# Crank Arm Length Question



## clarkna (Dec 6, 2008)

Hi ladies/gents, had a new bike for ~11months and feel 175mm long crank arms are too long for my leg length, making high cadence work i used to find easy difficult. As a rough guide I'm ~174cm tall with pretty normal body dimensions. Could you please leave your height and crank lengths to give me an indication of what people are using? Cheers.


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## guddis (Nov 14, 2008)

190cm and 175mm


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## Andrea138 (Mar 10, 2008)

166cm and 172.5mm


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## wim (Feb 28, 2005)

Asking people's height and crank length might not help you much. For one, your question assumes that riders have experimented with different crank lengths and then settled on the one perfect for them. Your other assumption is there's a clear relationship between body height, crank length and ability to spin. There isn't.

Now, negating everything I said above, I'm 178 cm tall and have always been happy with 170 mm cranks.


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## ncvwnut (Oct 15, 2008)

http://www.peterwhitecycles.com/fitting.htm

this may give you some info on crank size for you. I have a 170mm crank and 165cm tall. I like how this paper explains things and it gives a much more non-scientific way to fit. Each person with the same exact dimensions may not like an exact same set up.


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## heathb (Nov 1, 2008)

I've experimented with different crank arms from short to long.

170, 172.5, 175, 177.5, 180, 185 

I'm 188cm and like the 175. 

For me the longer arms are too much for greater distances. 

I actually like the 172.5 arms as well, but I sold those off. The spin is indeed more comfy with a shorter crank arm. However I felt like I could put more power into the 180, but after awhile they were too much. 

What lenght of arms do track cyclists use. I'm guessing shorter because it's a fixed gear and you don't want your pedals stricking the track, but what about faster accelerations with a shorter crank arm?

In the end use what is comfy for you and forget about all this nonsense about manning up to the challenge of using longer arms.


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## wim (Feb 28, 2005)

heathb said:


> What lenght of arms do track cyclists use. I'm guessing shorter because it's a fixed gear and you don't want your pedals stricking the track, but what about faster accelerations with a shorter crank arm?.


Depends on the event. Match sprinters generally use shorter cranks because they often slow down to walking speed or even come to a complete stop during the race. If they're up on the banking and slow down, they need to lean _into_ the banking to stay upright. That, in turn, can cause them to dig the _uphill_ pedal into the track. Track pursuit and time trial riders ride different crank lengths, just like road riders. There's no clear faster (or slower) acceleration with shorter cranks—it's more about power over weight.


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## andresmuro (Dec 11, 2007)

clarkna said:


> Hi ladies/gents, had a new bike for ~11months and feel 175mm long crank arms are too long for my leg length, making high cadence work i used to find easy difficult. As a rough guide I'm ~174cm tall with pretty normal body dimensions. Could you please leave your height and crank lengths to give me an indication of what people are using? Cheers.


almost 5.8. 31.5 inch inseam. 170.

My problem is not with cadence but with lower back. When I bring my knee up, a long crankarm increases the acuteness of the angle between my hamstrings and lower back. This leads to lower back discomfort during long rides. More than 3 hours. 

Longer crankarms increase your leverage on the downstroke. But only barely and it is hardly perceptible. You could also increase leverage by moving your cleat forward. OTOH, it also makes the pedal circumference bigger making it more difficult to pull up and making your lower back angles more acute. 

In studies, they found that there appears to be no relationship between length and speed. However, I haven't' heard studies about long time on the bike and longer crankarms, where the bigger circumference could lead to discomfort.


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## vlckx (Mar 4, 2005)

203 cm/180mm


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## Cory (Jan 29, 2004)

6'4" (don't feel like doing the conversion to mm) and 175. Every bike I've owned but one has come with 175s, so that feels normal to me. FWIW, though, I briefly owned a garage sale Campy-equipped Motobecane that came with 170s, and while I loved every aspect of it except the cranks, I always felt cramped and restricted. I could spin like a b**tard, though.


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## DrSmile (Jul 22, 2006)

I'm 5'6" and I have 2 busted knees from skiing. I can't ride anything longer than 172.5 or risk excruciating pain after a couple of hours on the bike. 3 years ago I switched all my bikes to 170 and it's been smooth sailing since.


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## jorgy (Oct 21, 2005)

164cm height + 79cm inseam = 170 cranks


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## MR_GRUMPY (Aug 21, 2002)

188cm. All bikes with 175's
When I changed over to 175's, it took a month to be able to spin like I could with 172.5's.
If I had unlimited funds, I might try some 177.5's, seeing that I have a few months to get used to them.


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## Creakyknees (Sep 21, 2003)

I've been using 172.5 for years (5'11") but the new bike has 175s. I just finished my second ride on it 76 miles with a group, and I really felt comfortable and was spinning along nicely. FWIW.


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## Peanya (Jun 12, 2008)

Doesn't crank length matter in terms of your leg bone length and fitness level vs height?


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## iliveonnitro (Feb 19, 2006)

height: 172cm
inseam: 84cm
crank length: 170mm


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## z rocks (Sep 9, 2007)

6' inseam 32"
172.5 rd. Easier to spin or so i've heard.
175 mtn. Better leverage for grunting up steep stuff. I swear i feel that extra 2.5mm.


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## bicicletă (Aug 18, 2008)

165cm height

175mm SS MTB
170mm Road


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## ProRoad (Oct 13, 2008)

5-10" = 177.8 centimeter

MTB 175
road 172.5
track 170

These numbers derived at The Olympic Training center so they work for me. But maybe not you.

Gotta try a bunch out

I got dropped on the Simi ride today so maybe I should switch.


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## clarkna (Dec 6, 2008)

ncvwnut said:


> http://www.peterwhitecycles.com/fitting.htm
> 
> this may give you some info on crank size for you. I have a 170mm crank and 165cm tall. I like how this paper explains things and it gives a much more non-scientific way to fit. Each person with the same exact dimensions may not like an exact same set up.


