Those 150s on Petes Schulmpf eventually broke. I took the opportunity to change them for 125s, and contrary to the gist of this thread, I found them a great improvement. I know I was generally getting fitter at the time, but I found them just as easy for hills as the 150s were.
STM
Yeah it’s just as easy to walk the unicycle up the hill no matter what cranks you have!
Joe
The rotating mass is much greater on a 36er, even only considering the tire, than a 29er. I have no difficulties with any crank length on the 29er.
I’ve KH29ed many miles, both off and on-road, with 165s (funny how long that seems now), many miles with 150s, a few miles with 137s (love this length), and many miles with 125s. The wheel is light, easy to spin, and the 29" uni is easy (for me) to mount no matter what cranks I’m using. The shorter cranks seem to work fine for on or off-road.
Long uphills may be an exception. On long climbs I’ve done (Whiteface: 3500 ft climb over 8 miles; Equinox: 3200 ft climb over 5.4 miles), the 165s give me a big lever to spin the wheel, makes it feel easy to pedal, even when I’m totally hammered. I know Tom from the SF bay area (Tholub) has done Diablo (similar to Whiteface) on a 29er/125s and was happy with his setup. I’m probably going to try shorter cranks on Whiteface this year.
To sum up…on the ungeared 29er, I like the 125s best on-road (never tried shorter), the 137s for trails. Maybe 150s for big climbs.
But, at the suggestion of Rolandisimo, on my KH29/Schlumpf I set the pedals in the 150 position, for added power in, as Harper said, small disruptions. Also, in 1:1.5, the possible seat discomfort of long cranks is mitigated by slower revs.
Spencer - was this on a 29er?
Related to this discussion, I used my new GPS watch to quantify the effects of crank size and gearing on speed as reported in this new thread.
How true! 
I ride 150’s on my coker as well.. And it’s ideal for all the hills in town, and great in the trails. There also decent for some trials on the big wheel.
chicken.
Dang…looks like a great ride and of course I’m always up for events that have me puking by the end, but unfortunately this is the same weekend as the annual MS ride I do in Seattle. Gotta do my part there.
I want a century this year. I’m thinking about the Seattle to Portland ride in mid-July, but it’s back-to-back centuries, and I only [I]really[I] need one. Plus my June is cranked at work, might be hard to get ready.
What about a self-planned, self-supported Upstate NY century in late September? You’ll be in such good shape from the NYC ride that knocking off a second cent in the month should be totally doable. Around Cayuga Lake perhaps?
I love my 114’s even for climbing I did a 32 mile ride up and down two of the steepest climbs in Portland Rocky Butte(612’ with a 5.4% grade) and Mt.Tabor(643 ft with a .15% to 8.4% grade) and had no problems and was clocked by a fellow cyclist who trusts his computer with his life at 28mph for the majority of the downhill of Rocky Butte. YAY SHORT CRANKS! haha
Wow, Tim Morin! Howzeet goin’ mon?
Yes. It was Petes (Mr Boogiejuice’s mate), but since I’ve had it I have changed the cranks, pedals, frame, seatpost, seat, tyre and brake. But it’s still got the same 29" rim 
Oh, and Joe… 
STM
Oh well. Yes, of course let us know when you’ll be here and we’ll get something together!
Ducktape that is some impressive speed, but as I care for my limbs, I’m sticking with 125s for now.
I care for my limbs too haha with a proper spin technique it’s not even that hard to get those speeds comfortably. I didn’t know until the cyclist told me that I was spinning any faster than 19mph that’s how smooth it felt.
My theory on that is that shorter cranks force you to push harder on the pedals which lifts you slightly from the saddle. So you support more of your weight with your legs and less on the saddle.
But that theory doesn’t make as much sense for flat riding cause when riding flat terrain it feels like I have just as much weight on the saddle with shorter cranks as with longer cranks.
Mine own theory has the “saddle savings” on short cranks down to roughly equal parts “less leg movement in the strict sense”, and “less bouncy-bouncy (smoother pedal stroke)” with the short cranks vs. long. Between less wobble and less bounce, you cut out two big sources of irritation on the long-term sit and spin sections, in my experience.
billnye
John M
KH 36, I decided to try to give my 114mm cranks a decent trial over the 125’s.
After a few rides, of a couple of 45k, 50 and 55k, my average performance from my GPS log is not better than with 125 cranks overall. It is surprising that 11mm can make such a difference in feel of the uni though.
The control was managed with the 114, but definitely with more pitching than I would do on 125’s, even after about 200k of riding. I needed to be more attentive, for sure on rough or cracked pavement surfaces, or loose gravel, washboard, etc. Since riding into wind seems like more work, the average dropped down to about 17kph, but downwind I was averaging about 23kph.
I think that today was my last ride with the 114’s. I UPD’d shoulder-checking as I approached the merging lane off the overpass, (left some skin on the roadway!) and that momentary lack of concentration probably wouldn’t have caused the same effect on 125’s, imo. I think that probably, for me, the 125’s are a safer choice.
I urge you to keep trying the 114s. I have found them SO SO Much nicer and smoother than 125s. When you’re doing a ride without any steep climbing, slap them on. 200km is not enough of a trial. After 500 to 750km you will be loving those babies.
After 1600km of riding recently on a geared 36, mostly in high gear which is the same leverage as using 100mm on a regular 36, I did a couple of rides last week on 125s ungeared. Man it felt bad. I was dying for shorter cranks. 100mm is the way to go once you’re used to it. But 110/114 is an ideal compromise. You actually can climb ok on them with practice. The first time I realized that was on the Alps Tour in Austria in 2005. Ken Looi climbed our first pass with 110s easily and said the descent down the other side was one of the best he’d done. It was 800m in the rain, kind of steep, and he just let it fly. That isn’t for everyone, but the idea holds: once you’re used to 110s they are fantastic. YMMV of course:)
—Nathan
I started with 125mm on my Coker because I haven’t received my 114mm yet, then I changed for the 114mm it was much smoother. I tried the 125mm again and it’s just too long for a Coker:p I tried my friend Coker with 165mm and It’s just really too long. I tried it with 137mm too, it was okay, but I still like my 114mm alot more. I did 34.5 km/h with the 137mm and 34.0 with my 114mm, I dont know if it’s my friends speedometre or something, but the shorter cranks doesn’t go really faster. Exept that with my 114mm cranks, I’m riding at 25km/h all the time, and it’s a comfy speed for me.
125s are a safer choice, and are a little more versatile.
114s feel slightly nicer to me on a long ride though.
I haven’t rode an ungeared 36er on the road in a long time though.