Cranks... do women need shorter ones? Huh?

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Cranks... do women need shorter ones? Huh?

Postby Missy24 » Sun May 30, 2010 1:37 pm

Hey guys

Can you tell me about crank arms?

TREK WSD products claim 4 reasons as to why women need a different bike, this does not include geometry yet, is the length of the cranks on your bike specific to a rider being male and female?

In regards to WSD bikes Trek says, "Shorter crank arms improve leverage for a more efficient pedal stroke."

How accurate is this? Or is this just a ploy to get women to buy a lower spec bike at a higher price?

Thanks guys.
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by BNA » Sun May 30, 2010 2:08 pm

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Re: Cranks... do women need shorter ones? Huh?

Postby Timguy » Sun May 30, 2010 2:08 pm

I had a bmx with shorter cranks -2 or 3 cm shorter than normal - (just so they wouldn't be in the way while doing tricks). Actually riding the bike was a pain in the butt. They don't have better leverage, and the statement that they are more efficient is a bit misleading. Sure they have less distance to travel to make a full rotation, but you pedal that rotation with less power because you have less leverage. And I honestly can not think of any reason why shorter cranks would be better for women. To me that just sounds like a stupid claim by the manufacturer.

But this is all just from my experience.
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Re: Cranks... do women need shorter ones? Huh?

Postby hartleymartin » Sun May 30, 2010 2:13 pm

Crank arm length is down to personal preference. One calculation reckons that I need 190mm cranks, but I am not fussed. I own several bicycles, which have 165, 170, 172.5 and 175mm cranks, and for the most part I don't really feel any difference. I actually prefer the 165 (but that might be really because it's on my favourite bicycle). Try entering your inseam length into this online cyclist's crank length calculator and see what you get. A bit like bicycle spoke length calculators, they all disagree to an extent. I get measurements anywhere from 175 to 195mm being spat out by the various calculators. At least the spoke-length calculators agree to within 1mm usually.
Last edited by hartleymartin on Sun May 30, 2010 2:22 pm, edited 1 time in total.
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Re: Cranks... do women need shorter ones? Huh?

Postby Nobody » Sun May 30, 2010 2:14 pm

http://www.cyclefitcentre.com/pdf%20fin ... _final.pdf

A few things I found when shortening crank length.

Cadence goes up.
Gearing gets taller by the % change of the crank length.

In the end, it is about correct fit. It only really matters if you are too short for your cranks.
Last edited by Nobody on Sun May 30, 2010 2:22 pm, edited 1 time in total.
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Re: Cranks... do women need shorter ones? Huh?

Postby Missy24 » Sun May 30, 2010 2:21 pm

Hey guys

sorry but he quesion was just generic, its not for me personally... here they are again, this is a science type question

In regards to WSD bikes Trek says, "Shorter crank arms improve leverage for a more efficient pedal stroke."

How accurate is this? Or is this just a ploy to get women to buy a lower spec bike at a higher price?


This isn't about me, I know how to buy a bike... and I know what I want in a bike

I'm trying to figure out whats behind a WSD, its starting to sound like a whole lot of showtime

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Re: Cranks... do women need shorter ones? Huh?

Postby Nobody » Sun May 30, 2010 2:25 pm

Missy24 wrote:
In regards to WSD bikes Trek says, "Shorter crank arms improve leverage for a more efficient pedal stroke."

How accurate is this? Or is this just a ploy to get women to buy a lower spec bike at a higher price?
Read the below link and judge for yourself.

http://www.ncbi.nlm.nih.gov/pubmed/11417428
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Re: Cranks... do women need shorter ones? Huh?

Postby hannos » Sun May 30, 2010 2:26 pm

Missy24 wrote:[b]
In regards to WSD bikes Trek says, "Shorter crank arms improve leverage for a more efficient pedal stroke."


Well if I remember my physics lessons correctly, shorter cranks = less leverage.
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Re: Cranks... do women need shorter ones? Huh?

Postby Missy24 » Sun May 30, 2010 2:31 pm

Nobody wrote:
Missy24 wrote:
In regards to WSD bikes Trek says, "Shorter crank arms improve leverage for a more efficient pedal stroke."