Thanks for your replies people. This article is pretty interesting. I think a shorter crank will do the job. Leg position is pretty spot on at bottom dead centre, but at top dead centre thigh to shin angle is a lot less than 90 degrees, resulting in no power for a long period on either side of top dead centre for the flexing leg. One post noted larger pedal arc diameter for longer cranks, which increases time spent at bottom and top dead centre, which I think kills high cadence riding (especially when hill climbing, due to constant decelleration of the bike due to gravity which requires constant smooth power output).

Also, Since Power=Torque*rpm, where torque is force rider puts in*distance from crank axle, a longer crank will deliver more torque for the same force, resulting in better acceleration, which another reply noted. Guess it depends on what you want. For me, being a slightly built rider with low force (sastre etc), high rpm is necessary to maintain the same power output as a high force rider (Ulrich) at low revs, so high RPM with a shorter crank length is what I'll be chasing!!


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## rizz (Aug 8, 2007)

I'm 5' 10" and went from 175 to 170 then to 172.5 and couldn't tell a difference between them. Just for what it's worth.


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## Mr. Versatile (Nov 24, 2005)

199.5 - 175


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## brucew (Jun 3, 2006)

Height: 180cm, 70.875"
Inseam: 87cm, 34.25"
Crank: MYOB
Crankset: 175mm

My first bike had 170s. It always felt like baby steps. I felt like I couldn't get full power from my legs since I couldn't get them high enough at the top to get good extension. That bike also had platform pedals I was forever lifting my feet right off them at the top of the stroke.

I put 175s on my second bike and immediately felt right at home with them. Just that extra inch at the top was all I needed. Oh, and my typical average cadence falls between 90 and 95 rpm and on most rides I max at 108 to 112.


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## danl1 (Jul 23, 2005)

Lennard Zinn makes custom cranks in a bunch of sizes. Take it for whatever you will, here's his take on the topic :

http://www.zinncycles.com/cranks.php


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## heathb (Nov 1, 2008)

So the conservative formula for determining proper crank arm lenght would be:

Inseam in inches which would be 34inches..... convert it to mm which would be 863.6mm.

Then multiply 863.3mm by .21(the conservative percentage according to zinn) would give me 181.93mm crank lenght arm.

I would assume that for safety reasons I would use a 180mm arm since that is what is more available and less risk to my knees.

Inseam can be measured with a book between the legs shoved tight up into your crotch standing barefoot on a hard floor, measure to the top of the book.

I currently use 175 and have another bike set up with 177.5 and I can tell a difference in power(increase) and a slight decrease in cadence with the longer arm. The comfort level is greater on the short arms when I'm riding in the drops.


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## heathb (Nov 1, 2008)

How about everyone on this forum give us your inseam measurements and lets see if we should all be using longer crank arms according to Zinn.


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## heathb (Nov 1, 2008)

*I stole this from another forum. I have no idea who originally came up with this, but it seems to be good way of explaining the difference in crank lenght between 170 to 180 or 10 mm difference........*

Longer cranks will give you the same effect as LOWER gearing. What you want to compare is the total distance the pedal-spindle moves per revolution vs. linear-distance the bike moves. It's the ratio of bike-distance to pedal-spindle distance that's the leverage-ratio.

The other way to compare leverage-ratio is instantenous linear velocity of the pedal-spindle vs. the linear velocity of the tire's outermost edge.When you say lower gearing, you are referring to a numerically lower ratio, correct? Which would indicate a 'taller' gear.

In other words, switching to longer crank arms has the same effect as switching to a larger chainring; less PPM for a given speed (linear distance covered) with a subsequent decrease in mechanical advantage (higher effort.)

Is this correct? This would be my assumption.No, it's the other way around (the chain is not attached to the pedal BTW). Taller gears are harder to push. So going from 52x15t -> 52x13t is going into a taller gear (harder to push). Going from 170mm cranks to 175mm cranks is like going into a lower gear, like 52x13t -> 52x14t (easier to push). Here's how it works out mathematically:

170mm cranks = 107cm circumference (pedal's motion per revolution)
52x13t gear = 0.250:1 = 862cm travel per crank-rev = 0.124:1 pedal-to-travel ratio
52x14t gear = 0.269:1 = 800cm travel per crank-rev = 0.133:1 pedal-to-travel ratio
52x15t gear = 0.288:1 = 747cm travel per crank-rev = 0.143:1 pedal-to-travel ratio
38x13t gear = 0.342:1 = 630cm travel per crank-rev = 0.170:1 pedal-to-travel ratio
38x14t gear = 0.368:1 = 585cm travel per crank-rev = 0.183:1 pedal-to-travel ratio
38x15t gear = 0.395:1 = 546cm travel per crank-rev = 0.196:1 pedal-to-travel ratio

180mm cranks = 113cm circumference
52x13t gear = 0.250:1 = 862cm travel per crank-rev = 0.131:1 pedal-to-travel ratio
52x14t gear = 0.269:1 = 800cm travel per crank-rev = 0.141:1 pedal-to-travel ratio
52x15t gear = 0.288:1 = 747cm travel per crank-rev = 0.151:1 pedal-to-travel ratio
38x13t gear = 0.342:1 = 630cm travel per crank-rev = 0.180:1 pedal-to-travel ratio
38x14t gear = 0.368:1 = 585cm travel per crank-rev = 0.193:1 pedal-to-travel ratio
38x15t gear = 0.395:1 = 546cm travel per crank-rev = 0.207:1 pedal-to-travel ratio

Notice first that going from 170->180mm cranks, with just 1cm longer cranks, the path of the circumference that you push the pedal through increases by 6cm.

