Crank Arm Length

Joe Dewberry said:

I am a fairly novice Roadie and am wondering what is the criteria
for choosing crankarm length?

Whatever works best for you. There's a certain amount of trial and
error involved. One rule of thumb is 20% of your inseam, at least as
a starting point. Most people ride 170s or 175s without any trouble.

"Joe Dewberry" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Group,

I am a fairly novice Roadie and am wondering what is the criteria for
choosing crankarm length?

TIA,

I'll take a crack at this. I've read some stuff on this over the years and
it seems to boil down to:

Shorter cranks are good for track racing where the key is to be able to spin
a high cadence. In some cases, track racers spin a VERY high cadence and in
some cases, they use VERY short cranks ... as short as 155 (maybe shorter?).

Longer cranks mean more leverage. If your riding hilly road courses or
difficult terrain on a mountain bike, you'll probably want to lean more
towards 175mm cranks. If I'm not mistaken, these are pretty much standard
on mountain bikes.

The "average" road bike comes with 170 mm cranks. That's what the average
rider on the average course usually wants. Some say the ideal crank length
is tied to femur length and a taller rider should consider a longer crank.

FWIW, I'm only 5'7" and I've got pretty short legs relative to my torso.
But I live in an area with lots of hills and I like to really hammer a big
gear up the short steep ones. I've found a slightly longer crank suits me.
I use a 172.5. My best training buddy is exactly my same height, but we're
built quite differently. He's got legs up to his neck. He decided he
wanted something he could turn over more quickly to help him spin more. He
just bought new 165 mm cranks.

It's a pretty expensive component for trial and error. I hope this gives
you some direction. Good luck.

Bob C.

Joe Dewberry said:

What is the criterion for choosing crank lengths?

Looking at crank lengths available, you'll notice that nearly all are
170 or 175mm, 180mm and 165mm being way out. Short cranks are used
mainly by track riders who turn extra high revolutions or people under
5'2" height. Long cranks are used by people who naturally ride a
lower but more forceful cadence, something that becomes apparent after
many miles of tiding and good conditioning.

As far as I can see the equation says larger riders should use longer
cranks... BUT because they have larger heavier leg, they should use a
shorter crank. The upshot is that unless you are extra tall and pedal
naturally at unusually low cadence with higher than average force,
you'll do fine with 170 or 175mm cranks.

Since there are two effects opposing one another, the span of useful
lengths are limited by human muscular response to two lengths. Of
course there are those +-2,5mm sizes but they are oddities. There
will always be those who see themselves as outside that range and
demand to use shorter or longer cranks but unless you are an
experienced rider and have a known effective pedaling rate, you should
probably start with the cranks that come with the size of bicycle you
bought... if it is a high performance bicycle. I can't guess what a
Wallmart bicycle would have.

I doubt that there is a simple answer beyond that. Ride bike and then
make specific choices.

Jobst Brandt
[email hidden]

Joe Dewberry said:

Group,

I am a fairly novice Roadie and am wondering what is the criteria for
choosing crankarm length?

Half the length of your thigh, apparently, but it's almost impossible to
find where you measure to/from so this is pretty useless. If you're of
average height 170mm is OK, but if you're over 6' then 172.5 or 175mm
may be more comfortable. If you're below 5'8" or you tend to spin fast,
try 165s.

<< I am a fairly novice Roadie and am wondering what is the criteria for
choosing crankarm length? >><BR><BR>

There really isn't one. Put three people in a room and ask about crankarm
length, get 4 opinions. Talk to yer riding buddies or a few knowledgable people
at the bike shop.

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"

Joe Dewberry said:

I am a fairly novice Roadie and am wondering what is the criteria for
choosing crankarm length?

*cough* You mean "are", or "criterion".

Unless you are of very unusual height, start with 170s because they are
readily available; then if you feel uncomfortable, you can consider
experimenting with different lengths. Don't try to fix something unless
you know it's broken...
--
David Damerell <[email hidden]> Distortion Field!

David Damerell said:

Joe Dewberry said:

I am a fairly novice Roadie and am wondering what is the criteria for
choosing crankarm length?

*cough* You mean "are", or "criterion".

