Bicycle Mechanics - what crank length is right? 170mm, 175mm, or 190mm???

I ride my bike for commuting, a single speed road bike. I am currently using 165mm cranks that came with my bike. I took a look at this site here: http://www.nettally.com/palmk/Crankset.html

So measuring my inseam with that method and plugging it into the forumula i get 190mm, this is with a 34.75 inseam. i am slightly over 6 feet 1 and i find 190mm a bit much, is the site correct? i was considering between 170mm or 175mm but this 190mm is ridiculous, or are they right? what are your thoughts?

Crank length calculators should be taken with a grain of skepticism. They are usually based on the model that people with average-length legs (whatever that is) should be turning average-length cranks (170 mm), and everyone else should use the same proportion.

Truth is, riders with shorter legs ride on cranks that tend to be longer in proportion to their legs than riders with longer legs. And the crazy thing is, as mathematically improbable as it seems, it works for most riders.

190s are an expensive custom shop item, anyway. 170s or 175s would work fine; for single speed I'd favor 170s.

165 is good for spinning a fairly low gear ratio at a higher rpm..
and not putting a pedal hit into a banked corner on the velodrome ,
and becoming an airborne projectile..

long legged, low cadence big ratio may favor the longer crankarm

for added leverage.

if you want 190, then contact Lennard Zinn, CO based custom builder
and a series of bikes, to the Tall Rider..

He got someone to make longer than 180 cranks ..

Bullseye made custom cranks up to 225mm length, and I've heard of tests done with cranks as short as 110mm. As Old Bob said, testing shows that there's very little difference in power production among different length cranks.

Here's a good start on the "real" answers:
http://velonews.competitor.com/2011/06/bikes-and-tech/technical-faq/technical-faq-with-lennard-zinn-when-it-come-to-crankarm-length-no-easy-answers_178528

To take advantage of radically different length cranks, you'd have to have custom frame made to keep the pedals at the right height off the ground. FWIW: I'm 6-foot-4 and I'm quite comfortable spinning 175mm cranks.

The length of the crank is dependent upon the height of the rider but when it comes down to it, it doesn't matter much. The shorter the crank, the faster you have to turn your legs. They assume the taller person has bigger muscles thus the crank is longer as you have the muscle power to turn it. With a shorter or longer crank length, you would adjust the seat height accordingly. A person may have an aggressive frame but don't like the positioning. One could put a higher angled stem on to reduce the aggressiveness, or the more expensive option, shorten the crank length. With the latter, he will lower the saddle/seat post to compensate for the shorter crank length thus reducing the aggressiveness of the frame, the position of the difference between the handlebars to the seat height.

As Jeff noted, crank length has very little to no effect on power and speed when measured objectively but some riders have a strong personal preference and can tell small differences so the subjective part can be important. I'm 5'9" and have 170's on most of my bikes However, I'm pretty unfussy about crank length and have switched from bikes with 170's to another with 175's and never noticed any change. Others think a 2.5 mm length difference is a big deal.

The calculator that recommended 190 mm cranks for someone 6'1" seems WAY out of line with conventional recommendations and probably should be ignored. I expect you will be happy with 175's.

This table I found here (http://linuxandfriends.com/2008/11/23/how-to-find-the-correct-crank-length-for-your-bicycle/) seems to make more sense.

60 to 65cm 150mm
66 to 70cm 155mm
72 to 75cm 160mm
75 to 78cm 162.5mm
79 to 81cm 165mm
82 to 83cm 167.5mm
83 to 86cm 170mm to 172.5mm
87 to 90cm 175mm to 177.5mm
91 to 94cm 180mm
94cm plus 185mm

It says you should prolly be on 175s, but who knows?

IMO you really need to try different lengths and give yourself a chance to get used to it before making a call on your preferred length; I'm 175cm with an 82cm inseam and only ever ridden 170s, but after getting hold of some 175s, there's no turning back - I have more power with em; it feels like my chainring is 1t smaller. They took a bit of getting used to (I chose not to lower my seat as well, which seemed to work), but I found I could still spin them pretty quick. Maybe I could even go to 177.5s before it puts a meaningful dent in my redline (which, come to think of it, I have pretty much no reason to hit anyway).

Thanks for the table. I'm used to 170mm but keep on wondering whether I'd feel more "liberated" with 175mm. But, my inseam is only 83.5cm.

hule, My road bike's crankarms ranged from 165 mm to 175 mm (I'm 6', ~33.5" inseam). My max cadence is down slightly with the 175 mm crankarms when compared to 170 mm crankarms, but with either when I approach max cadence, I upshift.

Barring a physical issue I think cyclists are quite adaptable to crankarm length.

Brad

+1 for 175mm cranks I am 6'2 with 33 pants inseam and they feel fine.

well at least it's not a Fixie, so you can corner with the inside pedal up.

Thanks for the table. I'm used to 170mm but keep on wondering whether I'd feel more "liberated" with 175mm. But, my inseam is only 83.5cm.And mine is only 82cm, but as I said, there's no turning back.

If you have a good spin, it's win - the extra 5mm is no big deal next to the extra leverage.

170mm is generally treated as a default size too often, IMO. Thus way too many 170mm cranks exist, making it hard to experience anything else. Definitely worth trying a different size, but I had to find a set of cranks on a junk bike before it was practical for me.