How accurate is this? Or is this just a ploy to get women to buy a lower spec bike at a higher price?
Read the below link and judge for yourself.

http://www.ncbi.nlm.nih.gov/pubmed/11417428

thanks.. appreciate it
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Re: Cranks... do women need shorter ones? Huh?

Postby GraemeK » Sun May 30, 2010 2:43 pm

Suggesting that women all need shorter cranks is a silly as suggesting all women need pink bikes ( perhaps they do?) But seriously it is just another way to tune a bike to your physical dimensions and your preferred style of riding, probably has more to do with the anatomy of the fibers of your muscles than your sex. My neighbors daughter who is 6'-2'' tall and has crazy long legs reckons 155 cranks seem like her feet are kind of trapped in a hamster wheel -- Odd description I know but clearly it is not a situation that suits her, the longest cranks I had floating around to give her are 170 which she much prefers but I reckon even longer would work well for her. At the same time I have a woman I built a road bike for who is much shorter and asked for short cranks to begin with but after a few months at my suggestion, went back to the 170's she had on her previous bike - she then realized the shorter cranks just never felt right - told me she had been disappointed in the new bike but had not wanted to tell me but that the longer cranks had transformed it and she was now thrilled with it. So I reckon that crank length is not really a gender related issue as much as a sales pitch.
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Re: Cranks... do women need shorter ones? Huh?

Postby hartleymartin » Sun May 30, 2010 3:16 pm

GraemeK wrote:Suggesting that women all need shorter cranks is a silly as suggesting all women need pink bikes ( perhaps they do?) But seriously it is just another way to tune a bike to your physical dimensions and your preferred style of riding, probably has more to do with the anatomy of the fibers of your muscles than your sex. My neighbors daughter who is 6'-2'' tall and has crazy long legs reckons 155 cranks seem like her feet are kind of trapped in a hamster wheel -- Odd description I know but clearly it is not a situation that suits her, the longest cranks I had floating around to give her are 170 which she much prefers but I reckon even longer would work well for her. At the same time I have a woman I built a road bike for who is much shorter and asked for short cranks to begin with but after a few months at my suggestion, went back to the 170's she had on her previous bike - she then realized the shorter cranks just never felt right - told me she had been disappointed in the new bike but had not wanted to tell me but that the longer cranks had transformed it and she was now thrilled with it. So I reckon that crank length is not really a gender related issue as much as a sales pitch.
Graeme


Women typically have longer legs in relationship to their overall height. I'm roughly the same height as this girl, and I'd imagine that all else being equal she would most probably prefer longer cranks than me because her legs would be longer than mine.
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Re: Cranks... do women need shorter ones? Huh?

Postby rustguard » Sun May 30, 2010 3:52 pm

Missy24 wrote:"Shorter crank arms improve leverage for a more efficient pedal stroke."

lol yeah a shorter ruler will let you measure further too
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Re: Cranks... do women need shorter ones? Huh?

Postby Kalgrm » Sun May 30, 2010 5:01 pm

Missy24 wrote:In regards to WSD bikes Trek says, "Shorter crank arms improve leverage for a more efficient pedal stroke.[/b]

I agree with the statement, but I don't think it's only one gender which would benefit from shorter cranks. I've argued in many places on this forum about shorter cranks being more efficient, so I'm not going to beat the dead horse again.

I run 145mm cranks and noticed an improvement as soon as I switched to them.

Cheers,
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Re: Cranks... do women need shorter ones? Huh?

Postby GraemeK » Sun May 30, 2010 5:15 pm

I agree with Kalgrm - Heaps of people regardless of gender would benefit from shorter cranks and I hope my example above did not suggest otherwise. In the end its anatomy and riding style that makes one length more satisfactory than another not gender and given that 170 cranks seem to be the default and 145 relatively uncommon it is quite possible that some significant percentage of riders would do better with shorter cranks if they had the opportunity to try them.
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Re: Cranks... do women need shorter ones? Huh?