Also look at initial gear-reductions. The 52x13t gear reduces torque by 0.250 (1/4) in going from the crank to the rear-wheel. A lower gear of 38x15t has more mechanical leverage and reduces torque by only 0.395 times. As you shift into lower and lower gears, the mechanical leverage increases and the pedals are easier to push at the same speed. Your feet moves through a larger distance for the same wheel-revolution (you spin more), or the converse, the wheel rotates less for the same pedal-revolution.

The same effect is noticed in going to longer cranks in the same gears. Whereas the 52x13t gear with 170mm crank has an overall 0.124 reduction, the 180mm crank has a 0.131 reduction for more leverage. In fact, the 180mm crank gives about the same leverage in a 52x13t gear as the 170mm crank using 52x14t. What this means is that pushing a bigger gear 52x13t with 180mm crank will "feel" as easy as pushing a 52x14t gear with 170mm cranks. So for the same muscle-effort, you can push a bigger gear with a longer crank. Let's see how that translates into power-generated...

Given that:

power = work/time = (force*distance)/time

if you keep force from muscle-exertion on the pedals fixed, like you're already pushing as hard as you can, the only way to increase power-output is to increase either the distance that you push the pedals (lower-gears or longer cranks) or to decrease the time it takes for one crank-revolution (higher-RPMs). Let's assume that we maintain the same RPMs with both set of cranks, we can simplify the equation to:

power = (force*distance)

and let's say we're pushing on the pedal with the same force in both cases we can further reduce the equation to:

power = distance

then make a ratio of the two pedal-circumferences:

_powerA___ = __powerB_
distance107 distance113

and we end up with:

powerB = powerA*1.056

So with exactly the same RPM and exactly the same pedal-effort on both 180mm vs. 170mm cranks, the 6cm longer pedal-travel of 113cm vs 107cm gives 5.6% more power.


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## danl1 (Jul 23, 2005)

heathb said:


> How about everyone on this forum give us your inseam measurements and lets see if we should all be using longer crank arms according to Zinn.


Two for the price of one:

me: 34.5 = 184 >175. I'm confident I'd notice that, and don't think I'd appreciate it
wife: 29 = 155 <165. I'm fairly certain she'd like the change.


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## danl1 (Jul 23, 2005)

heathb said:


> So with exactly the same RPM and exactly the same pedal-effort on both 180mm vs. 170mm cranks, the 6cm longer pedal-travel of 113cm vs 107cm gives 5.6% more power.


Well, it doesn't exactly 'give' anything. That power comes from the muscles moving the legs in larger arcs. It's not as if it's free power.

Oh, and while you've inverted the ratios, your the origin of your ratio calculations is none other than The Great One.


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## Gimme Shoulder (Feb 10, 2004)

180cm and change with legs slightly short for the height. 172.5.


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## Kerry Irons (Feb 25, 2002)

*Formulas*



heathb said:


> So the conservative formula for determining proper crank arm lenght would be:
> 
> Inseam in inches which would be 34inches..... convert it to mm which would be 863.6mm.
> 
> Then multiply 863.3mm by .21(the conservative percentage according to zinn) would give me 181.93mm crank lenght arm.


Just so you know: There is no reliable formula for predicting crank length. There ARE lots of formulas out there, but they are just figments of the imagination of their purveyors. No one has ever done a study that shows how crank length should relate to anything.

You will find no high quality data to support any particular crank length as being better than any other. This is true whether or not you correct for leg length, femur length, etc. On the other hand, you will find lots of anecdotal or low quality data to support all kinds of conclusions, and more theories than you can shake a stick at. A rider's response to changes in crank length is 1) highly individual, 2) dependent on riding style and the event (TT, climbing, crits, track racing, etc.), and 3) most important, highly adaptive. This is why it is so hard to study the effect of crank length.

A 2008 study by Jim Martin, Ph.D., from the University of Utah shows zero correlation between crank length and any performance factors.
=============================
Fred Matheny Summary: There have been studies of crankarm length, but the results aren't consistent. Some show that longer cranks provide greater leverage for turning big gears. Some show that shorter cranks foster greater speed via a faster cadence. And some show that crank length is completely individual.


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## danl1 (Jul 23, 2005)

Kerry Irons said:


> Just so you know: There is no reliable formula for predicting crank length. There ARE lots of formulas out there, but they are just figments of the imagination of their purveyors. No one has ever done a study that shows how crank length should relate to anything.
> 
> You will find no high quality data to support any particular crank length as being better than any other. This is true whether or not you correct for leg length, femur length, etc. On the other hand, you will find lots of anecdotal or low quality data to support all kinds of conclusions, and more theories than you can shake a stick at. A rider's response to changes in crank length is 1) highly individual, 2) dependent on riding style and the event (TT, climbing, crits, track racing, etc.), and 3) most important, highly adaptive. This is why it is so hard to study the effect of crank length.
> 
> ...


 
Or stated alternately: This formula is as good as any other. 

There are obviously limits somewhere - try to pedal some sort of kiddie toy and it quickly becomes obvious that there's such a thing as too short. And it doesn't take any imagination at all to picture too long, even before considering the limitations of bicycle design. From there, it seems reasonable to assume that there's some sort of function that makes sense, though it's not at all reasonable to assume it's directly proportional to an anatomic measurement. But even if one could derive a formula, it would only give us a starting point. Preference, muscle composition, flexibility, fitness, and so on would have some effect on the 'ideal' answer - and no model (or no testing) could possibly sort all of that out.


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## AlexCad5 (Jan 2, 2005)

Kerry Irons said:


> Just so you know: There is no reliable formula for predicting crank length. There ARE lots of formulas out there, but they are just figments of the imagination of their purveyors. No one has ever done a study that shows how crank length should relate to anything.
> 
> You will find no high quality data to support any particular crank length as being better than any other. This is true whether or not you correct for leg length, femur length, etc. On the other hand, you will find lots of anecdotal or low quality data to support all kinds of conclusions, and more theories than you can shake a stick at. A rider's response to changes in crank length is 1) highly individual, 2) dependent on riding style and the event (TT, climbing, crits, track racing, etc.), and 3) most important, highly adaptive. This is why it is so hard to study the effect of crank length.
> 
> ...




