I have been riding my 36" for @ 6 months and have doing OK. Last weekend I rode the MS 150 mile ride on my uni and survived it but I need to get faster. I started trying to use the 125s and have gone completely stupid. I don’t know what I am doing wrong. Have any of you any suggestions. I don’t want to revert back to the 150s and can’t quite understand why such a small difference is creation such a big problem.
Frustrated Buck
Practice, practice. Going from 150 to 125 is a fairly large jump, even if it doesn’t sound like it. Your legs and your brain must get used to the change.
Since you survived 150 miles I’m going to assume you’re not a super-noob, but you have to keep in mind that you need to change your technique a bit with shorter cranks. I find with the 125s (vs. 150s) on my KH36 I have to keep my momentum up a lot more because I can’t just torque myself out of tricky situations as easily. Settling into your new crank length will get easier as you build your legs up and otherwise get used to the change. 125s use a completely different set of muscles in your legs and, as I say, make your uni into a different animal. Unfortunately, the only thing that’ll get you where you want to be is time in the saddle.
Don’t give up hope, comrade! Good luck.
P.S. Someone will probably want to tell you that this thread should’ve gone in Rec.Sport.Unicycling, but most of us don’t care that much.
My $.02:
Try 140’s for a while, I only liked 125’s on the flats and don’t ride enough to get any more comfortable on 125’s.
Post your next unicycle thread in RSU. Don’t listen to those who say it’s OK to post unicycle threads in JC.
Even after a year of riding on 125s, I still have problems mounting. It may never get easier… but the shorter cranks make a huge difference in saddle comfort & speed.
If your ride is largely flat, and you get to a point where you’re comfortable on 125s, you might consider even shorter cranks. I rode most of the 500km Uninam tour on 110mm cranks, including several mountain passes, with little difficulty after the initial period of adjustment. Having trained on 125mm cranks, the switch to 110 wasn’t as big a jump as the 150mm - 125mm change.
Don’t give up! Riding a unicycle is difficult no matter how you slice it… putting small cranks on a big wheel is only going to make things harder, but it’ll pay off in the long run. Until you’re comfortable, just be sure to wear a little extra protective gear 
crank choices
Have you considered using the double holed moment cranks? I think they make 150 to 125s. A friend of mine and I just rode a 50 mile ride. He rode with double hole cranks and carried a pedal wrench with just in case he needed 150s. He did really well and he didn’t gear down during the ride, but I’m sure having the option was good for him.
Ben
My biggest issue with 125’s is shifting the seat up. it’s about a 1" difference in pedal height, and I find it really uncomfortable if I don’t shift the seat up when I shift the pedals on the KH Moments.
Also, mounting-wise: I have to consciously bear down harder with my non-dominant (i.e. forward) foot to get things rolling. After that, it’s all about keeping a smooth cadence with steady momentum.
The 125’s definitely hammer my leg muscles more, but it is a noticeably smoother and faster ride. Well worth your time to “learn the new length”, IMO.
Lighter cranks and pedals help quite a bit
I have the old Radial 36 steel wheel set up. Being kinda heavy you would think it would be sorta insensitive to crank-pedal weight.
I was surprised when I switched from steel cranks with heavy snafus (with protectors) , to Sugino cranks and 330 gr/ pr Dimension’s.
It made a huge difference. I have been running these pedals for about 2 years with no trouble. At 10 $/ pr , I can’t recommend them enough as an uber light pedal with excellent grip. It is made from a high quality sharp nylon that works in mud and rain just fine. It is slightly lame in that it lacks the angle ramps like the Odessy twisted pc pedals that are maybe the best 14 $ off road pedal, but those are 80 grams heavier. In practice, riding on the streets being not tricky, the box pedal shape has been no problem.
You didn’t write what you are pedaling on now, but if you want to try a 330 gr pedal set for a 36 these are very good. The improvement was instant and I won’t go back to heavy pedals on a 36.
http://aebike.com/page.cfm?PageID=30&action=details&sku=PD1097
The Sugeno cranks are lighter than steel and look really good, but I don’t know where to buy short ones now.
I’m still a noob, barely able to cover a few miles while encountering a dozen or more UPDs, but the only setup I can ride so far is 125mm on my KH29. Tried 150 originally, and couldn’t make any progress on any terrain, so I tried 125 settings and it clicked, but my legs get tired going uphill and I can barely manage anything unpaved. I’m thinking of practicing for awhile in the 150mm holes to see if I can conquer more varied surfaces without excessive speed loss. Generally, I hope to stick to paved bike paths and light muni, but the 29’er and 125mm holes is all i can ride at this point. My son’s 20" Torker even kicks my ass at every attempt.
I do, and I responded in RSU. 
i rode my 26 from the city to the beach and back with suede (suedestar) he rode his kh36 with 125 150 double holes i was on my nimbus 26 with hightop seat and 125 moments hookworm tyre he was nightrider tyre kh frame nimbus stealth rim freeride rail seat i had a go on it i started off on 150s but they were an inch to long so i couldnt ride properly i set to 125s and i fiound it alot easier to mount and ride i was riding downstairs on his 36 he didnt mind too much all up the 36 is a great uni for cruising compared to a 26 even though i was keeping up on my 26 with 125s and him on 36 with 150s it was hard.
Punctuation and capitalization rules were implemented for a reason.
If you want anyone to know what you’re saying: obey them.
The only way to get used to new cranks is to put some time in the saddle. I have been riding Quax square taper 125s on my Nimbus 36er for a year now. I think they are a great balance between torque and speed.
A couple days ago my neighbor was planning on throwing away a monkey bike with 90mm cranks on it, I salvaged the cranks and slapped em on my 36er. After that I had the same problem as you. When I was riding with them at first I would lose it if I lost focus for a moment, and going at any reasonable speed scared me good.
Though after a few rides to and from work I’m used to them and they are amazing. I wouldn’t reccomend them for anything other than flattish roads, but still they’re crazy. I have had some of my fastest rides with these. Just today I averaged almost 16mph coming home from work! I can get the freemont more than 90% of the time now as well. It just takes some time to get used to shorter cranks. Keep trying.
150 vs 125 cranks and road shoulder problems
Thanks for all the good advise and I am planing on implementing it.I ordered some 140s to see if I can sneak up on it. Also, I started doing more leg strengthening exercises in the form of leg presses, cutting the grass with a weight vest on and hopping my 26 inch uni which, is the most fun. I have another problem ( well probably several) but this has to do with the unicycle and the slop of the shoulder on the road. If the side of the road is sloped it messes with me big time. I am riding the Nimbus Night Rider tire with 65 psi. I tried both increasing and decreasing the psi but not much difference. I do my best to stay there but sometimes I need to pop out to stay on, any suggestions