Short Crank FAQs
What length crankarm is best for me?
Experience, and communication with hundreds of customers, has convinced me that no formula will work for finding the optimum length for a certain individual. The range of motion over which your muscles work efficiently is more of a determining factor than femur length. If you can squat down till your butt touches your achilles tendons and smoothly rise without a great deal of effort, you won't have as much to gain from shorties as someone who can't.
I've observed that everyone has a critical crank length below which their muscles or joints will work well throughout the pedal stroke. If your cranks are a little shorter than your critical length, it doesn't seem to make a lot of difference whether you are 1mm below it or 10-20mm below it.
Not all sizes are available, but there seems to be a lot of leeway. 148 or 153 may not be optimum for you. But for many recumbent riders they will feel so much better than 170 or 175 that whether they are exactly your optimum length becomes a moot point.
Taller riders have become accustomed to cranks designed for average sized riders. So, they are used to a slower rate of angular movement at their joints. They might do best with cranks somewhat shorter than any formula based on leg length would suggest.
Shorter riders also have become accustomed to cranks designed for average sized riders. So, they are used to a faster rate of angular movement at their joints. They might do best with cranks somewhat longer than any formula based on leg length would suggest.
What size chainrings should I get?
Most people with 26" drive wheels are going from 30-42-52 to 26-36-46 or 24-34-44. Faster riders are using 24-39-48. A few have gone to 22-34-42.
When I shorten Shimano 105s & Ultegras, about 1/3 of the owners have me install 24-39-48 FSA ramped and pinned rings to replace the stock 30-42-52 setup. Cost = $84
It's not unanimous, but a large majority of riders with 20" drive wheels and shorties do well with standard "Road Triple" gearing of 30-42-52.
Will I have to move my seat (or BB)?
Won't shorter cranks feel funny?
After going from 170mm to 148mm, Martha P. of New Mexico wrote;
"There was no adjustment period, not even for one second."
At bike events, I like to let other 'benters try out my bikes. I never tell them beforehand about the shorties. Dozens of times I've seen them return commenting about the handling, seat, or acceleration. But they never even notice the cranks.
Will I see a performance gain? Or loss?
You might find this VeloNews article interesting. All the riders, from 5'1" to well over 6 feet performed best on 150mm arms. What makes this really amazing is that all testing was done at 90 rpm, while shorties raise your natural spin rate.
Will these fix my knee pain?
Who should not go to short cranks?
Because you put more force on the pedals, for a given amount of muscular effort, in addition to the cartilage and meniscus problems mentioned above they could aggravate some types of foot problems.
Can I Use My Current BB Spindle?
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