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Discussion Starter · #1 ·
Seeing that the crank arm length thread is closed, probably for the irrational trolling and flaming, I wanted to post some practical experience I have with crank length. Hopefully this does not open a can of worms...

I have both 170 and 165 cranks and my PRACTICAL and PERSONAL experience has been the following:

- I do feel the difference, even if they blindfolded me.

- The shorter cranks do spin more easily, but as such put more stress on the cardiovascular system.

- The shorter crank length might force you to shift down on climbs or against headwind, whereas, with the longer cranks, you maybe could have mashed the bigger gear just long enough to get over the top of the hill or untill the next corner to get out of the wind.

- The longer crank length allows you at times to use a slightly higher gear, but has implications on your RPM's.

- The longer cranks keep your cardiovascular system steady, but might put more strain on your muscles.

- The human body has a very high degree of adaptability. I ride the different crank lengths every week and after a couple of kilometers, you quite get the hang of it.

WHICH IS FASTER?

- It isn't possible to give a rational explanation to this as I believe weather plays a much bigger role on the speeds I develop on my training circuit than crank length. I would probably prefer the shorter cranks on a windy day and the longer cranks for climbing.

- I personally think that there is probably a sweetspot between the pros and cons of every crank length in the range of 170-175 for most riders, hence industry standards tend to offer most availability of cranks in those lengths.

- I believe that much of this is related to RPM's and that again, there might be a zone of healthy RPM's for most people comprised between 70 and 90, i.e. not taking into account extreme situations such as sprints or climbs. I do think that lately "spinning" quickly has probably been overrated by some. There are disadvantages to this as well: it wears down the body, and unless one has a super (or doped) engine, it might not be the most efficient way to ride. Mashing big gears then again may cause injuries or leg cramps.

- It seems having a constant style of pedaling, gently turning circles is more important than the RPM's one develops.

ABOUT SADDLE HEIGHT.

- Again, I know from experience that a difference of 5mm can be felt and even lead to injuries in certain cases.
 

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Discussion Starter · #4 ·
For SS, I would think that 165mm has its advantage, because your leg pace changes continually. On a road bike, gears can make up for changes in resistance.

Anyway, I just hope people are less biased against different crank lengths. I think it is mainly a personal thing. I ended up trying the shorter ones because of a knee injury and I have no regrets. I do enjoy riding the normal length cranks also now my knee is back to normal.

IMO, people should go with what works for them and staying injury-free is probably the most important thing in any sport. You don't improve much by sitting at home with ice packs. For certain people shorter cranks can certainly alleviate knee problems and once they get used to it, they won't even notice the change anymore.

One can only lament the limited availability of different crank length, especially from a certain prestigious brand. Whereas it might be true that 170-175 caters to most, there are also many shorter people (many women are getting into road biking) and taller people that could respectively be served by 165 and 180 cranks.
 

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Discussion Starter · #9 ·
blackjack said:
http://le-grimpeur.net/blog/archives/18

The intention was to get the 1.73-cm tall Hinault sitting further back but also higher. As such, his saddle height was raised from 72.8 cm to 73.5 cm, but gradually over a 3-year period from 1979 to 1982 to as not to place too much strain on him, particularly his knees (Greg LeMond also endorsed this higher riding position).

Unfortunately, during one stage of the 1983 Vuelta, his saddle was accidentally set at 74 cm, and this exacerbated the strain on his right knee, which had been causing him trouble since 1980 and he had dropped out of that year’s Tour because of it. In the summer of 1983 it was operated on, causing him to miss the Tour for that year.
The new riding position was partially to allow Hinault to climb better in the saddle. He had a reputation for pushing large gears while climbing, often out of the saddle for long stretches, which was attributed by some as the cause of his knee problem.
This was a sensitive issue for Hinault and he maintained that he always had a smooth cadence, but that he would “choose his gears according to the pedalling cadence that suits me – above this cadence I get out of breath too quickly; below it, my muscles are too contracted”. For him, that optimal cadence was between 70 and 90 rpm, a fairly generous range.


