#1 : Crank Length for big and tall cyclists
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April 5th, 2009
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Zinn's Big and Tall Bike Shop
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Zinn Cycles Big and Tall Newsletter
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 is devoted to crank length, which is one of most important aspects of proper bike fit. If you know someone else who may benefit from this newsletter, please use the forward email link at the bottom.
Thanks, Lennard Zinn
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Big and Tall Cycling topic #1: Crank Length
I'm
excited that you're reading the premier edition of the Zinn Cycles
quarterly Big and Tall Newsletter. While this is a big and tall
newsletter, it is our intention to keep it short. I'll be choosing a
topic applicable to tall cyclists in each edition, so feel free to
suggest topics for future newsletters. This issue is devoted to
long (and short) cranks. As you know, we almost single-handedly have
been producing cranks outside of the stock 165mm-180mm size range
available from large crank makers, and you may be one of the many
satisfied customers pedaling with them. Crank length is too long a
subject to cover completely in a short newsletter. I constantly get a
lot of questions about it, and sometimes I sound to myself a bit like a
broken record. So here you'll find answers to the most frequently asked
questions, and soon we'll post answers to many other FAQ's on the
subject on the crank pages of zinncycles.com.
Why do you make cranks over such a wide range of sizes? Because people range so much in size! When
I first got into riding seriously, I got the longest cranks I could
(180mm), because it made sense to me that with my 6'6" height I should
have the biggest frame, widest handlebar, longest stem and longest
crank available. That logic after all held true with clothing, beds,
cars, etc., so why not with bikes? Later, when I got my first
really nice racing bike, a Masi equipped with 177.5mm cranks, I noticed
that when I switched those cranks to 180mm, I immediately started
dropping the guys I'd been climbing evenly with. The next year (1980),
when I was first on US National Cycling Team and was having my bike fit
checked, Edward Borysewicz ("Eddie B."), the US head coach at the time,
told me I needed considerably longer cranks yet. My quest for cranks
longer than 180mm began then and never stopped until I could offer
proportional-length cranks for tall (and short) people. Little kids'
bikes have small wheels and short cranks as well as small frames, stems
and handlebars because it works best that way. A small child is so
inefficient as a rider that he or she cannot get the bike going if it
is not close to optimally efficient for them in terms of sizing.
Remember that, besides being new to balancing on a bike, a kid's bike
is much heavier relative to their weight than your is to your weight. As
the child grows, kids' bikes available to them have increasingly longer
cranks and larger wheels, as well as bigger frames, stems and
handlebars. Given that, doesn't it seem a bit strange that when we
become adults our bikes all have the same wheel size and essentially
the same crank length? Are we all suddenly optimally suited to the same
crank length and wheel size? Nobody questions that there needs to be a
wide range of frame sizes, stem lengths, and handlebar widths to fit
everybody. However, you can count on your riding buddies and bike shop
salespeople questioning it if you want to ride a crank outside of the
given 5mm range from 170-175mm. Many of the standards in the bike
industry are based on traditions that started pre-WWII (even pre-WWI)
when people, at least in first-world countries, were smaller on average
than they are now. And it also stands to reason that the last thing
crank manufacturers, distributors, and bike shops want is the expense
in tooling and inventory of as many crank sizes as there are bike frame
sizes (or shoe sizes!).
How do you determine crank length? For
most road riding, we recommend a length between 21% and 21.6% of a
rider's inseam. (Inseam is measured in bare feet from the ground up to
the top of a level broomstick pulled up firmly into the crotch.) This
is based on seven years of experience of selling custom cranks. A
shorter length is often called for on a mountain bike and a cyclocross
bike (see below). For most track events, a shorter crank is also
advisable.
What about pedal clearance in corners? Clearance
depends on the crank, the frame, the pedals, the rider's technique, and
the type of event/ride. In the ideal situation, the frame is built to
fit both the rider and the crank for the type of riding they do; then
the bottom bracket height can be adjusted to provide the desired pedal
clearance. At Zinn Cycles, we generally build the bottom bracket on a
frame getting a 200mm crank 25mm (one inch) higher than the BB of a
frame made for 175s. However, the majority of our crank customers
are not putting their Zinn cranks on frames we or another custom
builder has made to fit them. The longest crank we recommend for
somebody using a stock frame is 200mm, and only if they are not even
thinking of racing criteriums. In a criterium, more power is worthless
if you open a gap to the next rider in every corner that you have to
close at great expenditure of energy because you had to restart
pedaling later to avoid hitting your pedals on the road. I think it
inadvisable to race criteriums on a stock bike with a standard (265mm)
bottom-bracket height using any longer than a 175mm or 180mm crank. We
do have successful tall masters racers competing on our cranks up to
195mm who must use a stock frame due to sponsor constraints. But they
adjust their riding style and choice of events accordingly. For
anybody who has a question about whether they'll have enough pedaling
clearance if they buy a crank from us, we recommend taping a styrofoam
block the thickness of the length difference they are considering to
the bottom of their pedals and notice if or when they touch it to the
road.
Do long cranks hurt cause knee pain? Our
customers without a history of pedaling-related knee pain using cranks
in the 21-21.6% of inseam length range almost universally report no new
knee pain with the longer cranks. We are choosing a length that is in
keeping with the length that champion cyclists use relative to their
leg length, so your knee and hip angles will be no tighter than theirs,
and your percentage of extension and flexion of your muscles will also
be no greater. So mechanically, there is no reason you'd have more knee
pain. Lower cadence is often associated with knee pain, but that is
without changing crank length. If you pedal at a lower cadence but have
more leverage, the peak load can be the same. If you pull a stuck nail
out of a board with short claw hammer, you feel more strain in your arm
than if you pull it out using the claw on the end of a long crowbar.
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NEW: Terra 5.0
The Terra 5.0 is our titanium all mountain machine. The titanium frame
is light, strong, and absorbs any jolt that gets past the suspension.
The Terra climbs like a cross country bike, and handles the most
challenging descents around. Titanium can flex under load, so it can
take big hits much better than other frame materials. The Terra is
designed for custom cranks and 29" wheels, so, when combined with
Lennard Zinn's Project Big custom frame design, this bike is the
ultimate all mountain bike for big & tall riders. The Terra can be
set up with S&S couplers for easy travel, and is dubbed the Terra
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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.
I also created my 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.
Sincerely,
Lennard Zinn President and Founder
Zinn Cycles |
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