I only really wanted to know what Kerry thought Actually, that is almost true. As always, his thoughts are sound and reasoned.:thumbsup: 
My antecdotal evidence is I couldn't really tell the difference between the power in the sizes. As a matter of fact, I rode a 170 thinking it was a 172.5 for 3 years. 
It does seem that it would be an effective way of moving the saddle back or forward, if you need an extra couple of millimeters (if you're already planning to get the new, latest greatest crankset.)


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## heathb (Nov 1, 2008)

Yeah I've combed the internet looking for answers on crank arm length and honestly there's limitless contradicitons for every theory that states longer arms will increase power.

I did come across a list of pros (TDF riders) and their crank arm lengths and was surprised that even some of the bigger guys rarely if ever went over 175. Most of the pro peloton were actually using 170 to 172.5, very few were using 177.5 and I'd doubt hardly any at all were using 185. 

Jacques Anquetil 175mm
Lance Armstrong 175mm
Magnus Backstedt 177.5mm
Chris Boardman 170mm
Santiago Botero 172.5mm
Angel Casero 175mm
Mario Cipollini 172.5mm
Fausto Coppi 171mm
Malcolm Elliott 172.5mm
Tyler Hamilton 172.5mm
Bernard Hinault 172.5mm
Miguel Indurian 180mm (190mm for second Hour record!)
Laurent Jalabert 172.5mm
Greg Lemond 175mm
Brad McGee 175mm
Robbie McEwen 175mm
Eddy Merckx 175mm
David Millar 175mm (180mm in TT)
Francesco Moser 175mm
Marty Northstein 167.5mm in Keirin (170mm in kilo)
Graham Obree 175mm
Marco Pantani 170mm (180mm in mountains)
David Rebellin 172.5mm
Roger Riviere 175mm
Jean Robic 170mm
Tony Rominger 172.5mm (175mm for Hour record)
Oscar Sevilla 175mm
Jan Ullrich 177.5mm
Rik Verbrugghe 175mm
Erik Zabel 172.5mm
Alex Zulle 175mm (180mm in mountains)

The thing I noticed when I was experimenting with crank arm length is when I went up to 180 and 185 I had an increase in leg cramps. I thought the arms felt great, but after 60 miles of fast pace riding my legs would cramp up pretty bad. The shorter arms didn't have that affect on me(didn't seem to engage as much muscle mass), but then again I didn't feel like I could really dig in when I was riding a 170 and 172.5. For me the 175 seems to be the sweet spot(compromise). Although there's always that urge to go back to the longer cranks and work through some of the cramp issues to see if I can increase my over all speed. 

Could it be that pro riders that have to ride great distances sometimes as much as 6 days a week during racing season need the shorter cranks 170 -172.5 because of wear and tear on the knees or perhaps to save energy that would be used with a longer crank.

For me the best study subjects would be professionals as I think they provide a way to find out what happens when the body is pushed to the limits everyday. They would certainly know what knee pain is if something was incompatible as far as arm length.

This is a fascinating subject, I just wish someone could produce a valid scientific study.


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## heathb (Nov 1, 2008)

From that list above of pros the one that I find most interesting is Marty Northstein 167.5mm in Keirin (170mm in kilo). I've watched clips of this beast of a man and I have to wonder. Could he use this shorter crank for longer distances or would he use something longer out on the road. 

From the view of watching him on the track the shorter arms would seem not to decrease power at all as Marty was the kind of rider(sprinter) that had tremendous speed and power. I'm sure Marty trained many miles out on the open road it would be interesting to know what he prefered as he's the same height as me, but clearly a much bigger build.


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## perttime (Jun 27, 2005)

176 cm (shortish legs, not sure about inseam)
175mm cranks on three different bikes.

I like Sheldon Brown's (RIP) take on crank length:
http://www.sheldonbrown.com/cranks.html

My picks:
"_Too long cranks cause excessive knee flex, and can cause pain/injury if it causes your knee to flex more than it is used to._"

"_I think people really obsess too much about crank length. After all, we all use the same staircases, whether we have long or short legs._"


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## heathb (Nov 1, 2008)

Yeah I've read Sheldon Browns website and have learned quite a bit.

Still he leaves me wondering since he states that the pedal to travel ratio is higher(using a longer crank arm) with 53/12t, which is not at all uncommon when you're racing.

I've often been in the highest gear and pushing as fast as I can on some shorter road races say in the 40 mile range. I look around and wonder sometimes if some of these other guys that are really powering down the road are using longer crank arms, of if they are simply turning at a higher rpm. I've also wondered this because even though I'm 6'2" I'm often on the smaller side of those in the top 10, many of those guys tend to be 6'4 to 6'6" with very solid builds. 

I use to think the answer was to put a larger set of chain rings on my bike than before to offer higher gears, but that actually failed since it took considerably more force to turn and would cause my front knees to ache the following day.


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## Mr. Versatile (Nov 24, 2005)

I have 175s on my DeRosa, and 170s on my commuter bike. I can't tell any difference when riding.


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## jmlapoint (Sep 4, 2008)

6'2"/188cm
Road = 180mm
Track = 170mm
Personal preference and what I am used to. No Science/Trial and error.


