I remember that well, it was part of the way they justified his performances.
From what I remember, before he popularized the high cadence, people liked to grind up hills in a hard gears. I don’t like doing that unless I’m out of the saddle. Maybe it is better to think about foot speed vs cadence? With the longer cranks the cadence and foot speed feel more balanced.
Thanks for sharing this, I’m really excited to try this out and see how it compares to RAD
I feel like crank length along with a lot of other measurements are best established by bike fitters, it’s really their realm.
Which got me thinking, @Daniel_Y do you think you could recruit a pro fitter or two to join the forum? Perhaps Isaac and Victoria from Befitting Bicycles?
It’s a good suggestion. I don’t know any fitters personally, maybe others can help out!
I work with arguably the best fitter in Australia. Multiple national title holder on the track and road and is the go to fitter for all the para athletes. I’ll ask him and see if he’s interested in sticking his head in here.
Really interesting. I have long legs (90cm/35" inseam) for a person of my height (183cm/6’-0"). Just measured my tibia at 45cm/17.5".So both calcs have me at 175mm cranks which what comes standard on large bikes so it’s all I’ve ever run. Go figure.
Is there any study that mentions single speed riding. I ride SS MTB pretty much exclusively these days and can’t really imagine shorter cranks would be of any benefit there?
One of them looked at standing pedaling and found that shorter cranks (don’t remember how much shorter) were better.
Keep in mind that you have to change your gearing on a SS if you change your crank length.
-Walt
I feel like some people here are missing the point a bit. I’m not saying your existing cranks are a bad or that you should slap 145mm cranks on all your bikes.
I’m saying that there are design opportunities that are untapped if you have the option of using shorter cranks for certain types of bike, and that this (like different wheel sizes for different types/sizes of bike) is a potential area for meaningful improvement.
-Walt
Been on 160mm cranks on two different hard tails for a year. 165mm cranks on my commuting / touring bike for two years.
Never been more comfortable on a bike ever. I can’t run long cranks because of a knee injury. The wider spinning circle aggravates my knee badly, especially if I’m putting power into the cranks.
Mounting 160mm cranks on my hardtails made an immediate difference. I changed from 170mm. I ride in a mountainous area with lots of rocks. I never crank strike anymore and when accelerating uphill I don’t loose rear traction any more.
Shorter cranks with short chain stays (420mm on one of my current HTs) made it so the back wheel spins out less. Maybe this is from the change of leverage (170 to 160) and how much faster I can accelerate on 160s.
I feel that long crank lengths is a road bike holdover and they aren’t really best suited for MTB. Whenever I bring up crank lengths with roadies they always believe they need more leverage but they can’t even run their 50 / 11 ratio.
Hardtail Party has a good 30 minute video about crank lengths on youtube. Was a big inspiration for me to pick up a couple pairs. It isn’t very scientific, mostly just on ride feel.
For reference I’m 5’7", with a 30" in-seam.
Using the 41% metric for tibia length? That would be 185mm unless I’m missing something.
Hmm. I guess the calculator max’s out at 175mm regardless of the inputs. Probably because Appleman doesn’t sell cranks longer that that. Honestly I’m not curious about longer cranks as I think that would create ground clearance implication for trail riding. And it sounds like I’d lose performance based on the research linked so far in this discussion.
This is interesting. My intuition would be that longer cranks are better for mashing but I been wrong (many times) before. Since I have 7 bikes with 175mm cranks I’m in no rush to swap over as that would be very inefficient on my wallet haha. And my SS hardtail also has a 320mm BB height so I’m not chasing ground clearance there. It sounds like geared full suss bike sounds likes where shorter cranks would have the most notable benefits. Something to consider for a future build!
This is why it’s important for people to include at least some basic bio-metric data when discussing their personal preferences. The 20% of inseam calc has you on shorter 155’s but actually put’s me on on longer 180’s haha. Nice to hear that shorter cranks are working for you!
NOTE: @Daniel_Y, this cranks length chat is great but seems to have become it’s own stream outside the general “driving dimensions” chat proceeding it. Could that make this info hard to find later?
Good suggestion, I moved it to a separate thread, hopefully no one gets too confused 
That’s a good idea moving this, felt a bit bad crowding the ‘driving dimensions’ thread.
It’s an exciting time to be wanting different length cranks because companies like Ignite Components can make custom lengths (and this is the custom frame forum after all, where we can decide BB height , where I would hope I wouldn’t need to clarify that I realize 195mm cranks on a standard height BB road bike would be problematic).