Oh, dear, another US-UK battle over grammar -- especially plurals.
Actually, David is right, of course. But we 'Merkins are often confused
with this particular issue due, originally, to our governmental structure
and our identification as a single country. Hence the use of "The United
States is..." -- grammatically incorrect, but reflecting our view of the
US as a single country, not a bunch of states. This seems to have caused
our reference to collective nouns as singular as well ("mathematics is" as
opposed to "mathematics are"😉 and, over here, it is considered correct to
refer to any collective noun as singular. Joe just went one step further.
For real 'Merkins, it ain't a plural unless it has an s at the end -- and
often not even then....

Quoted message said:

Unless you are of very unusual height, start with 170s because they are
readily available; then if you feel uncomfortable, you can consider
experimenting with different lengths. Don't try to fix something unless
you know it's broken...

I'd agree with this. Of course, if you are used to mountain biking, you
might feel more comfortable with 175s if you are of average height.

--

David L. Johnson

__o | Accept risk. Accept responsibility. Put a lawyer out of
_`\(,_ | business.
(_)/ (_) |

In article <[email hidden]>,

David L. Johnson said:

David Damerell said:

Joe Dewberry said:

I am a fairly novice Roadie and am wondering what is the criteria for
choosing crankarm length?

*cough* You mean "are", or "criterion".

Oh, dear, another US-UK battle over grammar -- especially plurals.
Actually, David is right, of course. But we 'Merkins are often confused
with this particular issue due, originally, to our governmental structure
and our identification as a single country. Hence the use of "The United
States is..." -- grammatically incorrect, but reflecting our view of the
US as a single country, not a bunch of states. This seems to have caused
our reference to collective nouns as singular as well ("mathematics is" as
opposed to "mathematics are"😉 and, over here, it is considered correct to
refer to any collective noun as singular. Joe just went one step further.
For real 'Merkins, it ain't a plural unless it has an s at the end -- and
often not even then....

You're an observant fellow, David, but you are a little off the mark
there. True 'Merkins know it ain't plural unless it has an apostrophe
*and* an s. I'll bet you dollar's to donut's.

--
Ted Bennett
Portland OR

Joe Dewberry said:

I am a fairly novice Roadie and am wondering what is the criteria for
choosing crankarm length?

In a nutshell, the crank length at which you will be most comfortable
will depend largely upon your inseam measurement (floor to crotch), and
your anticipated application.

Here's a useful tool you may want to try:

http://www.cranklength.info/crankCalc.htm

The Palm factor in IMO a good rule of thumb, although despite the fact
that I have a 78.75cm inseam, I feel most comfortable on 172.5mm for
general use (22.2 CLF). In any case, I feel it's better to go maybe a
little larger than the Palm factor where general road use is concerned,
unless you have bad joints or bad technique.

--

Joe Dewberry said:

I am a fairly novice Roadie and am wondering what is the criteria for
choosing crankarm length?

http://www.roble.net/marquis/crank.length

--
Roger Marquis
http://www.roble.net/marquis/

Roger Marquis said:

Quoted message said:

I am a fairly novice Roadie and am wondering what is the criteria
for choosing crank length?

http://www.roble.net/marquis/crank.length

The story in that web site doesn't sound convincing. What are the
reasons behind these admonishments? This is what bicycling myth and
lore is made of, some former bicycle racer pronouncing absolutes with
no supporting information.

By the information given, all BMX riders with 190 and 200mm cranks are
sure to be crippled for life. There's more to this than some absolute
numbers.

Jobst Brandt
[email hidden]

Quoted message said:

Joe Dewberry said:

I am a fairly novice Roadie and am wondering what is the criteria for
choosing crankarm length?

Roger Marquis said:

http://www.roble.net/marquis/crank.length

It isn't that formulaic.

Try a different length if you are so inclined. Reasonable
men differ in this.

The downside is dramatically overstated in that opinion
piece. Why?

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Quoted message said:

http://www.roble.net/marquis/crank.length

This is what bicycling myth and
lore is made of, some former bicycle racer pronouncing absolutes with
no supporting information.

No, these rules of thumb are a result of working with many coaches
and riders over 3 decades, across 3 continents, in thousands of
events, and seeing how they perform in competition with different
crank lengths.

Sad that those with no coaching or racing experience dismiss such
large sample populations as "myth and lore" without presenting any
support for their own opinions.

--
Roger Marquis
http://www.roble.net/marquis/

<[email hidden]> wrote in message
news:[email hidden]

Quoted message said:

Joe Dewberry said:

What is the criterion for choosing crank lengths?

