Crank lengths - why so little variation?

[still me]

Why don't we see more variation in crank lengths?

Frames commonly vary form 53 to 62cm, but cranks only vary from 165 to
172.5, maybe 175 (commonly anyway).

Are people's bodies proportioned such that the crank lengths don't
need to vary - or is this just a cheaper way out for manufacturers? (I
se the problem of BB height restricting the upper end).

I know little about anatomical proportions, but it seems like the guy
on the 53cm frame will have much shorter legs (typically) and need a
much shorter crank than the guy on a 63cm frame.

 

[DougC]

still me wrote:
> Why don't we see more variation in crank lengths?
>
> Frames commonly vary form 53 to 62cm, but cranks only vary from 165 to
> 172.5, maybe 175 (commonly anyway).
>
> Are people's bodies proportioned such that the crank lengths don't
> need to vary - or is this just a cheaper way out for manufacturers? (I
> se the problem of BB height restricting the upper end).
>
> I know little about anatomical proportions, but it seems like the guy
> on the 53cm frame will have much shorter legs (typically) and need a
> much shorter crank than the guy on a 63cm frame.
>
>
You're not silly with this, it /does/ make sense that everyone shouldn't
be using the same length cranks. They're out there, but generally not
real easy to find.

There are crank shorteners such as those from Tandems East that fit on
most regular cranks; these push out the Q-factor but have the advantage
that they have four different hole positions, so you can experiment to
try to see what length works best for you.
http://www.hostelshoppe.com/cgi-bin/readitem.pl?Accessory=1033761548
however--the Tandems East shorteners are mostly noted as being for
children--meaning you might be looking at a loss of strength when you
use them.

The only cranks manufactured short I've seen lately are the DaVinci
road/doubles, available in 150mm and 160mm lengths.
http://www.hostelshoppe.com/cgi-bin/readitem.pl?Accessory=1152835590

Also there are a couple people that will shorten certain models of
cranks for you--cut them off and drill+tap another pedal hole in each.
At least one guy will shorten cranks you send him, or you can order new
ones from him already shortened. Although--I've only seen these
shortening-services advertised on recumbent boards. Obviously on most
recumbents you cannot stand on the pedals at all--so there is much less
risk of critical injury from breakage.

One might assume that having less leverage would be detrimental to your
performance, but oddly enough, most [recumbent] riders /don't/ report
losing power output when they switched to shorter cranks.
~

 

[[email protected]]

On Sat, 28 Apr 2007 18:06:27 GMT, still me <[email protected]>
wrote:

>Why don't we see more variation in crank lengths?
>
>Frames commonly vary form 53 to 62cm, but cranks only vary from 165 to
>172.5, maybe 175 (commonly anyway).
>
>Are people's bodies proportioned such that the crank lengths don't
>need to vary - or is this just a cheaper way out for manufacturers? (I
>se the problem of BB height restricting the upper end).
>
>I know little about anatomical proportions, but it seems like the guy
>on the 53cm frame will have much shorter legs (typically) and need a
>much shorter crank than the guy on a 63cm frame.

Dear Me,

First, you're not crazy.

Few standard cranks are available in 160 to 180 mm lengths, but riders
are widely available in 64 to 76 inch lengths (5'4" to 6'4"), with
legs that vary in the same proportion.

From 160 mm to 180 mm, the cranks increase only 12.50%, while the
people increase 18.75%, about a 50% greater change in length.

There are several reasons why crank lengths don't vary as much as
actual leg lengths.

The vast majority of customers fit ordinary bicycles just fine.

Really tall people are used to suffering.

Really long cranks tend to hit the ground.

Most of all, it turns out that crank length doesn't really matter
much. During ordinary riding, your feet move in a slow, unnatural,
circular fashion at low pressure, at least compared to jogging.

A brisk walk is about 4 mph. Here's a table of foot speed around the
pedal circle in mph:

160mm 170mm 180mm
60 rpm 2.25 2.39 2.53
90 rpm 3.37 3.58 3.79

Studies show that power output and efficiency don't change much from
long to short cranks. Here's post with some details:

http://groups.google.com/group/rec.bicycles.tech/msg/7dc8a0fa1309e1b7

Changing cranks from 120 mm to 220 mm (!) altered power only 5%.

Cheers,

Carl Fogel

 

[Bill Sornson]

still me wrote:

> Why don't we see more variation in crank lengths?

Squidly?

