Broken Schlumpf Crank

I may feel like I have to post about every ride I do, but, honestly, I only post when something interesting happens. This morning I got some good karma. So, to make up for it, and to balance the world out, on the way home this evening, I got some bad karma.

Heading down Clerkenwell Road, I was approaching some traffic lights that were about to change, so I had to speed up a bit to get through. Just as I got to the other side I noticed my right foot felt a bit wobbly. If you’ve ever had a loose crank, bent pedal spindle or pedal bearing loss then you’ll know exactly the kind of feeling I mean.

So I stopped ASAP and took a look. I waggled the pedals but the felt ok. Wiggled the crank and there was a bit of movement. Was that it? Ah, no, it’s a Schlumpf, so there’s always a bit of play. Tried wiggling the crank in relation to the opposite one and it was solid. With the uni upside down I ‘rode’ it with my hands but couldn’t feel anything out of the ordinary. Maybe I’d just imagined it. I’ll jump on and carry on home.

Strait away I notice that something really wasn’t right at all. So I hopped off and took another look. This is what I saw;

Now, I don’t do trials. I don’t hop, and, apart from the odd kerb I drop down, the thing almost never leaves the floor. At 13 stone I’m not exactly a real heavy weight. So, I long ago resigned myself to never being able to tick the box on the unicycle quiz to say that I’d broken a crank. But there it is.

I know that when I’m in high gear it does feel like I’m pushing very hard on the cranks, and particularly when I change up it can be a push. But I really didn’t expect it to go like that.

So, all you non-splined Schlumpf owners out there, are there any particular brands of crank that you recommend? I’d guess ones with very low Q factor, but I’m just wondering what works well for you.

STM - gutted to be losing almost a week of RTL training :frowning:




I wonder if hard knocks from UPDs caused the initial crack rather than just regular hard pedaling. Then once the crack was started regular hard pedaling could have made it bigger till it became noticeable. The anodized coating could have covered up the crack (or manufacturing defect) during the initial stages so that it wouldn’t have been noticeable by casual visual inspection till it got to the point where the crack expanded and became very obviously noticeable.

You ought to see if Florian wants you to send in the crank so he can see if there was possibly some sort of manufacturing defect (a void in the metal or something).

Don’t worry…I am 100% confident in the Goonies finishing RTL as the #1 team!

…even with a week less of training.

It could have been there for a while I suppose. I’ll admit that I’ve never really inspected the cranks for things like that - but then again, I’ve never felt the need to. Although I’ve had several UPDs, I can’t remember any that would have been particulaly harsh on the pedals, although I’m normally paying more attention to how I land than what the unicycle is doint!

I’ll send Florian an email anyway as I expect he’ll be interested to at least see photos of it, and possibly post them if he wants.

Oh, and siafirede, don’t worry. I’m not going to miss the week of RTL training after all. I commuted in on my 24" Hookwormed Blizzard. It didn’t take as long as I expected, but it’s a whole new experience riding something that size for 5 miles in London. I think that has now become my 2nd favorite commuting uni!


Mine did exactly the same when I was in NZ. I think it may be a warranty thing, but you have to wait for the part to come.

I have a pair of 150s at mine, but I guess you’re in London at the mo. They are prowheel cranks, and seem to work okay.

I bunged an old pair of steel cranks on mine for a couple of days when I broke mine, does the blizzard not have square taper?


Yup, that does look like exactly the same thing!

Yeah, I’m in London, but also with a lack of tools. I’ve got a crank extractor, the special metal sleve required, and even some random cranks sitting back in Nottingham. But that’s 150 miles away :frowning:

The Blizzard has some 127 Qu-Ax cranks on, but they’ve got pretty high Q factor. So, combined with the lack of tools, it’s not really an option. But the Blizzard was fun this morning, so I’ll ride that for the rest of the week. I’m sure there must be some kind of multiplier that I’m allowed to use if training on a 24" wheel. Maybe I could count it as muni? :smiley:


I’ve had hairline cracks develop in cranks over a long time (most recently a pair of prowheel 150s on my muni) but never actually had one snap completely. Perhaps I’m just paranoid - I always inspect them and change them if any cracks start appearing because I had one snap on a bike once (mountain bike with cheap cranks that had been dropped a lot) and it took a big chunk out of my calf.

Glad you didn’t crash.


Your timing is fantastic! On the strength of Joes ‘Prowheel cranks work fine’ comment, I have just ordered a pair of 127 Prowheels! Being a bit shorter, they should be a bit stronger.

