9 Reasons to Upgrade to Short Cranks
If you want maximal power when climbing or sprinting, there is no crank length better than 145mm. If you need more reasons to upgrade, keep reading.
Below are nine reasons why you should upgrade to short cranks.
Many of these benefits also apply to standard (legacy) bicycles, not just your Cruzbike.
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Short crank arms make the bike more aerodynamic (they actually make the RIDER more aerodynamic on the bike).
With shorter cranks, your knees don’t pop-up as far into the clean airflow, nor do your heels drop as low into clean airflow; thus reducing turbulence and drag. -
Short crank arms make fitment easier (more knee clearance).
Because your feet are making slightly smaller circles, your knees travel less and there is more room for your knees in front of the handlebar. -
Short cranks make more power (Watts).
A study performed at the University of Texas at Austin by J.C. Martin and W.W. Spirduso found that 145 mm cranks made maximal power higher or equal to longer cranks. Many people erroneously assume that longer cranks make more power because long cranks allow more torque for the same force. It’s much more complex than that. https://pubmed.ncbi.nlm.nih.gov/11417428/
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Short cranks benefit both tall and short riders.
The study above found only a weak correlation (R2 = 0.205) between taller riders with longer legs making more power with longer cranks. Even tall riders can reap benefits from short cranks.
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Improved handling while pedaling through corners, because the mass of your feet are rotating with a smaller radius.
Angular momentum at the crankset is directly related to mass (feet/shoes/pedals, etc.) but increases by the square of the radius (crank length). The difference is subtle, but you may notice a feeling of more precise control as you pedal through corners. - Shorter cranks allow higher cadence with less foot-speed, which is a biomechanical and physiologic advantage (high cadence = good, high foot-speed = bad).
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Short cranks are lighter.
They also work better with smaller, lighter chainrings. Switching to shorter cranks may require a change in your gearing because it increases the Gain Ratio (the ratio of how far the bike moves vs. how far the pedal moves). For example, switching from a 170 mm crank to a 150 mm crank has the same effect on Gain Ratio as switching from a 46T chainring to a 52T chainring. If you use a 50T chainring with 170 mm cranks, you would use a 44T chainring with 150 mm cranks to achieve approximately the same Gain Ratio. Therefore, shorter cranks use smaller, lighter chainrings. -
Short cranks are stiffer.
All crank arms flex, but given the same material and design, a shorter crank arm will flex less than a longer one. The stiffer the drivetrain, the more efficient it is (less mechanical energy loss). -
Short cranks reduce pressure at the patellofemoral joint, a common source of knee pain.
The more the knee is bent during contraction of the quadriceps, the more pressure is exerted on the cartilage behind the kneecap, which may cause pain and injury. Short cranks reduce the amount of flexion at the knee during quadriceps contraction. This is also another reason to have your boom extended as much as comfortable so that your knees are not too flexed.
Ready to switch? Check out the high quality 145mm crankset upgrade that we custom ordered here.
@John Anderson Yes, I think it does somewhat, maybe that’s part of the explanation of #5.
@Stanley Fox Your Q45 has short cranks! They are 155mm, so very close to 145mm. I wouldn’t switch those out until you wear ’em out.
@Mike Jens – which model did you get? It might have short cranks already. Some of our bikes being sold now had the components purchased during the Covid epidemic. We love our customers and want them to have the best, but there are long production pipelines that delay rollout of new components. I’m sure your Cruzbike is great as-is, but should you decide to upgrade, we have short cranks in stock.
@Stephen Christensen Yes, the Croder set will work with your SRAM rings. You will need to buy a separate spider with the SRAM 8-bolt mount and the bolt-pattern of your Powerglide rings.
For every cm you shorten your crankarms, you actually gain TWO cm of extra knee/lower thigh clearance assumimg you leave your handlebars the same distance from your body. With 1 cm shorter cranks the bottom bracket is now 1 cm further away for the same leg extension at the bottom of the downstroke and at the top of the upstroke (a gain of 1:1). Then, due to the fact that your crank is also 1 cm shorter, your pedal and thus your knee/lower thigh is an additional 1 cm further from the bars. 1+1 = 2
Years ago I went from 170 cranks to 145 on my V20 and suddenly had a luxurious amount of knee clearance. Was then able to move the bars out more and get my arms straighter. And had easier starts. Well worth doing!
Note that on a ‘legacy’ bike if you go from, say 165 to 145 cranks you’ll need to raise the saddle by 2cm. If you can’t also raise your bars by 2 cm, well…that’ll just make your upright bike even more aerodynamic….aka uncomfortable 😉
I have a 2020 S40 which has a SRAM power glide 50/34T. Will the kit work with this set up? If not, what would I need to do to utilize 145 mm crank arms? Thanks for your help.
Why didn’t I have the option of a shorter crank on my Cruzbike Q45 when I bought it at cycle loft 2 months ago?
It seems that short crank arms would decrease the force component that steers the front wheel drive bike to the side opposite power stroke. Do you notice this effect?
I just bought a new Cruzbike with standard crank arms. Now, less than one week later, you tell me there is a new crank arm that sounds much better than what you provided for the standard crank arm. It’s frustrating to see you advertising all these improvements, but not including them with the standard Cruzbike purchase. How about providing a comparison of the new crank arm to the standard version, instead of just tempting us with something that supposedly is newer and better.
Been using shorter cranks for a couple years and LOVE them. I DO feel like they’re better to climb with and I think they’re helping my wife with her knee issues since I was recently able to get her to convert from 172s to 155s.
I never thought about the aerodynamic aspects or benefits in turning for recumbent bikes, but it makes sense.
When I eventually get my S40, I’ll definitely be getting a set of these 145s. Thanks for posting this
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