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## function (Jun 20, 2008)

6'0 / 183cm height
36" / 92cm inseam
175mm


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## HRT (Jan 2, 2009)

175cm height, 83 inseam Road 172.5mm Mtb 175mm


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## Bumblebee Man (Oct 2, 2004)

Kerry Irons said:


> Just so you know: There is no reliable formula for predicting crank length. There ARE lots of formulas out there, but they are just figments of the imagination of their purveyors. .


ha! Totally! :thumbsup: I couldn't have put it better myself


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## bikeman68 (Feb 10, 2009)

To CLARKNA and all interested:
If you are a road racer, or a serious road rider who strives for efficiency, you can follow a simple formula still the most comon in the pro peloton. This is from a French book that has input from Bernard Hinault its Road Racing.
cycling inseam 77-80 cm, for 170mm cranks
81cm -86cm for 172.5mm
87cm-93cm 175mm
I will add here, for clydsdales, 94cm to 98cm - 177.5mm. 
180mm? If you can ride Magnus Becksteds bike, maybe.


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## muscleendurance (Jan 11, 2009)

172.5 road bike (moving to 175 v soon)
168.5 on touring bike!
It doesnt matter as long as your in the right 'neighbourhood" 
just that longer =more torque/leverage
shorter='easier' spin...


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## GirchyGirchy (Feb 12, 2004)

height: 188 cm
inseam: 91.5 cm
cranks: 175 mm


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## axebiker (Aug 22, 2003)

I use 170, 172.5, and 175. I can't tell the difference from "feel", but I can spin better on shorter cranks.


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## bikeman68 (Feb 10, 2009)

Hey tech scientists
I know there have been some ridiculous methods or "formulas" for crank lengths on road bikes,I know , because the size for me was over 10mm too long! Anyhow, I want you all to have confidence in the crank size chart based on inseams in cm (crotch of rider in bike shorts to the floor, with no shoes on)
This CHART, not formula, is reliable, and consistent info based on data gathered of many European Pro riders (road racing) That book I got this from was originally written in French, and was allowing Bernard Hinault, and his sport Physiology consultants an opportunity to share important info to the public, or any serious cyclists. Getting the ideal crank length is as important as the ideal gear ratio.It can make a big difference on muscle fatigue at the end of the race, or day. Every 2mm of crank length is as important as every mm of saddle height on the bike. The info I shared is for the passionate riders who will notice if somebody messed with the saddle height and left it 1mm higher than it originally was. You do'nt have to be on a div 2 team in Europe to see these differences, and or benefits.Just being a highly trained rider, with muscle memory tells alot.
If you need a consistently really high cadence, you can follow the old school method and go 1 size (2.5mm) shorter than the chart recommends for a Criterium specialist, who sprints alot, and has no concern for big hill climbs. The other exception may be a Triathlete, who sticks to a steady 75-90 rpm cadence, and so with that style you can go 2.5mm longer to help in pushing a big gear, or just saving muscular endurance at that high effort, slower cadence riding thats typical in a TT or triathlon bike leg of the race.
Both Greg Lemond and Laurent Fignon were strong big gear pushers, and liked 175mm cranks best for road races (not just TTs) even though they were of avge height, and inseams (84.5- 85cm) This may be a good idea for Triathletes.
Mr Lance runs 175mm cranks on the rd bike, and goes to shorter 172.5mm cranks for his high spin Time trial bike, so he can keep that trademark 110 cadence.


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## flyjoe (Mar 17, 2008)

my bikes have,170, 175,and 180. It doesnt make a difference to me either way as I cant tell a difference. cadence is the same, speed is the same. But I try to stay with 175 just because I like uniformity.


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## Voodoochile (Apr 10, 2009)

I'm 5'10" but never thought height had anything to do with it. I've raced plenty of crits and RR and have always used 170mm. I asked one of the guys that's been in bike sales and racing his whole life and sold racing bikes all over the world and what he told me that for the racing I mostly do which was crits that spinning faster is my objective and for that the 170mm is my best choice. Spin to win baby!


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## Voodoochile (Apr 10, 2009)

bikeman68 said:


> To CLARKNA and all interested:
> If you are a road racer, or a serious road rider who strives for efficiency, you can follow a simple formula still the most comon in the pro peloton. This is from a French book that has input from Bernard Hinault its Road Racing.
> cycling inseam 77-80 cm, for 170mm cranks
> 81cm -86cm for 172.5mm
> ...



Well this has worked for me for 15 years because I use 170mm and my inseam is 77, but it does look like many of you guys are alot taller than average. I've never tried longer cranks but have hit pedels on the pavement many many times in races pedeling around corners and couldn't imagine using longer crank arms. One time I blew a back tire after hitting a pedel when the tire came back down on the pavement losing a race I surely would have won. I have always been true to the old stand by saying.
*"SPIN TO WIN!!!"*


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## bikeman68 (Feb 10, 2009)

*Crit cranks/ VooDooChilie*

Hey VooDoo
Do you have any videos of your racing action? Sounds like you're an awesome Criterium rider. You could'nt go any longer in crank length for road racing with your inseam. If you are that good in Criteriums and dont do any road races seriously, maybe you should look for 167.5mm road double cranks? You will get a faster top end spin in the sprints, and be able to ace the corners in a crit and make big gaps leaving the others sprinting for your wheel in frustration!
You would be a good candidate for track racing too. Good Luck
Jack


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## bikeman68 (Feb 10, 2009)

Hi Flyjoe
I can tell you with all my experience, the 2.5mm increments in the crank sizes make a difference. If you can spin a 180mm crank well, then you must be very tall, with a 64cm road bike. The 5mm jumps in crank sizes make an obvious difference to a highly trained rider, or avid road bike enthusiast.
If you really are fluid with the 180 cranks, and then go spend a month on a bike with cranks 5mm shorter, you will lose the fluidity you gain from training on the 180mm ones, so stick to one size to make the most of it, as said in Bernard Hinaults book, ROAD RACING. Good luck, Tall one


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## bikeman68 (Feb 10, 2009)

Your crank size of 172.5mm is quite common for your height. You ride a 55 or 56 cm frame probably, so right on with mid size. I doubt the 175mm cranks would help you on the hammer road ride unless you pedal very powerfully like a Lemond, or Ulrich, with a slow cadence.This will kill the legs of most mortals, pushing gears like either of these stars, along with Hinault.
Good luck, train smart!