Looking at crank lengths available, you'll notice that nearly all are
170 or 175mm, 180mm and 165mm being way out. Short cranks are used
mainly by track riders who turn extra high revolutions or people under
5'2" height. Long cranks are used by people who naturally ride a
lower but more forceful cadence, something that becomes apparent after
many miles of tiding and good conditioning.

How do you measure the crank arm length? Is it from the centres of each
bolt hole to the other?

--

A: Top-posters.
Q: What is the most annoying thing on Usenet?

Quoted message said:

How do you measure the crank arm length? Is it from the centres of each
bolt hole to the other?

I believe it's the distance from the pedal axis to the BB axis. For
straight cranks, this is the same thing.

--
Benjamin Lewis

Thyme's Law:
Everything goes wrong at once.

Roger Marquis writes:

http://www.roble.net/marquis/crank.length

Quoted message said:

Quoted message said:

This is what bicycling myth and lore is made of, some former
bicycle racer pronouncing absolutes with no supporting information.

Quoted message said:

No, these rules of thumb are a result of working with many coaches
and riders over 3 decades, across 3 continents, in thousands of
events, and seeing how they perform in competition with different
crank lengths.

There you have it. "Believe me. Just look at my credentials." I
prefer to quote a man who was good at explaining such things in
understandable terms and with substantive evidence (Richard Feynman):
"If you can't explain it in plain English, you don't understand it
yourself." I think that applies here.

Quoted message said:

Sad that those with no coaching or racing experience dismiss such
large sample populations as "myth and lore" without presenting any
support for their own opinions.

Oh so sad. It drives me to tears. I think you'll find plenty of
explanation for physical phenomena in the things I write about here
and in the FAQ, usually with examples how you can test for these
effects.

Jobst Brandt
[email hidden]

DRS who? writes from cover of anonymity:

Quoted message said:

Quoted message said:

Quoted message said:

What is the criterion for choosing crank lengths?

Quoted message said:

Quoted message said:

Looking at crank lengths available, you'll notice that nearly all
are 170 or 175mm, 180mm and 165mm being way out. Short cranks are
used mainly by track riders who turn extra high revolutions or
people under 5'2" height. Long cranks are used by people who
naturally ride a lower but more forceful cadence, something that
becomes apparent after many miles of riding and good conditioning.

Quoted message said:

How do you measure the crank arm length? Is it from the centres of
each bolt hole to the other?

Center-to-center, pedal to crank spindle, also known as crank length.

So who is DRS and why the secrecy?

Jobst Brandt
[email hidden]

Roger Marquis said:

Sad that those with no coaching or racing experience dismiss such
large sample populations as "myth and lore" without presenting any
support for their own opinions.

And sad that those who depend on the superiority of "wisdom" and
reject factual data when it contradicts the wosdom of the ages. For
example, Greenspeed recently compared cranks ranging from 150 mm to
175 mm and found that there is a slight advantage to long cranks at
low speeds and a slight disadvantage to long cranks at high speeds.
They compared heart rate vs. road speed with different length cranks.
I haven't seen the raw numbers or the full discussion of the data,
just a brief discussion in _A to B Magazine_. But it shows an
interesting correlation with similar results published several years
ago by Lennard Zinn.

Tim McNamara said:

Quoted message said:

Sad that those with no coaching or racing experience dismiss such
large sample populations as "myth and lore" without presenting any
support for their own opinions.

And sad that those who depend on the superiority of "wisdom" and
reject factual data when it contradicts the wosdom of the ages.

Wisdom? Wosdom? I think not. I'm talking about the performance
of competitive cyclists, don't know what you're talking about here
Tim.

Quoted message said:

example, Greenspeed recently compared cranks ranging from 150 mm to
175 mm and found that there is a slight advantage to long cranks at
low speeds and a slight disadvantage to long cranks at high speeds.
They compared heart rate vs. road speed with different length cranks.

Advantage as measured by heart rate, what good is that? Unless
their HR data was part of a multi-factorial analysis (ANOVA) which
included the race results of a large number of competitive cyclists
it's no more than garbage-out.

Problem is, heart rate is not an accurate measure of performance
(see <http://www.roble.net/marquis/coaching/hrm> and
<http://www.cptips.com/hrmntr.htm>😉.

--
Roger Marquis
http://www.roble.net/marquis/