Re: Time trial crank arm length 172.5 vs. 175

carlfogel@comcast.net

On Jun 23, 8:34*pm, cycledogg <cycled...@hotmail.com> wrote:
> Hello,
> *I did a search on this question thinking it may have been talked
> about already, but didn't find any results. It's a simple question as
> to building a time trial bike. Should a longer crank arm length (175)
> be used or keep the current size I am using on my road bikes of 172.5?
> I understand that a longer arm may give me better leverage to turn the
> crank but only a 2.5 mm difference is not going to be a factor. I am
> going to use larger rings (55x42). Thanks to all that give helpful
> answers.
> Cheers,
> Rick in Tennessee

Dear Rick,

An email asked me about this, probably because I posted some simple
numbers a long time ago, so I'm cross-posting to RBT.

Short answer, probably no perceptible difference.

A longer crank lowers the overall gearing, but 175/172.5 = 1.0145,
less than a single tooth on your front ring (55/54 = 1.0185).

In terms of fit, most riders from 5'4" to 6'4" use 160 to 180 mm
cranks. This means that their crank length varies less
(proportionally) than their height.

76/64 = 1.1875
180/160 = 1.1250

In other words, the riders probably adapt to the crank length.

In previous threads, some posters have claimed exquisite sensitivity
to 172.5 mm versus 175 mm (or versus 170 mm) cranks, saying that the
longer crank makes their knees hurt.

Other posters have admitted riding with the "wrong" size cranks (175
mm instead of 172.5) or even with mismatched cranks (172.5 on one side
and 175 on the other), which is hardly surprising, given that most
people have somewhat insensitive legs of slightly different lengths.

Assuming that your legs are fully extended at the bottom of the pedal
cycle, the larger crank means that you raise your feet 2.5 mm higher
with the 175 mm crank and wave them that tiny distance further forward
(and backward). So you could hunker down a tenth of an inch further
with the smaller crank.

You could experiment by having someone swap a few cranks and seeing if
you notice the difference.

Cheers,

Carl Fogel

John Forrest Tomlinson

On Tue, 24 Jun 2008 00:13:42 -0700 (PDT), carlfogel@comcast.net wrote:


>
>Dear Rick,
>
>An email asked me about this, probably because I posted some simple
>numbers a long time ago, so I'm cross-posting to RBT.
>
>Short answer, probably no perceptible difference.
>
>A longer crank lowers the overall gearing, but 175/172.5 = 1.0145,
>less than a single tooth on your front ring (55/54 = 1.0185).
>
>In terms of fit, most riders from 5'4" to 6'4" use 160 to 180 mm
>cranks. This means that their crank length varies less
>(proportionally) than their height.
>
> 76/64 = 1.1875
>180/160 = 1.1250
>
>In other words, the riders probably adapt to the crank length.
>
>In previous threads, some posters have claimed exquisite sensitivity
>to 172.5 mm versus 175 mm (or versus 170 mm) cranks, saying that the
>longer crank makes their knees hurt.
>
>Other posters have admitted riding with the "wrong" size cranks (175
>mm instead of 172.5) or even with mismatched cranks (172.5 on one side
>and 175 on the other), which is hardly surprising, given that most
>people have somewhat insensitive legs of slightly different lengths.
>
>Assuming that your legs are fully extended at the bottom of the pedal
>cycle, the larger crank means that you raise your feet 2.5 mm higher
>with the 175 mm crank and wave them that tiny distance further forward
>(and backward). So you could hunker down a tenth of an inch further
>with the smaller crank.
>
>You could experiment by having someone swap a few cranks and seeing if
>you notice the difference.

Dear Carl,

Do you have any experience (particularly successful experience) in
coaching racers or in racing yourself. Not necessarily at a high
level, but at least advising riders who beat their peers or beating
your peers yourself.

If not, please dont' dispense advice.

