Short Cranks - Worth it or Hype?

[CyborgQueen]

I've done a little search, but it seems like they're old threads.

I own a 2009 48cm Jamis Ventura Elite - Everything is stock, except for the saddle (of course!).

I have been riding on this for nearly two years now. I'm vertically challenged, so certain things don't always fit me right like it does for most women.

I was reading up on Hill climbing (and somehow I stumbled across some of Luv2Climb's posts...dang girl! I want your climbing legs!), and to make long story short, I wonder if my cranks are too long for my legs.

My crank currently is FSA 170mm double compact, which I know is the standard crank size.

I found through the web and found a formula that measures on what's a good crank size for your leg length. Turns out that I need a 155mm crank. With a quick search, I didn't realize those sizes are difficult to find. I could go for 160mm, but 155mm is the ideal size.

However, after talking to three different cyclists - none are women fwiw.

One says that I ought to go for the smaller crank (160mm), because when I make circles with my legs, it's making a much larger circle than if I had the 160mm or smaller. I will perform better on the hills, and have much better turnovers (which got me intrigued, because I'm struggling on the hills).

The second guy says that it's not even worth it. 5-10mm is not going to make a difference. Only cycling on hills frequently will. Yet, he rides on 165mm arms and says he feels no difference.

The third guy said, "They will also help you spin a little faster. But as far as climbing, they'll actually make life ever so slightly harder. It's a matter of leverage. You're spinning the bottom bracket when you pedal, and the longer the lever from the fulcrum (your bottom bracket spindle) to your point of contact (in this case, your pedal), the more torque is applied for a given amount of downward force." So basically, if I go smaller, I will be happy, but will lose a little of leverage/torque. There's a disadvantage for the advantage.


So.....my question to you gals is (BTW - I do plan to ask my fitter as well, but I wanted more women's opinions) - Has anyone change their crank size from 170mm to 165mm (or smaller) and noticed a difference?

Thanks for any insight.

[OakLeaf]

Do you have to point your toes to reach the pedal at the bottom of the pedal stroke? Are you having calf or ankle trouble because of that? Are you having knee trouble because your knees are flexing too much at the top of your pedal stroke? Do you prefer pedaling at higher RPMs?


ETA ... your actual question was whether I noticed a difference. I'm usually better about reading posts before responding to them.

Yes. Enormous difference. Unbelievably enormous. Besides solving my knee and Achilles tendon injuries, 165s are just plain more comfortable for me.

[KnottedYet]

I'm a 175 crank kind of gal.

Riding on a 165 drives me nuts.

So, my assessment is that 1 cm is definitely enough to notice!

Not sure why you have a person telling you it will cause you trouble on hills... cuz, like, isn't that what lower gears are for? Seriously, lever arm means doodly-squat if you have the optimal gear height for the slope/effort.

In my universe, where I am Queen and the world does my bidding, crank arm seems to have a lot more to do with leg function. A leg with a longer femur would probably do a lot better with a longer crank than a leg with shorter femurs. Jammin' that chainring from hip and knee flexion to extension through the arc of greatest power is going to vary with the length of femur. (the arc is going to vary, I mean; so longer femur would love a longer crank)

Try a shorter set of cranks. Save the longer ones for just in case. Be ready to change your smaller chainring for one that is smaller yet (won't cost you more than $20 or $30) to get a smaller gear height to compensate.

[CyborgQueen]

Do you have to point your toes to reach the pedal at the bottom of the pedal stroke? Are you having calf or ankle trouble because of that? Are you having knee trouble because your knees are flexing too much at the top of your pedal stroke? Do you prefer pedaling at higher RPMs?


ETA ... your actual question was whether I noticed a difference. I'm usually better about reading posts before responding to them.

Yes. Enormous difference. Unbelievably enormous. Besides solving my knee and Achilles tendon injuries, 165s are just plain more comfortable for me.

Point my toes - no, it's parallel to the ground.
Calf/ankle trouble - no, my ankle is flexible, and hardly ever have issues.
Knees - when I go higher RPM, or when I'm in the drops - they do get a twinge of soreness due to the angle - this is where I wish it was a little bit more open.

Interesting because I've been cycling for nearly 2 years, running for a year Triathlons for a year, and not once got injured. Only calf tightness (due to running, not cycling) - and Funny enough...even after a hard bike ride, I don't need to "recover". Am I rare breed? Perhaps I'm not working hard enough!! My quads are surely SCREAMING when I do the hills. :-)


@KnottedYet - Interesting that you said that....my bike fitter did mention that I have long femurs for my size.

