phtomita

I went from 170 to 165mm and when R7000 came out. I got the 160mm and like it very much.
I have a commuter with 165mm and I end up pedaling slower than the other bike with 160mm where normally I try to keep 80 to 90 rpm.
I am planning on changing the commuter bike to 160mm as well, so won't have this diff from both bikes.

easyupbug 

I have now switched two bikes to 165mm from 172.5 and 175 and now believe it has helped my rheumatoid arthritis in a knee headed for major work. At 72 no danger of me flexing a bottom bracket.

PeteHski

The recommendations are based on the kinematics i.e. range of motion rather than torque/cadence. It follows that someone with longer legs can spin longer cranks with the same joint angles. Torque can be compensated for with gearing, although people rarely adjust their gearing when changing crank length. As you are a high torque/low cadence rider you just require the appropriate gearing, regardless of crank length (which you would choose based on your leg length and range of knee/hip range of motion).

What most studies I've read have concluded is that the industry standard crank lengths (170-175 mm) are generally a bit too long for many people and especially people with short legs! If you happen to be around 6ft tall with average proportions, then you are likely to be fine with standard cranks, otherwise shorter cranks are likely to be an advantage. I know two very experienced fitters who both recommend shorter cranks for many of their customers, either because they have shorter legs than a typical 6 ft guy or they have a limited range of joint movement (injury or age-related), or both! It's just another parameter in the bike fit jigsaw.

livedarklions

Again, I'm the outlier who cruises at 53x11, so from my standpoint, compensating for a reduction in crank length would require some rather exotic crank/cassette combo or an increase in cadence. Since I'm unlikely to do that, I would need a very strong reason for shrinking the crank length. I don't have unusually short legs and my range of motion is fine and shows no signs of deteriorating with age.

If what you are saying is that there are people who will benefit from a shorter crank, of course that's true. But I don't buy the argument that this leads to the conclusion that the industry is generally sizing the cranks too large (I don't think you said that, BTW, but a lot of fitters seem to). The people you're citing as needing the shorter crank are also outliers (short legs, limited ROM), although of a different sort than I am.

Iride01 

So maybe this whole idea of proportional crank sizing that was popularized in the 80's maybe even the 70's is just a hoax to handicap us taller people so the shorter people can compete!

<I'm being totally facetious in the comment above>

Though when I go to the sixth floor that my heart doctor is on, I use the stairs and take two steps at a time from the ground to the top. Have to get there early though so I have time to let my HR recover before they hook me up.

PeteHski

What I'm saying is that several studies I've read, along with two very experienced bike fitters, have concluded that the industry is indeed sizing cranks too long for even average sized riders and certainly shorter than average riders. If you are interested then have a read of this article:-

https://bikedynamics.co.uk/FitGuidecranks.htm

"Unsurprisingly, the only height at which there is any sort of agreement between the Industry Standard and recommendations is around 180cm or 5'11". As a rule the recommendations are nearly always shorter than the actual crank lengths fitted by most manufacturers! You will note that there is good agreement between the Machine Head calculation and the TA recommendation."

Fortunately for me I'm 184 cm tall with relatively long legs, so standard crank lengths (typically 172.5 or 175 on bikes in my size) are well matched.

livedarklions

I'm underwhelmed by any sense of consensus on this issue or that the effects are really significant:

https://www.roadbikerider.com/cranka...up%20on%20175s.

Basically, I don't think there's anything wrong with trying smaller cranks, but if you find you don't like them, there's no solid objective reason to think you're "wrong" for not liking them and switching back.

livedarklions

If I'm climbing stairs, crank length is the least of my concerns.

Sorry, I just had to. It's a pretty good analogy.

Basically, nobody ever hurt themselves going too small, and some people could hurt themselves going too big.

Korina

The article I was referencing is here. It contains this unfortunate paragraph, written by a man with "average" proportions:

You can see where it falls apart; you don't usually climb stairs for 10 to 50 miles and more in a day.

PeteHski

The main reason why shorter cranks are recommended is to avoid potential injury/fatigue from excessive joint motion. As your link suggests, crank length doesn't appear to have any signficant affect on your max sprint power.

My own personal experience running a limited range of 165-175 mm cranks on various bikes is that I've never really noticed any obvious difference.