Greetings!
We're
glad to present another edition of the Zinn Cycles quarterly Big and
Tall Newsletter. I'll be choosing a topic applicable to tall cyclists
in each edition, so feel free to suggest topics for future newsletters.
This issue talks about 29er wheel strength for big and tall riders. We get many inquiries about how bigger guys should choose wheels. This article goes into wheel strength in factory and custom built wheels. It also discusses proper rims, hubs, spokes, and nipples to use. The next newsletter will discuss road bike wheel strength for big and tall cyclists.
Thank you,
Lennard Zinn
President
Zinn Cycles Inc.
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29er Wheel Strength for Big and Tall riders
As
essentially all of our mountain bikes for years have been 29ers, and as the
vast majority of our customers are taller than 6'4" and well over 200 pounds,
we at Zinn Cycles have a lot of experience with 29er wheels for big riders.
The
quality of the build is critical, and the rim, spokes and spoke count must be
chosen appropriately for the rider. Due to availability, prior to 2006 or so
we only used 24mm-wide road trekking rims of around 550 grams, namely Mavic
A719 and DT Swiss TK7.1, and we only built 36-hole wheels for big riders.
However, those rims were insufficient for 6'8", 250+-pound North Shore riders who
had problems with pinch flats on such narrow rims, as the available tires only
had thin, cross-country casings. For these riders, we use Kris Holm
Unicycle.com rims, which are 38mm wide and around 900 grams, reducing pinch
flats and wheel failures, even off of big drops with big riders. There are also now some other in between options for all-mountain 29er rims.
While higher
spoke tension makes the wheel neither stronger nor laterally stiffer, it is
usually necessary with larger rider size to avoid so much deformation of the
wheel while rolling that the bottom spoke becomes completely de-tensioned,
leading to nipple loosening and rim and spoke fatigue. The lifetime of the
wheel is higher with more uniform spoke tension, and a professional
wheelbuilder with a lot of experience can give you that.
While
I believe that you can trust most of the name-brand pre-built wheels to be safe,
most of them will have too much lateral flex for a big rider to be able to
sprint confidently or steer precisely on sharp downhill turns at speed. Fatigue
will also be an issue; the rim will develop small cracks at each spoke hole on
the rear wheel, often just after the 6-month warranty has expired, and spokes
may break as well. This is a common problem we have seen from bigger riders before we set them up on a custom built wheel.
I
believe that a big rider with an aggressive riding style ought to not buy
factory pre-built 29er wheels at this stage in their development. In 26ers, there's
a wide range of pre-built wheels made for downhill, freeride, and all-mountain,
but most pre-built 29er wheels are made for cross country, which won't cut it
for a big dude.
For big
riders, I recommend through-axle hubs in both the front and rear. 20mm, 9mm, or QR15 up front and 10mm or 12mm in the rear. The nice thing about the 10mm through axle, is that it can be used on a standard quick release dropout. The 10mm axle fills the entire space of the dropout providing much better dropout support. Both ends
will track better by virtue of the stiff axles tying the fork legs and swingarm
members together, and the rear through-axle will prevent the hogging out of the
right rear dropout that can happen with a big, strong rider under high torque
in low gear. You will know about this if you cannot keep your rear wheel from
pulling over to the left chainstay, no matter how tight you keep your
quick-release skewer.
Secondly,
I would recommend high spoke counts - at least 32, and preferably 36, with high-quality,
double-butted 2.0/1.8mm (14/15-gauge) stainless steel spokes with (brass)
thread-locked nipples to prevent them from loosening up (we use DT Competition
spokes with DT Pro Lock nipples). The stretchier, double-butted spokes make for
a longer-lasting wheel than would straight-gauge 2.0mm (14-gauge) spokes of the
same quality. As the spokes stretch, they move some stress concentration from
the weakest points at the elbow and nipple, and the nipples stay in contact
with the rim under high wheel deformations (often occurring under somebody big),
reducing rim fatigue.
The
Mavic A719 has been replaced by the TN719 disc-brake specific rim, and the DT
TK7.1d is also a disc-brake version; these rims are narrower than I think is
ideal for 250+-pound riders, but they are plenty strong if built up well with
36 spokes and through-axle hubs and make for a light, fast wheel for riders
under 250 pounds. For aggressive riders over 220 pounds, I would recommend 27-30mm-wide
all-mountain rims, like Halo Freedom 29, Sun Ringl� MTX 29 (585-gram) or Equalizer 29 (540-gram),
or, for riders over 250 pounds or for getting air, Kris Holm 34mm-wide rims are the best option.
For
pre-built wheels, if the rider is under 200 pounds, and especially if running
tubeless tires, the Mavic C29SSMax is a great wheel and is available with a
front through-axle. For riders over 200 pounds, I'd recommend the Sun Ringl� Charger 29 with the 20mm through-axle option. It has the narrower and lighter (27mm,
490-gram) Equalizer 27 rim and 32 spokes, but it should still hold up very well
as long as you're not doing a lot of hucking.
Follow
Lennard on Twitter at www.twitter.com/lennardzinn
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About Us
For more than a quarter of a
century, we at Zinn Cycles have been working to make cycling more
enjoyable for our customers, and that commitment remains at the heart
of everything we do. We express it by building bikes that fit great,
perform well, and are thoroughly thought-out for their owners' needs.
And it does not stop with the frames; our cranks and our forks are
specifically designed for our customers, and the components we select
and how we set them up are tailored for them as well.
Lennard
Zinn also created his books and maintenance DVDs out of that same
commitment to empower the reader or watcher to be more comfortable with
their bike, which then attracts us to ride more. We each can only do so
much to save the world; fortunately cycling is something we all share
that is good for the earth as well as for us both in the moment and in
the long term.
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Zinn custom magnesium track bikes will redefine what you've thought
about riding the track. Our track frames are so stiff, that it feels
like you are riding on a rail. The unique vibration damping of
magnesium absorbs any vibration or jolt and keeps you in control of
your bike at very high speeds. Our custom extruded bi-ovalized tubing
provide for a very aerodynamic track frame, which means you will go
faster and be in more control. Zinn project big track bikes are fully
custom and designed for zinn custom long cranks. Your bike will be made
with appropriate bottom bracket height to accommodate whatever length
crank you choose and according to your local track's rules.
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Zinn photo gallery on Flickr
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Zinn's Big and Tall Bike Shop: SALE!
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