 

[[email protected]]

On Apr 28, 8:56 pm, [email protected] wrote:
> On Sat, 28 Apr 2007 18:06:27 GMT, still me <[email protected]>
> wrote:
>
> >Why don't we see more variation in crank lengths?
>
> >Frames commonly vary form 53 to 62cm, but cranks only vary from 165 to
> >172.5, maybe 175 (commonly anyway).
>
> >Are people's bodies proportioned such that the crank lengths don't
> >need to vary - or is this just a cheaper way out for manufacturers? (I
> >se the problem of BB height restricting the upper end).
>
> >I know little about anatomical proportions, but it seems like the guy
> >on the 53cm frame will have much shorter legs (typically) and need a
> >much shorter crank than the guy on a 63cm frame.
>
> Dear Me,
>
> First, you're not crazy.
>
> Few standard cranks are available in 160 to 180 mm lengths, but riders
> are widely available in 64 to 76 inch lengths (5'4" to 6'4"), with
> legs that vary in the same proportion.
>
> From 160 mm to 180 mm, the cranks increase only 12.50%, while the
> people increase 18.75%, about a 50% greater change in length.
>
> There are several reasons why crank lengths don't vary as much as
> actual leg lengths.
>
> The vast majority of customers fit ordinary bicycles just fine.
>
> Really tall people are used to suffering.
>
> Really long cranks tend to hit the ground.
>
> Most of all, it turns out that crank length doesn't really matter
> much. During ordinary riding, your feet move in a slow, unnatural,
> circular fashion at low pressure, at least compared to jogging.
>
> A brisk walk is about 4 mph. Here's a table of foot speed around the
> pedal circle in mph:
>
> 160mm 170mm 180mm
> 60 rpm 2.25 2.39 2.53
> 90 rpm 3.37 3.58 3.79
>
> Studies show that power output and efficiency don't change much from
> long to short cranks. Here's post with some details:
>
> http://groups.google.com/group/rec.bicycles.tech/msg/7dc8a0fa1309e1b7
>
> Changing cranks from 120 mm to 220 mm (!) altered power only 5%.
>
> Cheers,
>
> Carl Fogel

I have bikes with cranks ranging from 165mm to 195mm. I go back and
forth on what I think about it. I think however that these tests that
show ranges of "only" 5% do not take into account long term
adaptations to the cranks.

Right now my thinking is that unless you are within a hair's breadth
of your maximum potential, there are so many other factors involved in
the comfort and performance of a bicycle that even large differences
in crank length make for pratical purposes no difference. I look at it
in the same way I look at stem length. There is no "wrong" stem
length, but in general larger people prefer longer ones, while
shorter people prefer shorter ones, with a good deal of variation. It
is essentially a comfort issue.

If someone thinks they would be better suited to either shorter than
normal or longer than normal cranks, they probably will be!

Joseph

 

[Nick Payne]

TA make their cranks in lengths from 150mm to 185mm, Thorn Cycles in the UK
offer their cranks in lengths from 140mm to 175mm.

"still me" <[email protected]> wrote in message
news:[email protected]...
> Why don't we see more variation in crank lengths?
>
> Frames commonly vary form 53 to 62cm, but cranks only vary from 165 to
> 172.5, maybe 175 (commonly anyway).
>
> Are people's bodies proportioned such that the crank lengths don't
> need to vary - or is this just a cheaper way out for manufacturers? (I
> se the problem of BB height restricting the upper end).
>
> I know little about anatomical proportions, but it seems like the guy
> on the 53cm frame will have much shorter legs (typically) and need a
> much shorter crank than the guy on a 63cm frame.
>
>

 

[Werehatrack]

On Sat, 28 Apr 2007 18:06:27 GMT, still me <[email protected]> may
have said:

>Why don't we see more variation in crank lengths?

Lack of demand, mostly.

>Frames commonly vary form 53 to 62cm, but cranks only vary from 165 to
>172.5, maybe 175 (commonly anyway).

IME, 175 is more common than 165, and 170 comes in a strong second.
What's often lamented is the difficulty of finding a 180 or longer
crank, as many tall riders would prefer one. (Yes, *some* cranks can
be had in 180 and longer, but the prices are usually quite steep
unless you can use a BMX crank...in which case you're going to find
the longer sizes readily available.)

>Are people's bodies proportioned such that the crank lengths don't
>need to vary - or is this just a cheaper way out for manufacturers?