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## Voodoochile (Apr 10, 2009)

bikeman68 said:


> Hey VooDoo
> Do you have any videos of your racing action? Sounds like you're an awesome Criterium rider. You could'nt go any longer in crank length for road racing with your inseam. If you are that good in Criteriums and dont do any road races seriously, maybe you should look for 167.5mm road double cranks? You will get a faster top end spin in the sprints, and be able to ace the corners in a crit and make big gaps leaving the others sprinting for your wheel in frustration!
> You would be a good candidate for track racing too. Good Luck
> Jack


I haven’t raced in about 4 years (I’m getting old 41 now) but I got my start racing crits about 5 miles from my house where a local bike club hosted training crits every week of the summer so I have raced many of them there and all over the midwest. I live in IL and racers came from all over the Midwest every week. I wouldn't say I'm awesome (yikes) though (average and obsessed with cycling) I just raced alot and learned many lessons.


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## bikeman68 (Feb 10, 2009)

Heath
I have seen a few radical crank formulas, and this is one of them, there is no way a guy with an avge inseam like you can pedal fast and consistently in the range of 90 rpm with a 180 crank. You should be on 172.5mm cranks with an 86cm inseam, and a 175mm crank at the longest, if you insist on a gear pushing TT cadence of 75-85 rpm.
Long cranks often detect the slightest weakness in knees, leaving the rider with mysterious pain at the front of the knees after the ride or race.They are notoriously rough on knees.


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## heathb (Nov 1, 2008)

Funny that you mentioned this bikeman68.

I actually switched out my 177.5 crank with my 170 and have been riding the 170 for about 5 weeks now. 

I did this for crits, but truthfully I kind of like the way it feels on long training rides as well. I noticed less cramping issues and no pain issues with the front of my knees when doing standing sprints. 

I think I'll keep the 170 cranks on as I see no benifit as far as speed is concerned with the longer crank arms. 

The main advantage right now is not cramping. I'm sick of cramping up the last couple of miles in a road race and having to finish 10th place over and over because of it. I've got the speed to stay until those cramps start in.


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## SystemShock (Jun 14, 2008)

clarkna said:


> Hi ladies/gents, had a new bike for ~11months and feel 175mm long crank arms are too long for my leg length, making high cadence work i used to find easy difficult. As a rough guide I'm ~174cm tall with pretty normal body dimensions.
> 
> Could you please leave your height and crank lengths to give me an indication of what people are using? Cheers.


I was in the same exact boat as you. I'm 5'10" (178cm), but I'm rather torso-y, and only have the leg length of someone about 5'8" (173cm).

I tried 175mm cranks for awhile, buying into the 'longer is better' hype. It just felt wrong from day one... too hard to spin.

Went back to 172.5mm, and it was MUCH better.

Those who say, "It's only 2.5mm, how can you feel the difference?", aren't thinking it through... a 2.5mm diff in crank length actually translates out to a 16mm difference in pedaling circle. I definitely DID feel it. 

And you couldn't make me go back to 175s.

Far as Zinn's formula for crank length goes, well, there's a LOT of formulas out there. Which is correct? Who knows. Go with what worsk for you. From what you're saying, that doesn't sound like 175s, not at your leg length. 
.


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## dd74 (Aug 2, 2007)

heathb said:


> The main advantage right now is not cramping. I'm sick of cramping up the last couple of miles in a road race and having to finish 10th place over and over because of it. I've got the speed to stay until those cramps start in.


This has been happening to me too. Could it be related to cranks that are too long?


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## heathb (Nov 1, 2008)

dd74 said:


> This has been happening to me too. Could it be related to cranks that are too long?


Depends on what crank you're using right now, but for me four things have cut down on the cramps drastically this year.

Shorter crank. Moved from a 177.5 to 170.
Moving to a cleat with float. Was using cleats with no float.
Moving cleat back and more towards the center. 
And spending a lot more time stretching everyday. 

I'll never completely get away from cramping as that's just the way my body works, but I haven't had any major cramping issues so far this year, but state championships are coming up in a month and those are the races that causes me the most hellish cramps, so I'll see how it goes.


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## merckx_rider (Aug 20, 2008)

I'm 183cm and my racing bike had 172.5mm
I use 175's on my training/commuting bikes
I have 180's on my cruiser
each has a much different ride/purpose....


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## wankski (Jul 24, 2005)

this i have experimented with... despite being crap at it i like climbing.... i've found the longer definitely helps and for me , easier to get on top of to power thru a hard pull on the level as well... i may go back.... i've been on 170, 172.5, 175...

height: 182.5cm
inseam: 33.5"
crank road (now): 172.5mm... may switch to 175 for better TT and climbing performance and feel..
crank mtb: 175mm

conversely to the accepted wisdom, when switching back to 170mm cranks, i started to feel slight knee pain at the front of the knee cap... this does not happen with the larger cranks... all q-factors the same... I feel that 172.5 is easier to spin than 175, but there is little difference... 

You also need time to accommodate a change... u may not necessarily like it at first, but difference in cadence and feel... you will adjust to it in time (week or three).

Thanks for the list of what the pros use btw.... it was instructive to me, most of those guys running 175 are about my height or shorter...


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## muscleendurance (Jan 11, 2009)

Im waiting for someone to post on the *actual* differences in power/torque output (the longer leverage arguement people talk about) what does 2.5mm diffference length on a 175mm crank do for you power wise?
its only ....calculating... about 1.5% difference in length!