Postby Missy24 » Sun May 30, 2010 5:27 pm

Kalgrm wrote:
Missy24 wrote:In regards to WSD bikes Trek says, "Shorter crank arms improve leverage for a more efficient pedal stroke.[/b]

I agree with the statement, but I don't think it's only one gender which would benefit from shorter cranks. I've argued in many places on this forum about shorter cranks being more efficient, so I'm not going to beat the dead horse again.

I run 145mm cranks and noticed an improvement as soon as I switched to them.

Cheers,
Graeme

Ok, but why does it improve the performance? And why state it specifically for women as though this is what makes a WSD bike WSD?

Trek outlines 4 points that makes a WSD bike WSD

1. Handle bar width
2. seat
3. leavers
4. cranks

I don't want an argument, but I am looking for an answer as to why this is specific to a WSD bike...

Graeme I'm not saying your wrong at all, but my basic understanding of physics (ok so I asked someone smarter than me and they said...) tells us that the statement is incorrect
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Re: Cranks... do women need shorter ones? Huh?

Postby Missy24 » Sun May 30, 2010 5:30 pm

GraemeK wrote:Suggesting that women all need shorter cranks is a silly as suggesting all women need pink bikes ( perhaps they do?) But seriously it is just another way to tune a bike to your physical dimensions and your preferred style of riding, probably has more to do with the anatomy of the fibers of your muscles than your sex. My neighbors daughter who is 6'-2'' tall and has crazy long legs reckons 155 cranks seem like her feet are kind of trapped in a hamster wheel -- Odd description I know but clearly it is not a situation that suits her, the longest cranks I had floating around to give her are 170 which she much prefers but I reckon even longer would work well for her. At the same time I have a woman I built a road bike for who is much shorter and asked for short cranks to begin with but after a few months at my suggestion, went back to the 170's she had on her previous bike - she then realized the shorter cranks just never felt right - told me she had been disappointed in the new bike but had not wanted to tell me but that the longer cranks had transformed it and she was now thrilled with it. So I reckon that crank length is not really a gender related issue as much as a sales pitch.
Graeme

Thanks Graeme.

Did your daughter end up adjusting her seat height? I can understand how she would feel like a hamster
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Re: Cranks... do women need shorter ones? Huh?

Postby Missy24 » Sun May 30, 2010 5:33 pm

I'm kind of thinking that if your really short then it may make a difference.... thoughts?

Or if your really tall?


:? why did I start a topic that required information?
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Re: Cranks... do women need shorter ones? Huh?

Postby Nobody » Sun May 30, 2010 5:46 pm

Missy24 wrote:Trek outlines 4 points that makes a WSD bike WSD

1. Handle bar width
2. seat
3. leavers
4. cranks
5. May have shorter top tubes for frame size
6. Gotta have pink in the colour range. :wink:

Missy24 wrote:Graeme I'm not saying your wrong at all, but my basic understanding of physics (ok so I asked someone smarter than me and they said...) tells us that the statement is incorrect
The explanation of shorter cranks having better leverage for shorter legged people (and women are generally shorter) is about how far the knee has to bend rather than the leverage of the crank itself.

If you reduce the crank length by 6% (175 to 165) it effectively increases the gearing by 6% which can obviously be matched by reducing the overall gearing by 6% to match the increase in gearing due to the lack of crank leverage.

So now you have the same mechanical leverage but better biological leverage as the short person's knee is bending less, so his/her leg is stronger with a less bent leg.

Edit: Grammar
Last edited by Nobody on Sun May 30, 2010 6:07 pm, edited 1 time in total.
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Re: Cranks... do women need shorter ones? Huh?

Postby Missy24 » Sun May 30, 2010 5:55 pm

So basically it comes down to height and its got nothing to do about being a man or a women.... pfff

Right so basically I've decided that all points that trek has come up with is actually bogus in relation to what they say makes a WSD bike, except for the WSD saddle.
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Re: Cranks... do women need shorter ones? Huh?