I do not know if any valid research has been conducted to determine if
taller or longer-legged riders would benefit from a longer crank.
There has been discussion of the disproportionality, but I haven't
followed the technical end closely. If I could afford a 185 or 190
crank for one of my rides, I'd have at least a personal opinion to
offer, but I haven't found one that's within my budget as yet.
Although it can be postulated that manufacturers benefit from limited
optional characteristics in a profit, they also benefit from increased
sales of a product that is able to be fine-tuned by replacement of a
component to achieve a better match to the user's requirements. I
doubt that the component makers are the problem in this instance.

>(I
>se the problem of BB height restricting the upper end).

Not as big of a problem as it might seem, really.

>I know little about anatomical proportions, but it seems like the guy
>on the 53cm frame will have much shorter legs (typically) and need a
>much shorter crank than the guy on a 63cm frame.

Logic would seem to dictate that this should be true, but logic is a
little tweeting bird, chirping in a meadow. Logic is wreath of pretty
flowers that smell bad. OTOH, can either the faceless monolitic
corporate entities or the often-misinformed user base be trusted to
provide impartial and accurate ansers to this question either? I
think not.







--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

 

[Qui si parla Campagnolo]

On Apr 28, 12:56 pm, [email protected] wrote:
> On Sat, 28 Apr 2007 18:06:27 GMT, still me <[email protected]>
> wrote:
>
> >Why don't we see more variation in crank lengths?
>
> >Frames commonly vary form 53 to 62cm, but cranks only vary from 165 to
> >172.5, maybe 175 (commonly anyway).
>
> >Are people's bodies proportioned such that the crank lengths don't
> >need to vary - or is this just a cheaper way out for manufacturers? (I
> >se the problem of BB height restricting the upper end).
>
> >I know little about anatomical proportions, but it seems like the guy
> >on the 53cm frame will have much shorter legs (typically) and need a
> >much shorter crank than the guy on a 63cm frame.
>
> Dear Me,
>
> First, you're not crazy.
>
> Few standard cranks are available in 160 to 180 mm lengths, but riders
> are widely available in 64 to 76 inch lengths (5'4" to 6'4"), with
> legs that vary in the same proportion.
>
> From 160 mm to 180 mm, the cranks increase only 12.50%, while the
> people increase 18.75%, about a 50% greater change in length.
>
> There are several reasons why crank lengths don't vary as much as
> actual leg lengths.
>
> The vast majority of customers fit ordinary bicycles just fine.
>
> Really tall people are used to suffering.
>
> Really long cranks tend to hit the ground.
>
> Most of all, it turns out that crank length doesn't really matter
> much. During ordinary riding, your feet move in a slow, unnatural,
> circular fashion at low pressure, at least compared to jogging.

Bing, bing, bing, we have a winner!!!!
>
> A brisk walk is about 4 mph. Here's a table of foot speed around the
> pedal circle in mph:
>
> 160mm 170mm 180mm
> 60 rpm 2.25 2.39 2.53
> 90 rpm 3.37 3.58 3.79
>
> Studies show that power output and efficiency don't change much from
> long to short cranks. Here's post with some details:
>
> http://groups.google.com/group/rec.bicycles.tech/msg/7dc8a0fa1309e1b7
>
> Changing cranks from 120 mm to 220 mm (!) altered power only 5%.
>
> Cheers,
>
> Carl Fogel

 

[Greg Berchin]

On Sun, 29 Apr 2007 02:06:53 -0600, Werehatrack
<[email protected]> wrote:

>I do not know if any valid research has been conducted to determine if
>taller or longer-legged riders would benefit from a longer crank.

I'm 6'4" tall with a 36" inseam. I've always been a good sprinter but a
really pathetic climber. I thought that longer crank arms would help
with the climbing, so I put 175mm on my road bike and 180mm on my
mountain bike. Well, they didn't help the climbing but they did hurt
the sprinting (at least it feels that way). I'll probably go back to
170mm on my next bike buildup.

 

[DougC]

Qui si parla Campagnolo wrote:
>>
>> The vast majority of customers fit ordinary bicycles just fine.
>>

This is a difficult claim to make, without having tried anything
different.....

> Bing, bing, bing, we have a winner!!!!

The point of going to different-length cranks is not that you'd produce
any power gain out of it, but that you may be suffering knee problems as
a result of using too deep of a knee bend.

And the assertion that "taller riders are used to suffering" is rather
off-target; if anything, a taller rider with normal length cranks would
be using cranks that are essentially shorter than they should
be--sparing them the knee-extension problems.

Do taller riders have lower incidences of knee problems from riding?
Perhaps the question here is not if taller riders should be using
/longer/ cranks, but if everyone else should be using /shorter/ cranks....
~

 

[John Forrest Tomlinson]

On Sat, 28 Apr 2007 18:06:27 GMT, still me <[email protected]>
wrote:

>Why don't we see more variation in crank lengths?