Cheers,

thefronny@gmail.com

On Jun 24, 4:18 am, John Forrest Tomlinson <usenetrem...@jt10000.com>
wrote:
> On Tue, 24 Jun 2008 00:13:42 -0700 (PDT), carlfo...@comcast.net wrote:
>
> >Dear Rick,
>
> >An email asked me about this, probably because I posted some simple
> >numbers a long time ago, so I'm cross-posting to RBT.
>
> >Short answer, probably no perceptible difference.
>
> >A longer crank lowers the overall gearing, but 175/172.5 = 1.0145,
> >less than a single tooth on your front ring (55/54 = 1.0185).
>
> >In terms of fit, most riders from 5'4" to 6'4" use 160 to 180 mm
> >cranks. This means that their crank length varies less
> >(proportionally) than their height.
>
> > 76/64 = 1.1875
> >180/160 = 1.1250
>
> >In other words, the riders probably adapt to the crank length.
>
> >In previous threads, some posters have claimed exquisite sensitivity
> >to 172.5 mm versus 175 mm (or versus 170 mm) cranks, saying that the
> >longer crank makes their knees hurt.
>
> >Other posters have admitted riding with the "wrong" size cranks (175
> >mm instead of 172.5) or even with mismatched cranks (172.5 on one side
> >and 175 on the other), which is hardly surprising, given that most
> >people have somewhat insensitive legs of slightly different lengths.
>
> >Assuming that your legs are fully extended at the bottom of the pedal
> >cycle, the larger crank means that you raise your feet 2.5 mm higher
> >with the 175 mm crank and wave them that tiny distance further forward
> >(and backward). So you could hunker down a tenth of an inch further
> >with the smaller crank.
>
> >You could experiment by having someone swap a few cranks and seeing if
> >you notice the difference.
>
> Dear Carl,
>
> Do you have any experience (particularly successful experience) in
> coaching racers or in racing yourself. Not necessarily at a high
> level, but at least advising riders who beat their peers or beating
> your peers yourself.
>
> If not, please dont' dispense advice.
>
> Cheers,

Right on. I would never take advice from someone who told me to swap
cranks but didn't say if I should grease the tapers. What a cop out.

tf

Tom Kunich

<thefronny@gmail.com> wrote in message
news:49863ca8-ee39-4573-8d32-c956993bfc4e@t12g2000prg.googlegroups.com...
> On Jun 24, 4:18 am, John Forrest Tomlinson <usenetrem...@jt10000.com>
> wrote:
>> On Tue, 24 Jun 2008 00:13:42 -0700 (PDT), carlfo...@comcast.net wrote:
>>
>> >Short answer, probably no perceptible difference.
>>
>> Do you have any experience (particularly successful experience) in
>> coaching racers or in racing yourself. Not necessarily at a high
>> level, but at least advising riders who beat their peers or beating
>> your peers yourself.
>>
>> If not, please dont' dispense advice.

Yeah Carl, being able to add two and two together successfully (and
correctly) isn't nearly as important as having ridden in a pack of drooling
racers in a criterium.

Robert Chung

On Jun 24, 3:18*am, John Forrest Tomlinson <usenetrem...@jt10000.com>
wrote:

> Dear Carl,
>
> Do you have any experience (particularly successful experience) in
> coaching racers or in racing yourself. * Not necessarily at a high
> level, but at least advising riders who beat their peers or beating
> your peers yourself.
>
> If not, please dont' dispense advice.

I don't coach others and my own racing career was marked both by its
brevity and lack of success but I don't think these necessarily
disqualify one from dispensing advice. I think the real issue is that
Carl appears clueless about TT'ing.

dustoyevsky@mac.com

On Jun 24, 2:13*am, carlfo...@comcast.net wrote:

> In previous threads, some posters have claimed exquisite sensitivity
> to 172.5 mm versus 175 mm (or versus 170 mm) cranks, saying that the
> longer crank makes their knees hurt.

165's compared to 172.5's in my case, and your sarcasm is misplaced.
Or, let's just say I personally know better than to listen to your
advice or opinion on this subject <g>.