Postby Kalgrm » Sun May 30, 2010 5:57 pm

Yep, most people are forgetting their biomechanics when they quote the physics of longer levers. It's not just the length of the lever, but how the body interacts with that lever. (Actually, most people are forgetting their physics too. Longer levers are about increasing torque. Most of us don't want to apply high amounts of torque through the knees and run higher cadences to avoid it.)

As far as being "specific to women" as claimed by Trek: I'd say they are assuming women are generally shorter than men, so a shorter crank suits the length of their legs.

Cheers,
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Re: Cranks... do women need shorter ones? Huh?

Postby Kalgrm » Sun May 30, 2010 5:58 pm

Missy24 wrote:Right so basically I've decided that all points that trek has come up with is actually bogus in relation to what they say ...

Welcome to the world of marketing.

;)
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Re: Cranks... do women need shorter ones? Huh?

Postby GraemeK » Sun May 30, 2010 5:58 pm

Hi Missy
The leggy girl is a neighbor not my progeny although I would willingly claim her.
The bike she rides is a good fit for her - 61cm frame and is well set up. I adjusted the seat height each time I changed the cranks which I have now done a few times. I have to say the most difficult thing I have found is trying to find a seat and seat position that is comfortable for her. We seem to have a workable arrangement but I reckon girls and bike seats are just a problem -- my wife has struggled with the seat thing as well.
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Re: Cranks... do women need shorter ones? Huh?

Postby Missy24 » Sun May 30, 2010 6:05 pm

Kalgrm wrote:
Missy24 wrote:Right so basically I've decided that all points that trek has come up with is actually bogus in relation to what they say ...

Welcome to the world of marketing.

;)

I love marketing especially commercials (the good ones, not this Australian crap, but the million dollar yankee stuff and pearl izumi adds) but I don't like being misled...

In the next session we'll be looking at the geometry of wsd compared to regular
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Re: Cranks... do women need shorter ones? Huh?

Postby Missy24 » Sun May 30, 2010 6:06 pm

GraemeK wrote:Hi Missy
The leggy girl is a neighbor not my progeny although I would willingly claim her.
The bike she rides is a good fit for her - 61cm frame and is well set up. I adjusted the seat height each time I changed the cranks which I have now done a few times. I have to say the most difficult thing I have found is trying to find a seat and seat position that is comfortable for her. We seem to have a workable arrangement but I reckon girls and bike seats are just a problem -- my wife has struggled with the seat thing as well.
Gareme

It can be an expensive process
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Re: Cranks... do women need shorter ones? Huh?

Postby MiG » Mon May 31, 2010 12:59 am

Kalgrm wrote:(Actually, most people are forgetting their physics too. Longer levers are about increasing torque. Most of us don't want to apply high amounts of torque through the knees and run higher cadences to avoid it.)

If we're going to bring physics into it, let's do it properly. Torque about the bottom bracket is unrelated to torque about the knee. Different points, different torques, changing one does not necessarily affect the other.
This is by no means justifying long cranks (I happen to prefer the smaller range of motion of my 170 mm cranks despite being 183 cm tall with longish legs), but physics must not be misrepresented.
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Re: Cranks... do women need shorter ones? Huh?

Postby rustguard » Mon May 31, 2010 2:01 am

MiG wrote:but physics must not be misrepresented.

totally agree, the word leverage was a very poor choice by their marketing team.
Lazy marketing personnel who were in a hurry to get to the pub.
took me 30 seconds to come up with this.

"Shorter crank arms improve power transfer for a more efficient pedal stroke."

Kalgrm wrote:I run 145mm cranks and noticed an improvement as soon as I switched to them.

those are freakishly short cranks, do you run those on your road bike or your recumbent?
I have heard you praise these before, I must say I am curious about just how they perform. I have never known anyone who rides with cranks that short so its very difficult to get an opinion. What cadence are you running on average.

about 7 or 8 years ago. I rode with 165mm for about 6 months because i wanted to get my cadence up higher. I was so glad to get back to longer cranks it was almost driving me barmy.
I love the power I get from my 175mm, very noticeable on hills. but yes I have to consciously push my cadence.
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