I never understood this either.
--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************

 

[[email protected]]

On Apr 29, 5:18 pm, DougC <[email protected]> wrote:
> Qui si parla Campagnolo wrote:
>
>
>
> >> The vast majority of customers fit ordinary bicycles just fine.
>
> This is a difficult claim to make, without having tried anything
> different.....
>
> > Bing, bing, bing, we have a winner!!!!
>
> The point of going to different-length cranks is not that you'd produce
> any power gain out of it, but that you may be suffering knee problems as
> a result of using too deep of a knee bend.
>
> And the assertion that "taller riders are used to suffering" is rather
> off-target; if anything, a taller rider with normal length cranks would
> be using cranks that are essentially shorter than they should
> be--sparing them the knee-extension problems.

By suffering I'm pretty sure he meant that tall/large people are used
to all manner of tools (scissor handles, counter top heights, airline
seats, car doors, etc) not fitting them, so why should crank arms be
any different?

> Do taller riders have lower incidences of knee problems from riding?
> Perhaps the question here is not if taller riders should be using
> /longer/ cranks, but if everyone else should be using /shorter/ cranks....

That is a good question, by I think that all the folks who have knee
problems who attribute them to the wrong size cranks would have had
knee problems no matter what. As far as exercise goes, you can't get
much easier on th eknees than cycling.

Joseph

 

[[email protected]]

On Apr 30, 7:18 am, "[email protected]"
<[email protected]> wrote:
> That is a good question, by I think that all the folks who have knee
> problems who attribute them to the wrong size cranks would have had
> knee problems no matter what.

I don't think you can say "all" there. Not exactly "problems" but I
used to get a certain soreness in the knees with 172.5's that went
away when I switched to 165's-- not to "cure" the problem, either, but
to get specific for track riding when living near a track. Short
inseam, the 165's go around noticeably easier. 175's and I don't get
along at all.

The "moral of the story" from the Martin study linked to above is "use
what you like" (I believe Jim Martin used those words someplace).

IOW (IMHO) that study is excellent voodoo antidote.

It's been awhile since I looked but one study was done with one
subject, a shorter woman, producing her best power with long cranks
(177.5?) while one tall male subject did his best with cranks from the
short end of the scale. "Use what works" and if part of that is
psyche, what's wrong with that? --D-y

 

[[email protected]]

On Apr 30, 8:53 pm, "[email protected]" <[email protected]> wrote:
> On Apr 30, 7:18 am, "[email protected]"
>
> <[email protected]> wrote:
> > That is a good question, by I think that all the folks who have knee
> > problems who attribute them to the wrong size cranks would have had
> > knee problems no matter what.
>
> I don't think you can say "all" there. Not exactly "problems" but I
> used to get a certain soreness in the knees with 172.5's that went
> away when I switched to 165's-- not to "cure" the problem, either, but
> to get specific for track riding when living near a track. Short
> inseam, the 165's go around noticeably easier. 175's and I don't get
> along at all.

Yes, "all" is a bit exteme. Perhaps your soreness was mitigated by
other changes that happened in these changes to get track-specific?
Gear choice, etc. But of course, if 165's fixed the problem obvioulsy
they are right for you.


> The "moral of the story" from the Martin study linked to above is "use
> what you like" (I believe Jim Martin used those words someplace).
>
> IOW (IMHO) that study is excellent voodoo antidote.
>
> It's been awhile since I looked but one study was done with one
> subject, a shorter woman, producing her best power with long cranks
> (177.5?) while one tall male subject did his best with cranks from the
> short end of the scale. "Use what works" and if part of that is
> psyche, what's wrong with that? --D-y

I agree 100%. If someone thinks they will do better with different
length cranks, I'm sure they will do better with them!

I have this huge crazy range of lengths on my bikes, but I am
considering switching to 165's on my road bike as that is what I have
on my track bike, which is my most comfortable bike. And I have a
rather long inseam. Go figure!

Joseph

 

[[email protected]]

On Apr 28, 11:06 am, still me <[email protected]> wrote:
> Why don't we see more variation in crank lengths?
>
> Frames commonly vary form 53 to 62cm, but cranks only vary from 165 to
> 172.5, maybe 175 (commonly anyway).
>
> Are people's bodies proportioned such that the crank lengths don't
> need to vary - or is this just a cheaper way out for manufacturers? (I
> se the problem of BB height restricting the upper end).