I already have a compact, so the only way I could go "smaller" is to get a triple, isn't it? Otherwise if I do 50/30...that's way too big of a jump for my shifters to handle.

[KnottedYet]

@KnottedYet - Interesting that you said that....my bike fitter did mention that I have long femurs for my size.

Just about every woman has "long femurs for her size."

Which is why I am constantly correcting fits that male fitters have done on my female clients... following the numbers as though they were men. Which causes trouble. Of course, my sample is biased because I'm only seeing the women who had *failed* fits and are now in pain.

(never follow numbers for a fit, always follow function!)

[CyborgQueen]

Just about every woman has "long femurs for her size."

Which is why I am constantly correcting fits that male fitters have done on my female clients... following the numbers as though they were men. Which causes trouble. Of course, my sample is biased because I'm only seeing the women who had *failed* fits and are now in pain.

(never follow numbers for a fit, always follow function!)

Good point!!! Never thought of it that way. Damn male fitters. :-) Too bad that I don't have a female fitter here.

Having a bit of saddle issues, and still working on finding "THE ONE".

[TsPoet]

On my 4 conveyances, I have
1) 165
2) 160
1) 155.

I ride recumbent, so it's a little different, on a bent your body is stuck and you can't push up and get relief (if that makes sense). So, short cranks are, I think, more important.
I'm 5'7" with a 32" inseam, so fairly long-legged.
I don't notice the difference between 170s and the 165 when I got them. When I got a bike with 160s on it - Wow! I began to spin in the 80s rather than 60s, I could go farther, climb better. My avg speed didn't change much, but I could ride farther.
My velomobile has the 155 (my choice was 170 or 155, and I wasn't going back to 170s)
The 155 really feel different, and I'm not sure I really like them. So, I'd choose 160s from now on if I can. I can spin nice and smooth and fast and I'm amazed at how easy it is to climb hills in the 65 lb velo - so maybe the short cranks have something to do with that.
I'm a huge fan of short cranks.

[TxDoc]

Yes, I do notice the difference if I happen to ride a bike with a different crankarm length. Despite being short, I always used 172.5.
Every time that I rented or borrowed bikes with 170 or 175 - I was never as comfortable as I am with the correct crankarm length.
I remember that a couple of times I borrowed a bike that had a 165, and that was a real nightmare - completely inefficient power transfer!
I'd say go see a good fitter and find out which crankarm length is best for you.
Good luck!

[radacrider]

My road bike has 170mm which have allowed me that feels just right cadence. My SUB (mtb) came with 175 and I never felt I could spin the same. Finally, I swapped it all out for 170 and I am happy, happy.

Linear measurement, yeah, it's 5mm on the radius, 10 on the diameter - but that is a lot on the circumference where your foot is moving. 175 is outside of my happy leg zone.

[Crankin]

This is a male thing to say the length makes no difference.
I had 165s on my first 2 road bikes. When I bought the bike I have now, shop owner tried to convince me I needed 170s "to unleash my inner power." Yeah, except I am a super spinner, I never stand, and I hate mashing. I generally use the easiest gear I can, that gives me enough power to do what I need to do. While I do ride in the big ring somewhat, it's never more than about 25% of the time, because it hurts my knees the next day.
The minute I hopped on the bike after it was built up, I felt the difference. Every pedal rotation was a strain and I felt like I was pushing like the bike did not fit me (it did, other than this).
I had to beg and convince the guy to order me the 165s. He knows better now. I am a short, endurance type rider in her late fifties, not a racer. I need to be comfortable.

[Rebecca19804]

This is perhaps a bigger difference than O/P asked about, but I switched from stock 170 to 160 on the advice of my fitter (with my physiotherapist present at the fitting). I am 5'4", 32" inseam but with short femurs and arthritis in my knees. When I collected the bike after the crank swap, I was initially preoccupied with other changes (esp narrower drop bars) but after a few miles I suddenly thought "hey, my knees are happy!" Now, I'd never felt "unhappy" with the 170s. But shorter cranks produce a smaller-diameter arc or circle, so the most acute angle of the knee is more open and that translates into just a bit more "ease". Kinda like loosening the waistband of your jeans after a big meal.

[KnottedYet]

But shorter cranks produce a smaller-diameter arc or circle, so the most acute angle of the knee is more open and that translates into just a bit more "ease". Kinda like loosening the waistband of your jeans after a big meal.

Beautiful description!

[MomOnBike]

For what it's worth, the doc who 'scoped my knee said that shorter cranks are a good idea for my creaky, arthritic knees.

I love my 165s