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Went back to 180 cranks

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#21 ·
my bike I had 180 on was a climbing demon where I needed ratcheting action to get up rockpiles
 
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#25 ·
Jayem said:
Monkey was busting BB shells from pedal hits...
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OiLoikBoiks said:
Or, monkey see, monkey try, monkey felt more comfortable.

Shortening the cranks on one bike helped solve a muscular issue I was having.
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2 separate reasons, but equally valid. The latter is the convectional reasoning behind crank sizing. Get a length that fits your legs. If that's 180 or 155, great, and great that we have a lot more sizes now.
The former is a more recent "trend" of shorter cranks which some people are jumping on without actually having any real need. They aren't bashing rocks, they don't have short legs. This is very much monkey see monkey do. "hey 150mm cranks are trendy, I need them" as opposed to actually needing them for a functional reason. You end up with uncomfortable cranks for no reasonable trade off.
 
#27 ·
yzedf said:
At 6’4” I won’t ride anything longer than 170 and will probably go with 165 whenever I buy my next crankset.
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Yeah height isn't strictly relevant. I have a 6'7 friend with shorter legs than me. But also everyone has different motion ranges, feet size, knee issues, etc etc. And people also change over time as well. What was comfortable 5 years ago might not be any longer.

Bike geometry also plays a factory. We now sit a lot more forward relative to the cranks, which will change your leg motion.
 
#28 ·
3_Dimensional said:
Lance Canfield the short crank guy says to run cranks that are 20% to 20.5% of your inseam for geared bikes (apart from DH). If you have a 35" inseam, that puts you right at a 180 mm crank length. So for OP, 180 mm cranks may very well still count as "short" even though they are longer than what most people run.
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Yeah, that works if you're on mellow, smooth tracks. Otherwise it's stupid.
 
#30 ·
chomxxo said:
Let me put it simply: If you believe that Tadej Pogačar is best on 165mm cranks with a 33" inseam, that's just fine (20% of leg length). I have a 36.5" inseam. So... 180mm cranks are the perfect fit for me, too.
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And if you don't believe a random percentage based on only one of a dozen critical variables is how you calculate this?
 
#31 ·
It's not random, it's a ratio that helps to illustrate how not everyone needs ultra-short cranks. I'm disturbed that there are very few 180mm crank lengths being sold these days vs a few years ago. Perhaps average-sized cyclists have been riding cranks that are too long, but I haven't been.

smashysmashy said:
And if you don't believe a random percentage based on only one of a dozen critical variables is how you calculate this?
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#32 ·
chomxxo said:
It's not random, it's a ratio that helps to illustrate how not everyone needs ultra-short cranks. I'm disturbed that there are very few 180mm crank lengths being sold these days vs a few years ago. Perhaps average-sized cyclists have been riding cranks that are too long, but I haven't been.
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Well, this is the disconnect between "sizing" needs, and clearance needs, and people just following trends blindly.

20% is random, but you are right that it illustrates length is not meant to be an absolute when it comes to sizing.
 
#33 ·
No it's not random. I suggest that you take 5. You might learn something.

In every aspect of bike fit, there's parts of the bike that sized are proportional to the body. The 20% rule for cranks is not random. It used to be 21-22% and Lennard Zinn is generally credited with that calculation. You can disagree with it but it matches leg length to crank length, which is quite reasonable. Is your saddle height or stem length "random?"

Scientifically, it's been shown that the body can adapt to a wide range of crank lengths before showing a decrease in performance. So there are plenty of people operating within the margin of error, but that doesn't invalidate the rule. Pogi is currently the world's most successful cyclist. The main distinction I'm making is that I'm more like him with 180mm cranks than those who are going to 165mm cranks just because he is.


velo.outsideonline.com

Technical FAQ with Lennard Zinn: When it come to crankarm length - no easy answers

A reader asks for a rule of thumb for crank arm length, and LZ explains that there isn't one.
velo.outsideonline.com velo.outsideonline.com


smashysmashy said:
Well, this is the disconnect between "sizing" needs, and clearance needs, and people just following trends blindly.

20% is random, but you are right that it illustrates length is not meant to be an absolute when it comes to sizing.
Click to expand...
 
#35 ·
Assuming crank length should be proportional at such a fine level of precision to body length (and that there is a correct ratio) seems like a rather large, and unfounded assumption. The vast majority of bike fit rules are based on nothing more than observing what the majority of cyclists are currently doing. Which is why current bike is 2 inches longer (with 8 inch wider bars) than my bike from 20 years ago but both "fit correctly"

The idea of longer cranks for bigger people is reasonable, but pretty much any crank you can by today is within the size range that it's going to be ok for most people and just a matter of personal preference/body shape/flexibility/etc. The reality for mountain bikes is that other constraints are going to have a much larger effect on crank selection than body size, It doesn't matter how tall you are, a 220mm crank just isn't going to work on a MTB.

TLDR: Almost nothing in bike fit is proportional to the human body aside from in the most general sense, and there is a huge range of acceptable fit.
 
#36 ·
Almost everything in bike fit is proportional to the human body.
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DIY Bike Fit: How to Do It

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Older MTBs are poor examples since they were modeled after road bikes starting in the 1990s, and it's been a long hard road breaking those bad habits (now you get the treatment, gravel bikes).

All bikes being sold today are proportional to riders, including reach, saddle height, crank length, bar width, and even wheel size.

The only thing rando is some of the comments...

 
#37 ·
bpw said:
Assuming crank length should be proportional at such a fine level of precision to body length (and that there is a correct ratio) seems like a rather large, and unfounded assumption. The vast majority of bike fit rules are based on nothing more than observing what the majority of cyclists are currently doing. Which is why current bike is 2 inches longer (with 8 inch wider bars) than my bike from 20 years ago but both "fit correctly"

The idea of longer cranks for bigger people is reasonable, but pretty much any crank you can by today is within the size range that it's going to be ok for most people and just a matter of personal preference/body shape/flexibility/etc. The reality for mountain bikes is that other constraints are going to have a much larger effect on crank selection than body size, It doesn't matter how tall you are, a 220mm crank just isn't going to work on a MTB.

TLDR: Almost nothing in bike fit is proportional to the human body aside from in the most general sense, and there is a huge range of acceptable fit.
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I'll go with that.
You can use others experiences as a loose guise, but that's really all it is.

I am quite tall, but ride a small bike. There are very specific fit reasons for this, and that's it. Should anyone else with a 34 inseam ride a small? No idea, but probably not.

For cranks, I like 175. I dislike 165. Never tried 180. On my trails, pedal strikes are rare, so no big deal there.
 
#38 ·
Too much reading of the tea leaves I feel. My 29er has 175mm cranks. I'm not tall, 172-173 cms short, they work just fine for me.
When I built my 27.5 bike, I went to 170 cms. They work just fine. 175 was a touch too long, on smaller wheels & lower profile tyres. After reading all the hype, I tried a set of 165's. I gave them a really good go. Like over a year. Tried to like them, just didn't. Popped the 170's back on, it was like coming home to a nice warm house on a freezing cold night. Built another 27.5 bike, tried the 165's again. Just didn't gel with them. So back to the 170's, happy again. Broke my hip after getting ran over a few years back, it's just happier and more comfortable on 170's than 165's. 165's felt like I was just struggling a bit everywhere.
What you really need to do, is forget the marketing and hype, try them out for yourself, and use whatever your body tells you it's happiest with. That doesn't come out of a formula, or website.
 
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