force
applied to the rim. Contrast that to a conven-
tionally spoked wheel where each spoke has
two ‘partners’. As you tighten one spoke, it
effects the tension, and thus the spatial posi-
tion, of the two partners. This in turn effects
the next outward pair, and so on.
When truing Bontrager Wheelworks road
wheels, PST sometimes gives you more con-
trol over both vertical and lateral rim devia-
tions. If the rim is slightly out of true but
very round, you can loosen one partner and
tighten the other. The rim moves laterally,
but not up or down. And since no other
spokes are directly affected, you’re done.
Vertical deviations
With wheels built in our factory, the toler-
ance allowed for vertical deviation is 0.5mm.
Fig. W4
34.7 gm
2
46.9 gm
2
Moment of inertia