User Guide

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A 23c tire with 120 PSI will exhibit more out-
of-roundness than this.
Our wheel builders use a Villum, a highly
sensitive truing stand that uses dial indica-
tors driven by precision-bearing sensors roll-
ing on the rim edges. When 0.5mm passes
by the indicators on the Villum, the needles
move about an inch. What looks like a moun-
tain on the Villum will be totally missed by
the rider, even at high tire pressures on
smooth pavement. With an egg-shaped wheel
where 0.5mm height change occurs over 1/2
of the wheel rotation, the out-of-roundness
may be invisible with a normal truing stand.
If that same 0.5mm deviation occurs in a
short rim section, it’s very visible to the
naked eye.
With Bontrager Wheelworks, the same
0.5mm vertical tolerance is allowed, but
instead of an egg shaped wheel it can show
up over a very short section of the rim. In
either case, the rider will not feel it, nor
will it effect the ride of the bike. Consider
the much greater magnitudes in the out-of-
roundness of a wheel. The tire will be out
of round by 1-2mm on a 23c tire, more as
the casing gets bigger. A rider sitting on the
bike with that same 23c tire at 110PSI will
compress the tire by another 2-3mm. And
unless your roads are a lot better than here
in Wisconsin, the road surfaces often have 5,
10, and even 20mm variation.
The “little marks” on the rims
On some 2002 and later Bontrager rims
and wheels there are small spherical indenta-
tions in the braking surface of the rim. This
isn’t a blemish, it’s a wear indicator. If the
braking surface has worn so that the indica-
tor is no longer visible, have your dealer
replace the rim.
Technical Specifications
For detailed technical specifications, wheel
building instructions, spoke lengths, ten-
sions, and hub maintenance information,
please refer to the Bontrager Wheel Service
Manual (found on Dexter), or cybersurf to
www.bontrager.com.