Sapper69

Hi all. While surfing the web for parts to upgrade one of my road bikes recently, I noticed some articles and videos from bike fitters talking about shorter crank lengths. While I'm 5'6", I've always used 170mm cranks (I'm in my early 50s now) and never had any problems with them. Fortunately I've never had any lower limb or hip injuries, although I have had some other serious injuries, so I'm conscious of keeping myself in good shape for as long as I can. The sizing charts based on this newer material all recommend 165mm cranks for my height and inseam, so this is something I'm considering. 'On paper' recommendations are one thing; but I'm curious to hear about the experiences of others as to any real world benefits after switching to shorter crank lengths in terms of injury prevention? Thanks!

rsbob 

Interesting question. I have no experience here but would think if you are not rocking in the saddle longer cranks would provide better leverage, but we’ll leave it up to the experts.

Fredo76

I haven't felt much difference between 170s and 175s, so I expect my first pair of 165s (bought to cure a toe overlap) won't feel all that different either. But I'll report back if that's not the case!

It might be because of my long legs, too. (26" frames or eq.)

BlazingPedals

Short cranks aren't a magical cure against damage, regardless of what the proponents may say. Those who benefit most from short cranks are the ones who already have some sort of damage. The best way to avoid damage is to spin.

epnnf

I got shorter (from 175 to 170) not because Im older (68yo), but b/c Im shorter (6' to 5'11"). We all get shorter as we grow older. YMMV

Garthr

There have been riders on shorter cranks for performance reasons since they've bee around. I started riding 150mm cranks with a mid-foot position some ten years ago or so, I can't remember exactly. I'm 74" tall with 36.5" floor to crotch bone and my largest foot measures 11-7/8 inches, a size 14. I'm at this point as riding up to 185mm cranks didn't equate to better use of what power I do have. Theory is one thing, riding is another. I often hear "longer cranks = more leverage" repeated but that doesn't make sense to me in practice, actually riding. I've also moved my saddle much more forward, about 40mm from where it once was. Just because you're "however you identify yourself" doesn't mean short cranks can't work for you, and I have no physical limitations. This just feels right for me. The best way I describe what I experience I found in this article : https://biketestreviews.com/cranklength/

Some parts that I related to ..
Really though you gotta read the whole article to get the context.

Iride01 

If you aren't having issues, then there probably isn't any point in switching. If you are a slow cadence rider at the moment and want to regularly spin a faster cadence as a norm, then shorter cranks might help you achieve that sooner. Spinning faster cadences also frequently improves speed even though you are using lower gearing .

My leg measurements would have me on > 190 mm cranks. But I'm still very happy on 165mm cranks. I didn't care for the 172.5 mm cranks I tried for 4 or 5 months. All my previous bikes were old bikes and for whatever reason just came with short cranks in the 165mm range. So my legs are just to use to them.

You may not care for the 165mm if you were to try them now. Or you might find you like them. Though a good crankset can be an expensive change just to try something out. But if your knees start giving you issues with the range of motion on the longer cranks, then maybe you should try shorter.

Just remember the saddle goes up by about whatever the difference is between new and old crank length. But for 5mm difference in saddle height, you'll probably only notice it if you ride at very hard efforts for most of your ride.

50PlusCycling

Honestly, I have never noticed any real difference. I have bikes with crank arms ranging from 165mm to 175mm, and ride them interchangeably. There aren’t any noticeable differences in how my legs feel, or in power output.

Steve B.

If you have knee issues, maybe. I’m late 60’s, knees are good so am not switching. I use 172.5 on the road bikes, 175 on the mt bikes and my gravel bike, which is used mostly on asphalt. I have never had pain from changing crank length.

70sSanO

I used 170mm cranks for many years. When I started to ride mountain bikes, too late in life, the cranks were 175mm. I do think I can spin the 170’s easier than 175’s.

I found an NOS FC-6503 for a good price. They are 172.5mm. At first I thought they may not have been a good choice, but 8 years and counting, they have been fine and I don’t even notice any difference.

While not big proponent of KOPS, I tend to error on further back than too far forward. For me that seems to have worked out for my hips and knees over the years, than the 5mm difference in crank arm length.

John

Sapper69

Thank you. Yes, this is the same sort of material I've been reading. In my mind, I held onto the "longer cranks = better leverage for climbing" logic, when in fact as this article points out, it's the leverage of the entire drive train that counts.

Wildwood 

Yes, shorter. 165/170 on any bike that has gotten a crank overhaul on the vintage bikes - which have been 175.

Without any hard evidence - I maintain when the going gets tough, spinning smaller circles is easier than bigger circles.

Alan K

Has your height decreased, as it happens to some people? But even in those cases where height has decreased, a bigger portion of it is from the torso via some compression of discs in your vertebrae. If your current crank length is still comfortable, I would keep using it. But if you are experiencing any discomfort, I would suggest consulting someone who can do proper measurements to fit bicycle to your current needs and posture. You may require some other minor changes in reach, position of saddle etc. to adjust to your current postures. As one ages, usually finding the best position to bicycle involves more than changing just one thing. [I am 70 years old and no longer enjoy leaning forward as much as I did in my younger days.]

Velo Mule

I've used some other logical arguments for shorter cranks, or more correctly right sized cranks (and that means longer cranks for riders with longer legs). But let me try this: Back when all American engines were all basically the same (pushrods), displacement was important. Bigger engine meant more power. Now, we can get powerful engines with not so big displacement. Those smaller displacement engines make power by being able to rev higher. Remember, Torque x rpm = Horsepower (or watts if you are talking about cycling nowadays).

