Curious if others have, or are considering, going to shorter crank arms. After reading recent several articles on crank arm length I thought I'd try dropping from 175 to 172.5 mm cranks on one of my bikes. I like it!
Lennard Zinn (Velo News, frame builder, component designer, long time racer) has written quite a bit about crank arm length. Here's one link but a quick web search for Lennard and crank arm length will provide much more reading...
NoCoGreg wrote:Curious if others have, or are considering, going to shorter crank arms. After reading recent several articles on crank arm length I thought I'd try dropping from 175 to 172.5 mm cranks on one of my bikes. I like it!
Thanks for starting this thread.
I think another variable might be an individual's muscles - fiber type, where the tendons are attached to the bones, etc. I've done a lot of cycling and rowing and in both I'm somewhat faster and much more comfortable exerting a higher force at a lower cadence.
Proper crank length is both a function of femur length and personal preference as to spin/cadence/power/comfort. I'm 5' 10" and have had crank lengths from 170mm to 175mm, for road bikes I prefer 170 and a spin, for SS mtn bikes (back in the day) everyone used 175mm and you were kicked to the curb for using anything less. That was also the days of 26" tyres, and so.........we've come a long way since then.
Its very fair to say, as Lennard Zinn said, perhaps best....its a loaded issue and no easy answers
Overall: I have given alot of thought to it, and read alot about fit and given the power meters we now have, the analysis at the end of the day seems to be, you don't really gain power with a longer crank length nor do you really lose power w/a shorter one. You really have to go to outliers to lose/gain and reality is, nobody really does....nobody uses 155-160 and nobody uses 190-200
The caveat to this is the track riders: as their needs are so much different and they do use short ones, which is why recently this question has come up, and its been rumblings in the pro ranks too
mosinglespeeder wrote: You really have to go to outliers to lose/gain and reality is, nobody really does....nobody uses 155-160 and nobody uses 190-200
My wife is 5’0” with short legs. I read the studies, and we switched her to 155s(maybe 150s?). She is more comfortable and climbs better than she did with 165s.
The standard range of 165-175 is roughly a 7% range. The range in human body sizes is much more than that.
I used 182-185mm cranks for 20+ years and loved it, until the arthritis in my knee (from ACL reconstruction 40 years ago) started limiting my range of motion. Now using 175-180 (I have 8+ bikes). Took a few months to adjust. OK now.
I can tell that 175s hurt my mangled knees (5 surgeries) but can't tell the difference between 172.5 and 170 until I try to clip in and miss.
I ride 170s on my fat bike that pulls double duty as my mtb. It helps with snow/obstacle clearance and let's me lower my center of gravity which is good on ice.
Volsung wrote:I can tell that 175s hurt my mangled knees (5 surgeries) but can't tell the difference between 172.5 and 170 until I try to clip in and miss.
I hear you, I've had 6 knee surgeries (2 & 4). But I'm OK with 175 mm cranks, maybe my 35" inseam helps. According to Zinn I should be using 190 or 195 mm cranks but I'm sure that would be the end of my poor knees.
I'm tall with short legs (1.88m with 87cm inseam - 6'2 / 34"), always used 175mm because that's what came in the bikes my size. I'm building a new bike (hopefully will be my only bike), should I try 172.5? I don't have any knee problems, and would like to keep it this way.
I got my bad knees from rowing, which from how far I moved on the slide is like cycling with 280 mm cranks. I'm guessing a 2.5 mm change wouldn't have that much effect.
I ride large bikes and have to swap out cranks each new one I get. If you're building new it's a great time to test it out. In my area new take off parts and used parts sell like artisan tacos to white millennials.
I've been running a Rotor Aldhu 24 155mm crankset w/oval chainrings for several years. I have a neurological foot drop condition where I cannot pull up with my RT foot at all. I got the idea from an old Steve Hogg bike fitting article he wrote about a fit he did for someone with the same condition. Oval chainrings help me thru the (extra) dead spot in my pedaling. I also have my SPD cleats set as far back as I can although it's not quite the midfoot position that you hear about. I am happy with the setup but I can tell you that I needed to go with a smaller chainring to give me some lower gears. I definitely shift more often than when I was running 170's. It's easier to stay on top of a gear with longer cranks when you have slight variations in elevation.
I became a little obsessed with this one time and bought longer crankarms because I have long legs. i've now used everything from 165mm to 190. Unless there is an underlying issue, none of them made me faster or slower. I currently have 165s on my road and gravel bike and my tri bike has a 170 on the right and 165 on the left. I would be surprised if most people could tell the difference in 2.5 mm in a blind test. I prefer to spin and all my bikes have aerobars, so I really like the 165s.
I have a road bike and a gravel bike setup with 172. For decades I've been riding 175's on everything (road, gravel, mountain, tandem). What I've found is I'm definitely not missing the extra 2.5mm. So no I wouldn't hesitate to setup another bike with 172's.