I see this thread got started after the other closed. My POV is that a lot of this stuff is very subjective and I'm of the opinion that going from a 172.5 to 175 crank is not all that much of a difference. Blindfolded I don't know whether I could detect a difference.

I'm 175 cm tall and have an 85 cm inseam which would necessitates a 75 cm saddle height according to the LeMond .883 x inseam formula. I like my saddle lower though so I can ankle a decent amount. I wear a 45 or 46 shoe and have strong lower legs.

I prefer a saddle height of around 73.5 to 74. I could ride 75 but the saddle feels like it's weighted too much and down around 73 I feel my knees are too flexed but I think I could ride the lower height rather than the higher one if I was forced to choose the extremes.

Could I tell the difference in a blindfolded test, between saddles .5cm difference? If I had a direct comparison, yes, most likely, but if I just got on a bike with an unknown .5 cm increase/decrease, I might sense something was slightly off.

It's interesting in the article that Hinault went from a 54.5cm top tube to a 56.5 cm tt. The article doesn't mention the STA but the 55cm Seat tube KG381 I'm riding has an approx 56.5tt. That would be considered a big bike nowadays.

By contrast Contador is riding a 52 Specialized with 53.7 cm tt.
Critical measurements

Rider's height: 1.77m (5' 10")
Rider's weight: 62kg (137lb)
Saddle height, from BB (c-t): 748mm
Seat tube length, c-t: 490mm
Head tube length: 120mm
Top tube length: 537mm
Total bicycle weight: 6.80kg (14.99lb)
Blackjack, thanks for the link. About not noticing crank length differences, I tend to agree with you that anyone would be hard pressed to notice a 2.5mm difference. But I can share the following story about noticing 5mm changes. There is a static bike at the gym nearby my work, where I sometimes do some intervals. BTW, that machine has a mean program called random, a mode where it will throw any junk at you when you least expect it. But anyway, I noticed that my RPM's on that machine where higher and to still my curiosity, I wrote a mail to the manufacturer of the machine. Guess what, the cranks were 165mm and at that time I had only one road bike with 170mm cranks. So I guess in a way, that is a blindfolded test, as I really did not know how long the cranks were. In all honesty, it took my a couple of months before beginning to wonder. I also got into problems when trying to emulate the high RPM's on the static bike on my road bike that had longer cranks. That, coupled with a questionable cleat mount and other sports I practice at the same time got me a knee tendonitis that kept me away from cycling for more than a month.

Now I have two bikes, one with 165's and the other with the 170 cranks I already had before the injury and I ride them both, but the riding style is different. IME it is not a good idea to try to spin to hard on the longer cranks. Spinning smoothly at reasonable RPMs, yes, but overdoing it, no.

As to saddle height, with the new cranks and also with the new saddle I bought I had to determine my saddle height again. So I went for a ride, armed with wrenches and hexagonal keys to fiddle around until I hit my sweetspot and at one point I wanted to go a little higher, so I moved the saddle by what could not have been more than 5mm and as soon as I got on it I could feel that it was too high and lowered it immediately.

I also remember a ride about a year ago that I had set my saddle too high and I really had to get off the bike 10k before the finish. That is when I decided higher isn't always better.

Recently, I did the bikefit calculation at competitivecyclist.com and I get a saddle height from them around between 77 and 80cm, but I think my saddles are around 75-76, depending on the bike (different geometries and cranks). I don't even know exactly how high my saddle is set, I do know that it is the best for me, as when I set saddle height, I try different positions and pick the best one for me.

The more I think about it, the more I am convinced that there is no such a thing as a universal bike fit, or an ideal top tube length or crank length. I think it really depends on the individual's body and preferences. I changed my stem from 110mm to 100mm on one of my bikes and I can swear it feels a lot better to me. The other bike has a longer top tube, so I put a slightly shorter stem on it (90mm) but for some reason I feel I wouldn't be bothered by an extra 10mm on that bike, probably a lot has to do with geometry.

I indeed think that small details such as stem length, and cleat position, can make a big change in the end, but that depends on riding style and prefererences, as well as on physical constitution. What you say about feet length is absolutely true, a longer foot might have another way of pedaling than a shorter one and therefore cleat position and even crank preferences might be different from a shorter foot.
 
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