For a Schlumpf: straight or flared-out cranks?

I’ve owned my Schlumpf 29" since late 2005, but always found it somewhat difficult to ride, let alone switch on the fly. Recently though, I’ve taken to riding it more, and it now starts to “click” (not the unicycle, but mentally). Both in terms of speed, and in feasibility of switching gears while riding. I currently have 150 mm cranks on it but it definitely feels like I should go shorter.

Now my question: Do you recommend cranks which flare out (some call it Q-factor), like the original Schlumpf cranks, or cranks that are straight?

One advantage of flared-out cranks is that you won’t so easily switch gears by accident, but on the other hand, less Q-factor is better for spinning fast. Also, flared-out cranks make switching gears on purpose a little bit more difficult because your heel has to go farther inward to kick the button. I have pinned pedals which is much better for control, but the pins prevent my foot from making a large sideways motion for switching. So what I do as a preparation for switching is reposition my foot so that it is closer to the button, then switch, then position my foot back.

If you’ve got the 2nd generation schlumpf frame then some cranks won’t fit on it, as they rub on the big bearing holders. I found qu-ax cranks wouldn’t fit.


Well, the frame is from end 2005 so I guess it’s first generation? I don’t know what the difference is with 2nd generation. There are pictures of my frame in First Schlumpf GUni test ride , towards the bottom. Some parts have changed but the frame is still the same. Is it second generation? Would first generation frames have no issue with the Qu-ax cranks? