chummdizzle

Please don't hate me for starting a thread about crank length

I'm 5'11, and have a 37 inch in seam, 19 inch femur (not sure if I measured it right), 42.5 shoe size. I use 175mm cranks, standard and compact.

I'm having trouble climbing. I can't seem to keep my RMP's up high enough to climb effectively. I feel like I'm struggling to turn the cranks over, even with compacts. Would shorter cranks 172.5 help with this since I would be able to spin higher cadence? or do I just need to train harder?

ericm979

Shorter cranks mean that you need to put out more force to move the cranks the same speed with the same gear... basic leverage. They make it harder to turn the cranks over at a given speed and gearing.

What you need is lower gearing. Less weight, or better conditioning would help, but take time and work.

scirocco

Change down a gear.

bigfred 

If you're having trouble maintaining effective climbing cadence, around 70, shorter cranks are not going to help. They will simply reduce the amount of leverage you legs have for pushing your smallest gear. My first two responses would be, more training and lower gearing.

You see shorter cranks on track bikes and other high rpm applications because they open up the top end of the cadence range, 120+. Track sprinters in particular need to use a gear low enough that they can accellerate and then need eye popping cadence at the top end to keep it going. By going to shorter cranks they sacrifice leverage for a shorter circle radius, which they should be able to spin faster.

On the flats, I can spin my 180's just fine at 110-120. On a grade, if I start slowing below my normal 90, it's cause I'm not strong enough or don't have a low enough gear and has little to do with the length of my cranks.

JTGraphics

What kind of gears are you running now you didn't say

urbanknight

I always thought LONGER cranks helped with climbing due to the extra leverage. Don't most mountainbikes come with longer cranks than road bikes?

lukewall

go with that option.

chummdizzle

I'm running a 50/36 with a 11-26 cassette.

Ya I figured I just need to concentrate on climbing more (I've only really been riding for about 6 months). It doesn't feel like I lack the strength to turn over the cranks, but it feels like the movement is too long and like I'm loosing power on the upstroke. Which is why I thought the shorter cranks would help, since the smaller radius would keep my muscles more engaged . But I guess with my inseam 175mm would be the ideal crank length for me.

nitropowered

5'11 wiht a 37" inseam?

recursive

You're analyzing too hard and riding too soft. Stop with the internet and start with the bike. The climbing will better.

daxr

Longer cranks do give you more leverage for (in theory) more power climbing. If I remember my history right, Merckx was one of the first to use 180 mm cranks in post WWII racing, and I think he had them made for him.

You get more leverage but its harder to spin, so its usually a bad trade off. I've considered them, as I have longer legs and love to climb more than anything, but the deciding factor is bottom bracket height - I just don't have enough on my current road bike, or my last one.

bigfred 

Yep. Gold Star for you.

chummdizzle

Yes, i have literally no torso and excessively long limbs

grolby

Crank length is an endless source of ignorance. It's pretty simple: longer cranks are equivalent to running a lower gear (what do you think "increased leverage" amounts to?), and shorter cranks are equivalent to running a higher gear. The size range that most cranks are available in doesn't make enough difference to have a material effect upon gearing - and besides, if you have really long cranks, you can just gear up, or vice versa if you have really short cranks. The primary reason for choosing one length of cranks over another should be comfort. If you feel weak and crappy on 165 mm cranks, by all means ride 170s. If you feel like you're unable to get a good spin with 170s, go shorter. Whatever. One size or another is not universally better than the others for climbing, sprinting, spinning, etc. One size will be optimal because it fits you best for the combination of your physiology and needs. I would climb like crap on 180s, increased leverage be damned.

chummdizzle

I know your right. I was just offered a trade for some gear I'm selling for a Record CT 172.5 and I'm probably just trying to find a reason to get em.

As a note. I did one of the hardest climbs in my area today (Oahu, Hawaii). I had to stop once, but I finished it. So I'm not just sitting around I am trying to do something about it.

JTGraphics

I have a range of gearing, Cranks are road crankset 53/39 172.5mm and compact crankset 50/34 175mm and 12-23, 12-25 and 12-27 10 speed cassettes.
My combos are on flats and rollers 53/39 w/12-23 with short climbs in the 14% range 53/39 w/12-25 or 12-27 on longer climbs into the 17% range 50/34 w/12-25 or 12-27

JTGraphics

Suggest a 34 small ring with that 11-26

ok_commuter

You have crazy long legs like I have crazy long arms. Longer crank, bigger gear. And ride more.

I always thought bench press was easier for people with shorter arms than me. Maybe that's why (I think) I'm a good climber, even when I'm mostly a ****** - short fireplug legs easier for climbing than long ones?

ok_commuter

But if he has a short torso and really long legs, he'll probably need to ride at least 175 (depending on other factors, but assuming the seat height and bike size are relatively normal) to be comfortable AND create efficiency, right? (I.e. comfort == power)

I mean, I'm 1" taller than him and have barely 34" inseam. I have short legs, but he has really long legs. I ride 175 pretty comfortably, though I have 172.5 on all my bikes. I know it's not as big a deal as gearing, seat height and other stuff, but... crank length matters, correct?

I've lately seen a couple 180 on ebay and CL. Got no use for that, but maybe our OP does?

gregf83 

Not really correct. Changing the crank length has no effect on the power required to go up a hill at a given cadence. A longer crank will require less force but you have to push it further around the circle so no change in the work done in one pedal revolution.

Changing to a lower gear on the other hand reduces the amount of power required for a given cadence making it easier to go up the hill albeit at a slower pace.

Ratfish

Pix

ok_commuter

chummdizzle

haha, maybe later. Length from my belly button to collar bone is only 14 inches, so ya I do have a short torso

chummdizzle

HAHA ya I'm gumby

CrimsonKarter21

Analyze it all you like; if you're having trouble climbing, the problem is you, not the equipment.
Climbing is a real equalizer, if the good climbers are on $600 bikes, and the decent and mediocre climbers are on $6000, the good climbers will still climb faster.