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## bikeman68 (Feb 10, 2009)

*cranks*

Hey Wank
Sounds like your cycling inseam is avge, maybe 85cm? If you run 175mm for road use, you would be using the same crank fit as Lemond or Fignon, who were big stars, very strong, and pushed big gears.If you ride in a group, and want to spin in a paceline, it may be near impossible to keep a fluid spin of 100 plus rpm.
If you have a TT bike, you may want to experiment for a good 2 months with the 175s before you decide they're good for you, you need time to adapt to any size.
Normally, you are in the range of the 172,5mm cranks. 
Good Luck


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## wankski (Jul 24, 2005)

yeah thanks.... that is why i figured i'd try the 172.5s....

i was pretty settled on 175s though, i only changed when i destroyed my driveside UT bearing within about 5,000-6,000kms... had no issue spinning @ 100.

meh.. one of these days i'll get me the hollowgram crankset and just change crank arms (and spider) to suit the type of riding. God i love that crank!


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## bikeman68 (Feb 10, 2009)

Hey
If you liked the 175mm size best, and it probably does help in Mountains, and youre cadence is fast enough in a paceline where you do not need to ride all day in big gears, killing your legs and getting dropped, then 175 might be your favorite. I have long legs, about 91 cm inseam, and use the 175mm size, but I insist on a nice spin on the flats, and a more economical cadence in the hills, so thats why I use this size instead of riding a 177.5mm crank and pushing all the time.
That drive side UT bearing might have gotten abused with bike washings, maybe thats why it got pooched. Be careful cleaning the chain on the bike.


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## wankski (Jul 24, 2005)

i'm not a big fan of the UT... i'd day ur right as i wash my bike in my bath, with just the handheld shower head, and hand safe dishwashing soap... that's it... normally i'd say no biggie but the UT is so poorly sealed... i'm running the newer olive BB cup now with my 172.5, so hopefully that helps

the chain comes off for cleaning in solvent so i don't think that's it... i don't drench the thing... thing is, it died well before campy suggests servicing IIRC...


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## alexb618 (Aug 24, 2006)

165 track
170 road

5'11" inseam about 32


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## mimason (Oct 7, 2006)

My 57cm road bike has 172.5mm cranks but I just purchased a TT bike (56cm) that has 175mm cranks. The fitter told be I can push the longer crank due to it being a TT bike but that he personally does not like running two different setups. That said I rode the TT bike the other day and can tell the differences too. When I go up a bridge encline the 175mm cranks enable me to better pull up on the cranks than with my shorter road bike cranks. Obviously, I am turning a bigger circle. I have always had trouble pulling up on my 172.5 cranks while climbing in the saddle. It makes me wonder if I am better off in some respects with the longer crank...but I also may fatigue sooner pushing a bigger gear. I suspest my inseam size in smack in the middle of the two sizes at roughly 33.5-34in.

At this point I am not sure if I should ask the LBS to keep me at 172.5's or run two different crank lengths.


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## IbisFox23 (Mar 8, 2009)

5'6" using 170 for road,175 for AM MTB, and 180 for race BMX cruiser.


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## bikeman68 (Feb 10, 2009)

*mimason, extrordonare de cyclisme*

Good question
If you do road race, and do criteriums as well, and if you have a particular talent with sprinting, stay with 172.5mm on the road bike, but if you have ridden a while on 175mm cranks and can keep a good fast tempo cadence when sitting in with this longer size, and do not have much punch in a sprint where you can afford the loss of acceleration and top end leg speed, then I bet you might like 175mm better on the road bike.
Not to sound confusing, but if you feel you have a good all round ability, and can challenge others in a sprint, during a crit or road race, you may decide youre better off with a more traditional crank size that the Italians would recommend, 172.5mm.That is probably the only way to ensure you have a good fluid style that promotes the other disciplines I mention. Sprinters value a hi rpm ability very much, and is often a deciding factor with cranks.
With Time Trialing, its simpler for most, where you can go at a moderate intensity, at a steady rpm of 85 to 95-100 most of the course, unless you can mirror Lance Armstrongs style,(which is that much harder)I bet you would like the muscle saving edge of the longer crank. Only a guuy like Lance goes to a SHORTER 172.5mm crank for time trialing, as he keeps his TT RPM's at 100-120 or so!
And with all this in mind, remember that Bernard Hinault would say the only way to make the best use of ANY crank is to stick to one size.An interesting note is that Eddy Mercks (who has long legs,91cm inseam) would use 175 on the road bike, and switch to 177.5mm for Mtns and Time Trials


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## bikeman68 (Feb 10, 2009)

Again
save yourself mind boggling chatter, and see my inseam to crank length chart, divided into the 3 crank size camps, 170, 172, 175, and I even add a special piece for the Clydsdale group for inseams over 93cm.
The report from Dr Jim Martin is expected, hes a track specialist, who uses crank sizes like 167.5 or 170, so no wonder he doesnt see lactate and fatigue saving benefits in Roadies crank sizes. Every 2.5mm crank size is a noticeable difference in leverage and leg speed, so dont rule out crank changes if you fall into the fitting inseam ranges I provide in the charts based on data from the pro peloton.All the nerdy mathematical "formulas" I see are mind boggling ways to still end up with a real long crank size, way off the chart, even for gear pushers like Lemond and Fignon, and they went an extra crank size on their rd bikes, but they were also animals who could stay in a high gear all day.


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## wankski (Jul 24, 2005)

hey bikeman,

just wondering, how exactly is overall height or even an inseam instructive in crank fitting? does not femur length matter as well?

surely this is what matters the most as a proportion of overall inseam??

in any case for myself, i'm not too worried as i easily pulled a PB on my 172.5 cranks on a hilly TT. I will repair my 175 cranks tho to do a back to back test in a similar state of fitness... one of these days...


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## Davidhenderson (Mar 15, 2010)

*there is do significant difference in commerically available cranks for efficiency*

Crank length has very little effect on efficiency. Dr. James C Martin has conducted research showing this. Some of his findings are illustrated here: http://myworldfromabicycle.blogspot.com/2010/08/dude-your-crank-lengths-fine-you-just.html

(my apologies for the typo in my topic title. It should read: There is no significant difference measured with the different commercially available crank sizes concerning efficiency.)