> You could experiment by having someone swap a few cranks and seeing if
> you notice the difference.

Done... But, freely admitting that once I put the 165's on the road
bike, done only to "go specific" in my "training" for track racing
(where 165's are the usual fare, if not as universally chosen as they
perhaps once were), and my almost-always ("always", but I won't claim
perfection here!) sore-in-a-certain-way knees weren't sore in that
very unpleasant manner after one intense ride, and never developed
that particular pain again (maybe two or three "reminders" in eight or
nine years hence, but never the same deal), I wasn't in the least
tempted to slap the ol' 172.5's back on just to see if I could make
the long-gimpy knee joints hurt again.

Forgive me, I would have dosed a volunteer subject with ulcer-causing
bacteria (H. pylori I think they call it) while the issue was in
doubt, rather than myself, too <g>. I guess I'm just not one of those
"anything for science" type of guys.

Speaking of science, Andrew Coggan, Shaun Wallace, James Martin would
be a few names to google the group for. Medals, championships,
exercise physiology doctorates (published research) there.

<http://www.bases.org.uk/newsite/cyclingsig.asp> for one quick grab I
(confessing) didn't read but seemed like it might be OK.

Mr. Wallace posted an interesting story here some years ago IRT an ill-
chosen (as it turned out) change (IMS, 2.5mm difference) in crank
length as it affected his performance in a velodrome race. --D-y

joseph.santaniello@gmail.com

On Jun 24, 9:13*am, carlfo...@comcast.net wrote:
> On Jun 23, 8:34*pm, cycledogg <cycled...@hotmail.com> wrote:
>
> > Hello,
> > *I did a search on this question thinking it may have been talked
> > about already, but didn't find any results. It's a simple question as
> > to building a time trial bike. Should a longer crank arm length (175)
> > be used or keep the current size I am using on my road bikes of 172.5?
> > I understand that a longer arm may give me better leverage to turn the
> > crank but only a 2.5 mm difference is not going to be a factor. I am
> > going to use larger rings (55x42). Thanks to all that give helpful
> > answers.
> > Cheers,
> > Rick in Tennessee
>
> Dear Rick,
>
> An email asked me about this, probably because I posted some simple
> numbers a long time ago, so I'm cross-posting to RBT.
>
> Short answer, probably no perceptible difference.
>
> A longer crank lowers the overall gearing, but 175/172.5 = 1.0145,
> less than a single tooth on your front ring (55/54 = 1.0185).
>
> In terms of fit, most riders from 5'4" to 6'4" use 160 to 180 mm
> cranks. This means that their crank length varies less
> (proportionally) than their height.
>
> * 76/64 = 1.1875
> 180/160 = 1.1250
>
> In other words, the riders probably adapt to the crank length.
>
> In previous threads, some posters have claimed exquisite sensitivity
> to 172.5 mm versus 175 mm (or versus 170 mm) cranks, saying that the
> longer crank makes their knees hurt.
>
> Other posters have admitted riding with the "wrong" size cranks (175
> mm instead of 172.5) or even with mismatched cranks (172.5 on one side
> and 175 on the other), which is hardly surprising, given that most
> people have somewhat insensitive legs of slightly different lengths.
>
> Assuming that your legs are fully extended at the bottom of the pedal
> cycle, the larger crank means that you raise your feet 2.5 mm higher
> with the 175 mm crank and wave them that tiny distance further forward
> (and backward). So you could hunker down a tenth of an inch further
> with the smaller crank.
>
> You could experiment by having someone swap a few cranks and seeing if
> you notice the difference.
>
> Cheers,
>
> Carl Fogel

All that is true, but I think the main issue with crank length does
not have anything to do with leverage and changes in gearing.

Power is force at pedals times speed of the pedals. The pedal speed is
determined by cadence and crank length (and thus distance travelled
for given time). These things can be changed independently by choosing
how hard to push, how fast to spin, and which gear to be in. All these
variables can be independently changed while riding. That is to say
any of these things can be as fast, slow, hard, or soft as the riders
wishes to maintain some given power level.