I’m totally on board with people trying short cranks and lower BBs on MTBs to improve bike handling. It would be somewhat concerning if it became a big trend where all new MTBs came with really low BBs, but now that I build my own frames 
I do think it’s important to keep an open mind on longer cranks for tall people and approach it from a position of why the hell not? It’s proportional to their bodies. The bike industry has a clear incentive not to offer longer cranks on larger frames because it requires a higher BB. Personal experience leads me to be extremely stubborn on this topic I’m afraid. For reference my tibia measured 18.5 to 19" and I’m 6’4.5" tall. Haven’t measured my inseam recently, but from memory it’s 36 or 37". I prefer handlebars level with the saddle or slightly above and don’t do aero positioning.
I did notice something last night… if you spread your feet further apart in the standing position to simulate longer cranks in the horizontal position, your head get’s lower. Lower CG anybody?? 
When citing research studies, it’s really important to keep in mind all research has flaws. I think it’s important to read between the lines to get a complete picture.
This is the most referenced crank length study:
Determinants of maximal cycling power: Crank length, pedaling rate and pedal speed
Every research study has its flaws. Just take the first sentence of the experimental method :
Trained male cyclists [n=16, mean (SD) age:29 (7) years, height: 179 (6) cm, mass: 73 (7) kg] volunteered to participate in this investigation.
There is definitely selection bias when people volunteer for studies. Most glaring, a test group of all male cyclists excludes half the population! That was normal for 2001, but would be incomplete in 2023. It also does not mention different body types or ethnicities.
Finally, I think the biggest flaw is not the study, but people’s interpretations of the result. Look at the RPMs that the experiments were conducted:
The optimal efficiency everyone cites is happening above 120RPM. No one is spinning 120RPM on a mountain bike.If you sprint out of corners at that RPM, you are way more likely to smoke a rock, even with your tiny 150mm cranks. If you are spinning a mountain bike at 120 RPM at threshold on the flats… well… you are probably a crazy person.
When you look at this chart, you look at the relationship backwards and still be correct:
When I read these crank studies, my interpretation is: AT MOST you gain or lose 5% of your maximum power output in laboratory conditions. To me, that is not enough to make a difference in the real world. So just pick whatever crank length you want.
I think the bigger performance gain is easier gearing that allows you to spin more, but that is not as sexy of a topic!
I think you’re spot on @Daniel_Y, crank length doesn’t really matter in terms of pedaling efficiency, especially for MTB.
I think the argument @anon91558591 is making is that if it doesn’t really matter, why not get some 155s, drop the BB 20mm, and see if we can make a bike that rides significantly better as a result of the lower COG. That’s a big change that should have real noticeable impact, not due to pedaling efficiency but due to overall geometry allowed by the lower BB.
(That said I’m a single speeder who swears by 180s)
Exactly. There’s design space here that could be utilized now that we know efficiency/power aren’t significantly affected by crank length.
@Daniel_Y Keep in mind that what you feel when riding is mostly foot speed, not RPM. Shorter cranks don’t require any higher footspeed. The faster cadence actually happens organically, most riders don’t even notice they’re spinning faster.
-Walt
Also, @Daniel_Y , as I said, you can find flaws in all of these studies. But there have been quite a few of them now, and the message is consistent.
I do find it a little humorous that as the old curmudgeon I’m apparently the weird radical person on this subject and all the youngsters will let me have their 175s when I pry them from their cold dead hands!
It’s hard to change your mind about something for us all, I guess.
BTW, out of curiousity, how on earth would your ethnicity affect your crank length/power output numbers?
-Walt
I think the argument would be: because it’s was never tested in a study, we can’t know.
I don’t think it’s a stretch to say that on average, different ethnicities have different heights, BMI, proportions, kinematics, and physiology. All those variables added up could easily throw off the confidence interval for their results. This could have a very similar result to the teenager study, where the added diversity gave inconclusive results. No one cites that study, because research is very biased too: only positive results get published, and you look for your articles that support your claim.
I think the shorter crank length and experimentation are great. Having more shorter options includes more people that are typically excluded (the shorties). I am just playing devil’s advocate, trying to encourage people to think critically about bike design.
Sure, but if anything, including more people who aren’t white dudes would basically mean shorter people - who would probably do better on shorter cranks. In a way the tall dudes producing the same power is more convincing.
Playing devils advocate is great but unless you’re going to go do a study of your own, you’re just sort of being stubborn, right?
If you really think the results are going to be different for Pacific Islanders or whoever that’s one thing. But I don’t think anyone really believes that, so criticizing the studies that exist on that basis just seems like a way to rationalize refusing to accept something that you really don’t want to believe.
-Walt