I'm 6'8" with a 101cm inseam and I have 210mm cranks on one of my bikes. Due to a biomechanical issue (janky hip joint) they're a touch long.
After a few hours on my bicycle with 175mm cranks I'm noticeably more worn out (leg muscle wise) than on my bicycle with 210mm cranks.

The 175mm cranks feel like a child's bike, they feel very small. Though there's no night and day change in power output, my body is MUCH happier with longer cranks.

The only downsides are pedal strike, heel strike on panniers, and toe over-lap with shorter top tubes.

Though this forum shoots down the prospect of longer cranks, from my personal experience they're very much a boon for us giants.

I purchased mine from HS Cycles (http://www.hscycle.com/Pages/customcrankset.html) which also make Zinn's cranks, but cost significantly less.

Wow, can you show us a pic of your bike?

After reading Sheldon's article on crank length, I got the idea in my head that longer can be bad but there's no downside to shorter arms. http://sheldonbrown.com/cranks.html

On that note, all my road bikes have 170s (I'm 5' 9") and all my mountain bikes have 170s or 175s. Honestly, I don't think it's a huge deal because I've never been able to tell the difference from one bike to the next. I would like to try some 165s though for my next fixed gear build...

On that note, all my road bikes have 170s (I'm 5' 9") and all my mountain bikes have 170s or 175s. Honestly, I don't think it's a huge deal because I've never been able to tell the difference from one bike to the next. I would like to try some 165s though for my next fixed gear build...
I'm your height and that's my experience exactly. Going from my road bikes, all with 170 mm cranks, to my MTB with 175 mm cranks was seamless. However, I've talked to other riders who make a big deal about crank length and claim they can feel minor differances.

The 165 mm cranks on a fixed gear make sense since you have to pedal through corners and the additional ground clearance can be beneficial.

The only corners fixed-gear bikes should be turning on are banked anyway : p

The only corners fixed-gear bikes should be turning on are banked anyway : p
Haven't seen the hipsters and messengers much huh?

*should*

; )

Suspect the preponderance of people poo-pooing long cranks is because 95% of people are not very tall. Therefore they've always easily found available crank sizes that are about right. They can't imagine a crank length that just feels way too short.

To reverse the situation, what if the only generally available crank sizes were say 180mm to 195mm. And yet all you fair-average sized persons were forced to ride them. See how you'd like it on fast road rides. "But crank length doesn't make much difference." :-)

I'm 6'1" with 35" inseam. When I changed from 175mm to 180mm cranks in 2002 I never looked back. The immediate subjective feeling of riding 180mm was so "right" . . . . but more to the point I was able to sprint faster, sustain standing climbs 2-3 times longer, and keep my cadence in 90-110 (whereas on 175mm I was spinning 110-140mm in competitive rides) with ultimately less fatigue.

Now when I get on a bike with less than 175mm it feels like a silly circus bike. Really.

So to the OP I say: get a set of 180s. Truvative and SRAM have some double road sets that can be had for a reasonable door fee.

Though this forum shoots down the prospect of longer cranks, from my personal experience they're very much a boon for us giants.
.
Didn't mean to shoot down the idea of long cranks for giants, just the model that would put the original poster on 190s. Interpolating from your model, the original poster should be on 173.9 cm cranks. That's right in the ballpark of every one of our suggestions.

Interpolating from your model, the original poster should be on 173.9 cm cranks. That's right in the ballpark of every one of our suggestions.

LOL, 1,739mm is so not in the ballpark : p

Bullseye made custom cranks up to 225mm length, and I've heard of tests done with cranks as short as 110mm. As Old Bob said, testing shows that there's very little difference in power production among different length cranks.

Here's a good start on the "real" answers:
http://velonews.competitor.com/2011/06/bikes-and-tech/technical-faq/technical-faq-with-lennard-zinn-when-it-come-to-crankarm-length-no-easy-answers_178528

To take advantage of radically different length cranks, you'd have to have custom frame made to keep the pedals at the right height off the ground. FWIW: I'm 6-foot-4 and I'm quite comfortable spinning 175mm cranks.

Five foot nine and have a 33 inch riding inseam... I too prefer 175's which might be a function of my femur length in relation to total leg length.

we build custom bikes for extremely tall riders and for some of them who might have a 40 inch inseam, a 190mm crank makes sense when that is built into a custom frame that also accounts for unusual dimensions.

This is the current breakdown for manufacturers. There isn't a 190 out there.

175 for mountain bikes
172.5 for road bikes
167.5 or 170mm for track bikes.

Take your pick

Hey Mondrian, that's no breakdown for manufacturers, that's someone's idea of what size cranks belong on what type of bike for one rider. It doesn't exactly explain the existence of 175mm road cranks, for example...

Also, http://zinncycles.com/Zinn/index.php/components/custom-cranks http://www.hscycle.com/Pages/customcrankset.html

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?

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

LOL, 1,739mm is so not in the ballpark : p

Oops, 17.39 cm.

Five foot nine and have a 33 inch riding inseam... I too prefer 175's which might be a function of my femur length in relation to total leg length.

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.

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.

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

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.

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.

I ride my bike for commuting, a single speed road bike. I am currently using 165mm cranks that came with my bike. I took a look at this site here: http://www.nettally.com/palmk/Crankset.html
?

I'm not shooting the messenger, but Gord, I wish this website would just go away and die. :thumb: 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?! :D 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:
http://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:
http://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 :p). 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.

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.

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.