No. Cranks don't need to vary much beyond 175 because ... there is no
reason for them to do so. It has nothing to do with rider proportions
- the arm length is there to provide leverage, and 170 or 175 mm arms
provide enough leverage that any human can propel a bike forward using
them.

There is nothing to be gained by using longer cranks because, using
175s and commonly sized gears, the bike can already be made to move
forward with very little pedal effort.

Smaller legs require smaller crank lengths as leg length gets smaller
for obvious logistical reasons. There is no opposite problem when
legs get longer.

Doug

 

[[email protected]]

On Apr 30, 3:06 pm, "[email protected]"
<[email protected]> wrote:
> On Apr 30, 8:53 pm, "[email protected]" <[email protected]> wrote:
> Perhaps your soreness was mitigated by
> other changes that happened in these changes to get track-specific?
> Gear choice, etc.

Situation was riding too hard on a weekly group road ride with limited
conditioning time. Changed only cranks, no gear changes. Might have
made a minor saddle height adjustment; if so it wouldn't have been
much at all. I experiment every once in a while anyhow, just did a
lower/raise back up and tilt change to address a sit-down area
soreness. IOW, I'm not a believer in the Magic Adjustment of
Perfection.

> But of course, if 165's fixed the problem obvioulsy
> they are right for you.

I wasn't looking to "solve a knee problem", at all. Just to get
specific for track riding, which was my best option, due to time
constraints, to do some racing. (Just trying to get the picture
transmitted, here) The soreness I was having was pretty mild, so was
not a problem I was real worried about, although I'm glad to have it
gone. That was years ago, BTW, and since then we've moved to a
location that has lots of hills, unlike Houston,where the track was.
So, I'm climbing and putting more strain, in some ways, on the knees.
The old "problem" seems to be completely gone.

> I have this huge crazy range of lengths on my bikes, but I am
> considering switching to 165's on my road bike as that is what I have
> on my track bike, which is my most comfortable bike. And I have a
> rather long inseam. Go figure!

Well, if you had a powermeter of some sort, you could compare what's
what with the different lengths you have. When I read "only 5%
difference" over a huge range of crank lengths, that sounds fine for
more casual riders like me (currently) but if I were racing even for
odd-looking waterbottles and size XXXXL bike shorts (I did find a
donee for those), I'd want to use the cranks that gave me the most
power. Now I'm concerned with comfort. --D-y

 

[[email protected]]

On Apr 30, 11:42 pm, "[email protected]" <[email protected]>
wrote:
> On Apr 30, 3:06 pm, "[email protected]"
>
> <[email protected]> wrote:
> > On Apr 30, 8:53 pm, "[email protected]" <[email protected]> wrote:
> > Perhaps your soreness was mitigated by
> > other changes that happened in these changes to get track-specific?
> > Gear choice, etc.
>
> Situation was riding too hard on a weekly group road ride with limited
> conditioning time. Changed only cranks, no gear changes. Might have
> made a minor saddle height adjustment; if so it wouldn't have been
> much at all. I experiment every once in a while anyhow, just did a
> lower/raise back up and tilt change to address a sit-down area
> soreness. IOW, I'm not a believer in the Magic Adjustment of
> Perfection.
>
> > But of course, if 165's fixed the problem obvioulsy
> > they are right for you.
>
> I wasn't looking to "solve a knee problem", at all. Just to get
> specific for track riding, which was my best option, due to time
> constraints, to do some racing. (Just trying to get the picture
> transmitted, here) The soreness I was having was pretty mild, so was
> not a problem I was real worried about, although I'm glad to have it
> gone. That was years ago, BTW, and since then we've moved to a
> location that has lots of hills, unlike Houston,where the track was.
> So, I'm climbing and putting more strain, in some ways, on the knees.
> The old "problem" seems to be completely gone.
>
> > I have this huge crazy range of lengths on my bikes, but I am
> > considering switching to 165's on my road bike as that is what I have
> > on my track bike, which is my most comfortable bike. And I have a
> > rather long inseam. Go figure!
>
> Well, if you had a powermeter of some sort, you could compare what's
> what with the different lengths you have. When I read "only 5%
> difference" over a huge range of crank lengths, that sounds fine for
> more casual riders like me (currently) but if I were racing even for
> odd-looking waterbottles and size XXXXL bike shorts (I did find a
> donee for those), I'd want to use the cranks that gave me the most
> power. Now I'm concerned with comfort. --D-y

Yet another reason I need a power meter! And I use XXXXL shorts! Which
lap is the prime? ;-)

Joseph