Bike pedal crank arm length for climbers ?

Has any climber+cyclist tried to determine their optimal crank length and found it to be substantially different from what would be expected for a non-climber cyclist of similar dimensions ?

Would you expect it to be different for a climber/cyclist of the same dimensions vs just a cyclist?

Most casual cyclists likely don’t even know their crank length, never mind their ideal length. I’m sure nearly all just run whatever came on their bike. 

Yeah I was thinking climbers have more flexible hips.

(I would agree with anybody who accuses this topic of majoring in the minors, but I'm still curious)

I rode for decades on 172.5. I got a mountain bike with 165 a couple years ago. It’s awesome. If I ever want to replace cranks on even my road bikes, it’ll be under 170 for sure.

As for what that’s got to do with cycling. Pretty much nothing. You’d be hard pressed to make an argument to convince there’s any correlation.

You should ride the longest cranks your knees will tolerate. Levers are good. But essentially no one makes cranks longer than 175 anymore.

Also move your seat back and put on a longer stem. There, now you’ve used your hip flexibility. 

I’d agree that climbers most likely have greater hip mobility than cyclists, but the degree to which a cyclists lack of mobility inhibits them using longer cranks is questionable in my opinion. As mentioned previously many mountain bikers are going towards shorter cranks, I believe Hope even makes some 135mm cranks which admittedly are marketed towards e bikes. But nonetheless 165mm cranks are becoming more and more common on trail bikes where they used to be reserved for DH. I suspect this has less to do with hip mobility and more to do with making use of the silly huge range that cassettes have nowadays. 175mm cranks paired with a 32t ring and 52t cass is enough to go rock climbing with your mountain bike if you had the traction. 

I think the main reason cranks have grown shorter on mountain bikes is to prevent pedal strikes with compressed rear suspension, and now that many bikes have shorter cranks, people are realizing, hey, these work pretty well, maybe I'll try them on the road, too. 

Over the years, this topic always comes up, with different profesionals and individual experienters trying long cranks (180 mm plus) or short cranks (below 165 mm).  To the extent that such research takes place (fairly limited) there are various studies out there supporting one view or another.  

Leonard Zinn, of Zinn cycles, believes in cranks proportional to height and leg dimensions, and points out that options on the market are severley limited--if one really wants to have cranks be proportional to the body.  He sells cranks in a wide range of lengths to support his custom frame and bike bussiness. 

Back to the OP...what are you talking about?  Mountain bike?  Road?  Time trial?  Climbing?  Sprinting?  Touring?   Triathlon?  

Your body position and (perhaps) your optimal crank length might vary for all of these.  

If you want to see what longer or shorter cranks do for you, buy some cranks in different lengths and try them.  1) Put them on your bike, 2) Get on a stationary trainer with a power reading and a heart rate monitor, 3) Ride at a consistent power output for some set time interval, and repeat with different length cranks, 4) See if your heart range is higher/lower/the same.  Bear in mind that this could change depending on the power output, ie a lower power outputs cranks of one length might be the most effecient, and at higher outputs cranks of another length might be optimal.  

As for the "hip mobility" question, unless you're talking about a really compressed time trialing position (which is often different from a triathlon position) your hip mobility shouldn't really be a problem or an influential factor.  If you seat is so low, or your upper body so extended, or your cranks so long, that you are having difficulty bringing the pedals over the top of the stroke, then something's wrong...but the best time trialists sometimes train themselves to produce higher power outputs in these constrained positions.  

To simplify, it probably makes sense to just go with a "regular length."  In todays world that's probably 165-170 for mountain bikes, and 170-175 for road bikes.

Cranks have been trending shorter for years now, more recently in mtb. Like Bruno says, it helps a bit with rock strikes, but I like them for spinning a nice pedal stroke. Also, it’s good when they use smaller cranks on small bikes for people like my five foot tall wife, for whom 170s are ridiculous. No idea about the cyclist/ climber comparison. 

Listen to HAFE. He used to be a good rider. Personally, before I stopped racing, I switched from 172.5 to 170 on all of my bikes due to a right hip issue. I thought my climbing and time trialing would suffer, but it actually improved slightly, probably due to a smoother pedal stroke. My sprint absolutely improved…enough to grab a few podiums in local crits. 

Frank Stein wrote:

Listen to HAFE. He used to be a good rider. 

It hurts more when it’s true.