While a longer lever means more torque, spinning faster means more horsepower (until you can't spin anymore). For a BMX start, a long cranks might be just the thing, for endurance, a shorter crank may yield better results.

I am 5'- 10" about average for a male and therefore should be just right for the standard 170mm crank that bike makers put on just about every bike that would fit me. I never questioned it until recently. I changed to 165mm cranks and immediately felt an improvement. I know, it could be the placebo effect. The key thing for me was I did not stop pedaling as often with the longer cranks, I kept going. It was a bit of a new experience to me. I didn't feel tired after an hour of riding. And my knees didn't hurt.

I used to bicycle race when I was in college. When I started, without any training, I did good. I got serious and started training and got slower and slower. My knees hurt, but that was just part of getting serious, right? Turns out, no, I had a problem. I quit racing and even limited my recreational rides.

Now, I'm not saying I'm cured by a 5mm change in crank length. I am saying that my knees have problems that I am sensitive to and these 5mm shorter cranks seem to help me.

If you are pushing a standard or long crank and it's working for you, keep going. If you are experiencing any issues or even want to try to spin more to get more watts, give shorter cranks a try. And let us know how it goes.

Speedskater

If leg Range of Motion has decreased for Orthopedic reasons or age, then shorter cranks might help.

easyupbug 

I was 5'-11" when drafted and now at 73 5'-9" but no meaningful change in saddle height however dropping to 165 cranks from 172.5 is moving through my more modern bikes and my vintage bikes are only ridden on short rides.

JohnDThompson 

I run 165mm cranks on my fixed gear bikes, for cornering clearance and easier spinning. 170mm cranks on my other bikes.

I put 155mm cranks on my wife's bike when I converted it from 700C to 650B wheels.

Sierra_rider

Here's an interesting video on the topic. It's not your average "Youtube bike fitter" vid that just talks about hip angles, this goes further and graphs angles as well as femur velocities, in relation to different crank length. Basically, the rate of acceleration of the femur, through the pedal stroke, increases with longer crank arms. The creator of the video posits that this is more taxing on joints as well as fast twitch muscle fibers. An argument could be made that both of those issues are of increased importance to older riders. Although, the ideal velocity and rate of acceleration of the femur, might not be the same for different femur lengths. I myself feel best on 172.5 or 175mm cranks, and can easily spin a 90-100 rpm cadence on them.

Trakhak

In what way does, e.g., a 165-mm crank feel inferior to those crank lengths for you?

Sierra_rider

Nothing scientific about my explanation, but longer cranks just feel more "natural." The short cranks feel like I just can't get the same force into the pedal, yet I don't see an improved cadence with them. I've never thrown my power meter pedals on that particular bike, so it's not like I have real-world data to back up my perception. I've got long femurs, so I think the longer cranks work better with my body geometry...not necessarily because of leverage differences between different crank lengths.

My road bikes all have 172.5 or 175 cranks, and I'm not sure I can tell a difference between them. My 2 MTBs are the "extremes" for me. One has 165mm cranks, the other has 175mm cranks. My perception is that I'm not using my preferred range of motion on the 165 bike and that it hurts the force I can put into them. It's not a huge difference and if I cared more, I'd do back-to-back comparisons with my power meter pedals.

Sapper69

Makes sense. I'm more of a slow-twitch guy, which is part of what makes me think I might get some benefit from 165mm vs 170. Although it was a long time ago, I originally came to road cycling from a competitive bmx background, where I was using 175mm and and bmx is all about fast-twitch obviously. Going down to 170mm for road seemed 'about right' and the last time I had a professional bike fit 15ish years ago I got a head nod from the fitter. Hadn't put much if any more thought into it than that until recently.

SharpByCoop 

I'll just share I am 5'6" and have a 30" inseam. MUCH of my riding is on Zwift. Measurable.

Indoor trainer bike: I modified a pair of spare arms from 175mm to 155mm (Drilling and tapping) on the basis of many videos on YT exploring this, and my own realization: I'm SHORT.

I could not be more pleased with the result. I found immediately less rocking butt movement on the seat, and they allowed me to spin in a circle.

For the same given heart rate I was up at least 5 watts average.

I have a gaggle if vintage Schwinns and others; I can't convert them, yet I wish I could. Works for me.

If you have a opportunity to experiment try it. The LH/RH taps are only $15 on Amazon.

Coop

friday1970

I just put 165mm cranks on a recent 1984 Nishiki Prestige to 27" to 650B conversion. I can tell the difference between my 170mm and 165mm cranks. I can tell I am turning smaller circles. But I can tell me knees like it a little more, though they don't hardly feel anything with 170's either

Calsun

Many mountain and road bike riders have been moving to shorter cranks and gaining in pedaling efficiency. I am of the school that it might help and you can always go back to the original cranks if it does not. First hand experience is always better than the advice of a self appointed "expert".

79pmooney

I've lost an inch but my pelvis to floor hasn't changed more than a mm or two. I wear the same pant sizes I've worn the past 55 years. Ride the same cranks (175) that I raced 47 years ago. I have felt a twinge now and again in my hip but is that fixable with crank length or just the result of being 70 or having crashed on both sides several timesover the years?

My knees do not like crank length change at all (chondromalacia patellae) and I have 6 bikes, all riders, so changing crank length is a big deal.