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zinn big and tall bicycles
#1 : Crank Length for big and tall cyclists April 5th, 2009
IN THIS ISSUE
Crank Length
Zinn's Big and Tall Bike Shop
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Zinn Cycles Big and Tall Newsletter
 
lennard zinn 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


 
custom zinn tegrated cranks
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.



terra 5.0 titanium full suspension bike 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 World.
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