What cannot be changed totally independently is angular velocity of
joints, and related muscle contraction rates. For some combination of
the variables above, the angular joint velocity and muscle contraction
rate will be determined by the crank length and the rider's leg
length. So to change the angular joint velocity and muscle contraction
rates for a given power and cadence (force and speed), the only way to
do it is to change the crank length (or leg length, which people
effectively do when they toe-down in certain circumstances).

I think muscle type, leg length, and personal preference dictate what
length is optimal. Determining what is optimal is a different story.

It is my opinion that knee problems that have been attributed to crank
length are actually problems that stem from positioning issues brought
about by the different length. Whether that is true or not, or even
matters, I don't know.

I use 195's on my TT bike. Does it help or hurt? Who knows.

Joseph

Paul G.

On Jun 24, 7:46*am, "travis.ha...@gmail.com" <travis.ha...@gmail.com>
wrote:
>
> A prominent proponent of long cranks is Lennard Zinn,
>

Short cranks too. He offers them from 130 mm to 220 mm. He says they
should be proportional to your inseam, which makes sense:
"Try multiplying your inseam (in millimeters) by 0.21 or 0.216 to get
a range of crank lengths appropriate for you."

He has a lot of info on crank length from various sources on this
page, scroll down:
http://www.zinncycles.com/cranks.aspx

Note that he's 6' 6" tall, and was a member of the National Team in
1980. I'm not quite that tall, but I sure was happy when I replaced
my stock 170mm cranks with some 180's (longest available back then).
According to his formula I should try some 200's.

From what I've read, it sounds like the pros use longer cranks in the
mountains and for things like hour record attempts. Here's a table of
famous pros and their crank lengths (can't vouch for the accuracy):
http://www.bikeforums.net/archive/i...p/t-128549.html
-Paul

dustoyevsky@mac.com

On Jun 24, 1:16*pm, "Paul G." <carb...@egine.com> wrote:

> From what I've read, it sounds like the pros use longer cranks in the
> mountains and for things like hour record attempts. Here's a table of
> famous pros and their crank lengths (can't vouch for the accuracy):http://www.bikeforums.net/archive/i...p/t-128549.html

Well, there's one guy on that list, a notable Hour man, who allegedly
didn't use long cranks for his record.

Or, maybe proportionally, he did. Maybe we could ask... --D-y

Tom Kunich

"Scott" <hendricks_scott@hotmail.com> wrote in message
news:dfac8a1b-3a87-4d13-93a1-610c3d9fee45@k37g2000hsf.googlegroups.com...
>
> Whether or not a particular height is optimal is one thing, but I can
> tell you unequivocably that I can tell a difference between 1 or 2 mm
> changes in my saddle height, not only in 'feel' but also whether or
> not I will have knee pain following a ride on too low or too high a
> saddle. If I were to move my saddle from my preferred position by 5mm
> either way, I'd develop knee pain within a mile unless I were just
> noodling along at about 100 watts worth of power to the pedals.

You cannot detect 1 or 2 mm since that is about 0.1% of the distance from
the saddle to the pedal. The human body has a difficult time detecting
anything smaller than 2% variations successfully.

M-gineering

Tom Kunich wrote:

> You cannot detect 1 or 2 mm since that is about 0.1% of the distance
> from the saddle to the pedal. The human body has a difficult time
> detecting anything smaller than 2% variations successfully.
>

Stick your 175 mm wide skull in a 178.5 and a 171.5mm wide opening and
please report back
--
/Marten

info(apestaartje)m-gineering(punt)nl

Michael Press

In article
<b6835c45-319a-4347-9f53-e329f80c1765@i76g2000hsf.googlegroups.com>,
"dustoyevsky@mac.com" <dustoyevsky@mac.com> wrote:

> On Jun 24, 2:13*am, carlfo...@comcast.net wrote:
>
> > In previous threads, some posters have claimed exquisite sensitivity
> > to 172.5 mm versus 175 mm (or versus 170 mm) cranks, saying that the
> > longer crank makes their knees hurt.
>
> 165's compared to 172.5's in my case, and your sarcasm is misplaced.
> Or, let's just say I personally know better than to listen to your
> advice or opinion on this subject <g>.
>
> > You could experiment by having someone swap a few cranks and seeing if
> > you notice the difference.
>
> Done... But, freely admitting that once I put the 165's on the road
> bike, done only to "go specific" in my "training" for track racing
> (where 165's are the usual fare, if not as universally chosen as they
> perhaps once were), and my almost-always ("always", but I won't claim
> perfection here!) sore-in-a-certain-way knees weren't sore in that
> very unpleasant manner after one intense ride, and never developed
> that particular pain again (maybe two or three "reminders" in eight or
> nine years hence, but never the same deal), I wasn't in the least
> tempted to slap the ol' 172.5's back on just to see if I could make
> the long-gimpy knee joints hurt again.
>
> Forgive me, I would have dosed a volunteer subject with ulcer-causing
> bacteria (H. pylori I think they call it) while the issue was in
> doubt, rather than myself, too <g>. I guess I'm just not one of those
> "anything for science" type of guys.
>
> Speaking of science, Andrew Coggan, Shaun Wallace, James Martin would
> be a few names to google the group for. Medals, championships,
> exercise physiology doctorates (published research) there.
>
> <http://www.bases.org.uk/newsite/cyclingsig.asp> for one quick grab I
> (confessing) didn't read but seemed like it might be OK.
>
> Mr. Wallace posted an interesting story here some years ago IRT an ill-
> chosen (as it turned out) change (IMS, 2.5mm difference) in crank
> length as it affected his performance in a velodrome race. --D-y

Mr. D., you are a scholar, a philanthropist, and a gentleman.
I would never set CF straight on a matter, preferring to see
him continue as a Mr. Rogers with delusions of Samuel Clemens
dispensing bad advice.

--
Michael Press

Tom Kunich

"M-gineering" <ikmotgeenspam@m-gineering.nl> wrote in message
news:g3rnr9$q23$1@localhost.localdomain...
> Tom Kunich wrote:
>
>> You cannot detect 1 or 2 mm since that is about 0.1% of the distance from
>> the saddle to the pedal. The human body has a difficult time detecting
>> anything smaller than 2% variations successfully.
>
> Stick your 175 mm wide skull in a 178.5 and a 171.5mm wide opening and
> please report back

Marten, what exactly does that have to do with estimating lengths that can't
easily be detected without measuring devices? Is it your impression that you
can tell if your saddle is 1 mm (0.04") different in height? What about
double that?

My saddle height is 39" or 990 mm - if you really believe that I could tell
whether my saddle height was off by 2 mm I wonder just how sensitive your
senses are.

carlfogel@comcast.net

On Tue, 24 Jun 2008 23:13:03 +0200, M-gineering
<ikmotgeenspam@m-gineering.nl> wrote:

>Tom Kunich wrote:
>
>> You cannot detect 1 or 2 mm since that is about 0.1% of the distance
>> from the saddle to the pedal. The human body has a difficult time
>> detecting anything smaller than 2% variations successfully.
>>
>
>Stick your 175 mm wide skull in a 178.5 and a 171.5mm wide opening and
>please report back

Dear Marten,

Humorous, but Tom is talking about detecting a range of motion for an
ankle-knee-hip joint, not about forcing solid bone into tight places.

A better test would be to ask someone blindfolded to detect the
difference when his thumb and little finger are spread 6.9 or 7.0
inches apart.

At some point, depending on the size of the hand, even the tenth of an
inch extra distance may be noticeable because the stretch will start
to hurt, just as some riders may notice after some riding that a small
change in crank length makes their knees sore.

Cheers,

Carl Fogel