# 175mm cranks to 177.5mm, who has done it?



## ralph1 (May 20, 2006)

Hi all,

Has anyone gone from 175mm cranks to 177.5mm, and did you notice any benifit?

Pros - cons?

cheers

Pete


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## perpetuum_mobile (Nov 30, 2012)

I am 6'4 so 177.5 does not seem extreme to me. I have been riding with 172.5, 175 and 177.5. Currently I have 177.5 on my winter bike and 172.5 on my racing bike. 
I can ride 177.5 on my winter bike comfortably only because it has a more upright and relaxed geometry.

I used to have 177.5 for a short while on my racing bike which has a very aggressive geometry. 177.5 feels very nice when you are pedaling out of saddle or when riding uphill. On the flats 177.5 felt very "powerful" for the first 40-50 miles but then I got sore and my back started hurting. After 100 mi ride with 177.5 it also took several days for the soreness to go away. With 172.5 I can ride 100+ miles several days in a row and I never get sore and no back pain ether.

I think that your flexibility, core strength and riding position are the most important factors that will determine which crank length is right for you. I suggest that you don't follow any kind of "formulas" or "advice" on the internet. Everyone is different and there is no way that someone other than yourself can determine what is right for you. Just try different lengths.


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## JackDaniels (Oct 4, 2011)

I tried it, didn't like it and went back to 175. Even though I think it might have been in my head, because I can't believe 2.5mm is enough to notice.

It probably just a matter of preference, I have a 36" inseam and I know people of similar height who prefer to run 180mm cranks.


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## woz (Dec 26, 2005)

It is doubtful you'd notice a difference unless you were already having knee issues on the 175, then you may find more problems on the 177.5.

The old school of thought was that longer cranks produce more leverage. However newer studies have failed to be able to show any difference in performance based on longer crank lengths. One study I know of that was done by a pro tour team and is not public was unable to show any advantages to longer cranks for their tested riders. However they did find that there were gains in positioning and aerodynamics from the shorter cranks with no measurable losses in power or leverage. Needless to say all the tested riders ended up racing with shorter cranks the following year.


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## nhluhr (Sep 9, 2010)

I'd be curious what the various cycling inseam and femur/thigh lengths are noted for people using longer cranks.

I have always used 175's on all my bikes but am strongly considering going to a longer crank.

Height 6'3", Cycling inseam 36", femur 19"


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## Kerry Irons (Feb 25, 2002)

nhluhr said:


> I'd be curious what the various cycling inseam and femur/thigh lengths are noted for people using longer cranks.
> 
> I have always used 175's on all my bikes but am strongly considering going to a longer crank.
> 
> Height 6'3", Cycling inseam 36", femur 19"


The "logic" of "crank length should be proportional to leg measurements" has been around for a LONG time, and lots of people have turned that "logic" into a formula for determining crank length. Only one problem: the research doesn't support it. One key feature that is often ignored in these discussions is the duration of muscle contraction that is controlled by cadence. It just may be that there is an optimum here, which is why there is a fairly narrow range of cadence for optimum performance. Longer cranks tend to mean lower cadence, moving you out of that optimum range. Crank length has been a point of debate since the introduction of the "safety" bicycle in the late 1800s, and there have been all sorts of fads in that regard.

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.


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## bigbill (Feb 15, 2005)

I've been on 175's for the past 22 years. I have a set of 177.5's that I used for time trialing in the 90's with 44/54 rings. I liked them but unless I build a TT bike, they gather dust. I'd like to use them again this year, I liked the way they felt pushing a big gear on a course with rolling hills. Wouldn't want them for daily rides.


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## perpetuum_mobile (Nov 30, 2012)

> I'd be curious what the various cycling inseam and femur/thigh lengths are noted for people using longer cranks.
> 
> I have always used 175's on all my bikes but am strongly considering going to a longer crank.
> 
> Height 6'3", Cycling inseam 36", femur 19"


How about trying 172.5 or even 170? Longer does not mean better. I am 6'4 and 172.5 works the best for me. I don't get sore on the long rides and recover much faster.


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## wim (Feb 28, 2005)

woz said:


> The old school of thought was that longer cranks produce more leverage.


I agree that longer cranks make no difference in performance. But longer cranks producing more leverage was never just a "school of thought." A longer crank is, in mechanical fact, a longer lever. One of the reasons it gains you nothing is that a 2.5 mm increase in crank length results in a 7.8 mm increase in the crank circle's circumference. This means that at the same leg speed, you need more time to complete the crank circle. From there, it gets even more complex: the crank is only lever 1 in a force-flow chain of four levers, with chain wheel radius, cog radius and wheel radius being the other three.


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## adam_mac84 (Sep 22, 2010)

I changed... notice very little difference, aside from more pedal strikes (took 2 CX races to change my form a bit on cornering). I have had a good season on the 177.5 on my race bike, so will keep them. I have 175 on everything else. Don't notice a big difference when switching. I think switching between my 2 pairs of shoes has a bigger difference becuase of an insole in my foul weather shoes vs my 'race' shoes.


Its all in my head, but I am ok with that. I like how my bike is set up

I would think that the fact that I have 20 gears will cover any perceived change in leg speed, cadence etc, because if they are going slower than i like, i shift... too much leg speed or spinning, i shift.

Ryan trebon has gone between 177.5 and 175's on his CX race bikes over the years, i bet if it were that big of a deal, he'd make sure to work a deal to keep him on 177.5 (some manufacturers/sponsors do not offer them)


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