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## Bumblebee Man (Oct 2, 2004)

Can ya do me a favour and start a thread on Bike Forums with that link? 
I'd like to see a few people with their "theories" try to tell you it's wrong


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## waldo425 (Sep 22, 2008)

6'1" 170mm and 165mm (track and at least for the time being commuter.)


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## Davidhenderson (Mar 15, 2010)

Will do.


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## bikeman68 (Feb 10, 2009)

*cranks*

you argumentative data nerds reveal how little trained you guys are as road racing or riding enthusiasts.If you just have faith in the how to and training material such as the benefit of tailoring your cranks size, and rpms (cadence) you would get somewhere if you ride with an athletic local cycling group.
If you have a sport physiologist like Dr Martin doing tests with top amateur or pro trackies, you get a much different type of power output that would show different results in ideal crank lenght (much shorter for explosive track efforts)
BUt for a strong road racer in a sustained AT effort in a breakaway or in a 40 k state TT on the road, having the ideal crank length is very important.If you switched the said riders cranks to 2.5mm shorter ones behind his back, he would feel this right away with such a highly trained and biomechanics adapted body.
Whever says cadences that lean closer to 60 rpm are most efficient really dont know cycling, or have the ability to ride with local weekend Cat 4 warriors.
If I raced in the packs with 60-80 rpms for a 100 plus mile Cat 1-3 road race, Id have never finished and blown up with wasted legs, its that important to find an optimum cadence over 80 rpm.


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## AdamM (Jul 9, 2008)

> you argumentative data nerds reveal how little trained you guys are as road racing or riding enthusiasts.


FWIW, I doubt if he'll bring it up, but one of those "little trained" "data nerds" you're debating is our current national champion. Knows a thing or two about road races.


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## bikeman68 (Feb 10, 2009)

OK, well you guys can ride whatever you choose, i was just trying to help based on my exp.The submission that suggested that their really isnt a negligible benefit to ideal crank size and cadence of at least 75 for climbing on up to 100 or 110 on the flats is just plain stubborn ignorance, not wanting to believe all that helpful advice for the avid, trained road riders or racers.
The only exception that has its own 'science" is triathlon since the riders there do things radically different such as big gears, extra crank length, slower cadence and forward saddle.
the right gears can make the difference of having the strength to win, or finish that big ride at the end of the day without blowing up on the last big hill or mtn.
Good luck to all, whatever you guys decide on doing


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## clarkna (Dec 6, 2008)

Wow, so many passionate comments!!

Just thought I'd cap off this thread (found it when deleting old emails). After 3 years of training and racing what I've found is:

Uphill sprints and high cadence training drills + strength efforts + power and speed efforts, combined to meaning if I could sit comfortably between 100-105rpm in a race with the high torque generated by using 175 cranks, I win races (have won several open state level races in australia). High rpm+high torque=high power.

Used 175's for a few years, then went to 172.5s with my new bike just to try it out. It is easier to maintain high cadence, but due to the shorter length, torque is reduced, making steep climbing harder and took the edge off sprint kicks. 

Overall, I've found both lengths have their pros and cons, which can be both worked around with specific training. Track racing at the moment on 165 cranks makes high cadence on the long cranks easy, and smooths the pedal stroke! 

Also saw a lot of debate on the ideal cadence based on studies etc. I think high cadence is absolutely necessary for repeated attacks in long road races, where quick recovery is needed. Sure there are guys that claim to be 'gear mashers' etc, which is fine, each to their own, but unless you have 55-11 chainrings, won't ever keep up at 55k's an hour in a race as they won't have the top end speed to keep up, nor the ability to accelerate quickly/change pace quickly. Maybe a tt yes, but not a race. TV can also be deceiving, in that low cadence guys are actually up around 90rpm as everyone else can spin at~105-110.

My 5c worth... cheers.


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## cda 455 (Aug 9, 2010)

clarkna said:


> Wow, so many passionate comments!!
> 
> Just thought I'd cap off this thread (found it when deleting old emails). After 3 years of training and racing what I've found is:
> 
> ...


Thanks for the update.


As for me:

186cm with 180mm crank arms.


I've used 175mm crank arms for years (Since 1975!) and then experimented with 170mm about a year ago. I felt like I was spinning on a kid's tricycle. I then put a BMX 180mm crankset on and love it. When I'm climbing I really feel I'm squeezing out more torque with each revolution with the same gearing.


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## bikeman68 (Feb 10, 2009)

Clark, you sound like a good road racer, are you a Cat 1 or 2? My French book that has input by The Badger says if your inseam is 87-93cm and want to run a size like the road pros then 175mm should be right on, and then they go on to say dont limit yourself there and try 2.5mm longer for TTs or Hill climbs. I have long legs, and ride a 59 cm bike, run 175mm for my main use on road, and for the road and criterium races.If I went longer Id lose my spin on flat land, and would pedal chopy if I tried to spin at 110-120 rpm.


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## JaeP (Mar 12, 2002)

Height: 188cm
Cranks: 180mm or 177.5
I'm not a spinner.


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## royta (May 24, 2008)

andresmuro said:


> almost 5.8. 31.5 inch inseam. 170.
> 
> My problem is not with cadence but with lower back. When I bring my knee up, a long crankarm increases the acuteness of the angle between my hamstrings and lower back. This leads to lower back discomfort during long rides. More than 3 hours.
> 
> ...


5'7" height, 31"-ish leg length, and 170mm crank arms. I'd like to try 172.5's, but don't want to spend the money. My knee would be higher at the top when using longer crank arms, and I'm not sure I'd like that when in the drops. I just completed my second full year of road riding, and it wasn't until this summer that I was able to ride in the drops on flat ground without my knees feeling they were too high, coming into my chest, and interfering with my breathing.


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