jrhii

I at at the other end, 5'5 (and a half), i can't recall my inseam, but my pants length would be 28" or so if I could find a pair, and a standover of 30" in just barely works with shoes on. I have 170's but can't really afford anything else. I wander if it would help me out, I usually don't have any problems, but a slight knee ache after longer rides or if I don't position myself quite right.

Wouldn't a 165 or 160 give less leverage? would it be very noticeable?

Kimmo

Again, the only way to be sure if a given length works for you is to suck it and see.

...That didn't come out quite right

oldbobcat

Oops, 17.39 cm.

oldbobcat

The same height as Jacques Anquetil, and he used 175s. Most riders at his height used shorter cranks, though. Eddy Merckx, at a little over 6', used 175s, Greg LeMond and Lance, at 5'10", used 175s.

Being proportioned like Eddy, I use 175s. When I switched from 170s, it took some time to recover some leg speed, but my climbing improved and I felt more comfortable on my bikes. My fixie trainer has 170s for easier spinning downhill.

Kimmo

I found it really easy to get my spin back on 175s (5'10", 32")... it took maybe half an hour to get used to them.

Monster Pete

I've ridden bikes fitted with 140, 165 and 170mm cranks. I can still produce power effectively with either of them, but the 140mm set feel noticably different (the 165's are virtually identical to the 170's). If you are a fast cadence rider, turning a shorter crank with a lower gear may be easier than turning a long crank with a proportionally higher gear (same gain ratios) but I doubt you'll notice a difference. We all climb the same sized staircases and ladders without thinking about it

Medic Zero

This discussion makes me wonder- would running a longer crank help mitigate riding a frame that was a little small for you? (Effectively lower= lower saddle and lower stem?) It seems like with as little difference as folks are saying they experience I could switch from 170's to 180's and drop the stem and seat about half an inch on a frame that is a little small for me and feeling a little twitchy with a long stem and seatpost on it.

HillRider

If this thread shows anything about crank length it's that it's very subjective and there is no "formula" that fits every, or even most, riders. Some are almost indifferent to crank length changes and others are very sensitive. The only real answer is to try different lengths and see 1) does it matter and 2) if so, what length are you most comfortable with?

The only objective data available indicates the power output is very insensitive to crank length but riders perceive their comfort level differently.

531Aussie

I'm not shooting the messenger, but Gord, I wish this website would just go away and die. I don't reckon the guy (Kirby Palm) has updated his site since the web was invented, so maybe it was just a passing thought he had that he longer agrees with?! In my opinion, his formula is a complete joke, because it suggests insanely long cranks for anyone over roughly 5ft10' (very roughly). I'm just under 6ft with an 89cm (35") inside leg, and the 'formula' would have me using 192mm cranks!! I shake my head every time I work that out!!

It's based on nothing but some wild idea he had one day. He just pulled out one inseam/crank length combination to suit his theory, then applied it to all.
It seems as though he's a part-time inventor with some 'interesting' ideas:
https://www.nettally.com/palmk/index.html

When justifying his formula, he starts with a couple of general and reasonable comments:
"Taller people should use longer cranks." Fair enough.
"Crank length should be related to inseam measurement." Fair enough, I guess.
But then this:
"After much qualitative observation and some informal testing, I have concluded that the standard crank length of 170mm is optimum for a cyclist with a 31-inch inseam."WTF? That's it? Crikey! So, I gather he found some long cranks one day; rode them; liked them; figured out what proportion of his inseam they were, then started a website to encourage lots of people to spend a small fortune on custom cranks, and hurt their knees. Pffft! Ha!

Who's to say that all the guys with 34" inseams using 172.5s weren't using the optimum length? Not him, that's for sure!

And this is him:
https://www.nettally.com/palmk/resume.html
Jee, what a fine athlete and great example for his theory. Would you listen to someone like that who's telling you how to ride a bike faster? Maybe, maybe not.

Then Lennard Zinn -- who is in the business of selling custom cranks, especially long ones -- jumped on the "21.6% of inseam" formula, and that was it!

Both Zinn and Palm are tall guys who were frustrated in the 'old days' about not being able to get cranks longer than 175mm, then, when they finally got some 180s, they liked them and it snowballed.

All ya gotta do is ask yaself why no pro in the whole World is using cranks over 180mm! And this includes some big guys with long legs. There may be some using 180s and slightly longer for time trials, but the longest i know is guys like Boonen, who uses 177.5, but he's 6ft3 or 6'4". These guys are the fastest people on the planet, and they're doing so on regular length cranks. I know Sosenka used 190s or 195s for his hour record, but he's 6ft7!!

Anyway, as I said, I'm just under 6ft with a 35" inseam (89cm, and that's inside leg, not pants inseam), and I got right into long cranks about 6 years ago. I bought some 180s; used them for exclusively for 12 to 18 months; ended up not liking them at all (except for riding off the saddle); went back to 175s for about a month, and now my main length is 172.5. I woulda been just as happy with 170s (maybe even preferred them slightly), but there seems to be many more sets of 7800 DA cranks in 172.5. And i'm even experimenting at the moment with some 165s.

I ended up not liking the 180s, mostly because I got sick of my knees coming up so freaking high. This gave me the very frustrating feeling of not being able to "get on top of" the pedals through most of the downstroke. I was constantly getting off the saddle so I could feel like i was pounding the pedals properly.

I felt no slower at all going back to shorter cranks -- in fact, I initially felt much faster.
There are tests around that have shown no power loss going to cranks as short as 145mm (don't ask me to dig them up ). In my opinion, using different crank lengths pretty much evens out: longer cranks may provide more leverage, but they're harder to push coz the knees come up higher; and vice versa: short cranks may have less leverage, but are easier to push, coz of the reduced knee and hip flexion through the top of the downstroke (higher over the pedals, which is compounded by adjusting saddle height for different lengths).

Long cranks are AWESOME for riding off the saddle, but as soon as you sit down, you're confined to the position problems they present.

I'm a bit disappointed with Zinn mentioning BMX riders using really long cranks, but neglecting to mention that BMXers race almost the WHOLE race off the saddle. This changes everything.

As someone else on here intimated, crank length formulas are more voodoo than anything else. If proportion of leg length is the way to go, then maybe it should be a sliding scale, with relatively longer cranks for shorter people, and vice versa. This is basically what that table on page 1 is.

The bottom line is, aerodynamics trumps all, most of the time, and if long cranks mean your thighs push into your stomach so much that you have to ride too upright, then any possible power advantage would be nullified by lots of extra drag. It goes like this: shorter cranks increases the thigh/waist clearance, so the rider can lower his/her upper body. There's a trend for people to use shorter cranks on time trials, because of this.

Eh, I'm getting tired (it's 1:20am), so if I've left anything out I'll fix it tomorrow.

oldbobcat

Going from 170 to 175 allowed me to drop the saddle 0.5 cm, so . . . I can't explain why, but it was an improvement. Of course, stem length stayed the same. I probably set it back a little bit more, too. It was a long time ago.