Well, I’d been considering the benefits of shorter cranks anyway, even though I liked the 150s I had. If I can get the broken ones swapped under warranty then at least I’ll have some 150s I can change back to, and something else to put in the spare parts bag for RTL :smiley:


I don’t think there’s anything wrong with prowheels - in fact I think they’re some of the better square taper cranks on offer in useful unicycle lengths. The ones that started to crack on my muni had been on there for a couple of years, done a lot of miles of pretty rocky riding and been dropped numerous times down rocky slopes. At £15 a pair I think two years is a reasonable lifespan on a muni. I had no worries about buying another pair to replace them.

The problem you might have on a road machine is they’re quite angled so you’ll end up with a big Q, which I actually like on the muni. Strength-wise I don’t think there’s a problem. They look quite nice as well.


New crank update

Well, at the weekend I changed the cranks over. Of all the unicycle related scary things I have ever done, I think that changing a Schlumpf crank is the worst. Tightening the crank extractor in to the adapter which then goes in to a finely crafted and delicate mechanism was bad enough, but the pressure I had to put on it to actually get the right crank off (the left wasn’t so bad) will give me nightmares for months to come!

Anyway after close inspection of the left hand crank, I noticed that there’s a crack appearing in that too in exactly the same place. Florian has confirmed that there was a dodgy batch of 152mm Schlumpf cranks about 2 years ago and is sending over some replacements. If you are riding with a set of these, I’d suggest you give them a careful inspection soon.

So, on went the 127 Pro-Wheels. They looked to have a bit more Q-factor than I’d have liked, but the shifting was very successful actually. Possibly more successful than with the old cranks on. Mind you, at the same time as swapping cranks, I also swapped to MG1 pedals and a new pair of trainers. It seems to be a combination that works.

On the flat, the shorter cranks certainly seem a bit faster as I can spin that much quicker. There were lots of opportunities on Saturday to test them out for hill climbing, and they were certainly harder to climb with, although not quite as hard as I’d expected.


One year old and here’s the pic.

I was climbing a moderate hill in 2nd gear, then I felt a wobble for a 1 second, then upd. Landed on my feet so I’m okay.

Since I had the Schlumpf, I put a few drops of oil in the hub and that’s it. I never touched the cranks bolts. But a funny thing; I just got a torque wrench for christmas.

Where should I get new cranks?

You can either get the same schlumpf cranks at

Or You can try out some ProWheel cranks.

You probably want to get a crank with some Q factor b/c if you are using a crank with no q, you increase the chance of an accidental shift.

lol thats broken… :stuck_out_tongue:

I like the prowheels. They’re pretty much the best square taper cranks I’ve ridden for pretty much anything. No GUni experience yet, though:(

They have reasonable standing room for flatland, lots of q-factor, and are light. I have every size of prowheel from 102mm to 165mm.

I didn’t think they made a 165mm crank. I thought the only sizes they made were 102, 127, 150, & 170mm.

I wouldn’t have thought 5 mm would make much difference. I switched my 150 cranks to 170’s on my Muni and love the control they offer (they also have more Q-factor) but it is hard to pedal smoothly. I rode a KH 24 w/ 165’s and it was just as smooth as my 150 mm cranks.

Actually, you’re right. I took a second look at my crank collection and I have the 102mm prowheel, the 127mm, and the 152, but the 165mm cranks turned out to be “MEL” or something. I haven’t ever used cranks that long so it doesn’t matter anyway though :roll_eyes:

The 152mms are the longest I have ever wanted.

Mine were the 152s. I’m thinking about 150/125 combo. My guess is that you don’t like them since you got that nice collection.

If you are talking about the dual drilled KH moment 125/150 cranks…they will not fit on your schlumpf hub. You have the square taper road schlumpf hub, not the KH/Schlumpf muni ISIS hub (by the look of the pic in your thread).

I also have 114mm qu-ax cranks, 89mm united cranks, 140mm MEL cranks, and some weird no-branders in my square taper set.

I’ve never really considered dual-hole cranks, if I travel somewhere on the shorter ones the shorter ones are fine for whatever terrain I encounter. I’ve ridden through a bog abound with tree roots and a full bmx track on 89mm cranks(yes, at times it felt a bit like coasting over bumps). I wouldn’t recommend it, but it was a good experience.

I only have one pair of ISIS cranks, so I have no variety for anything over a 2ft drop, which is fine for now.

Thanks for the help siafirede.

Emailed schumpf to see if I can recall the hub. And/or to order new cranks but no response yet.

here’s a vid of me … thinking that I’m doing it right.

Note: I didn’t start with the drill. I did have the drill on the lowest torque setting.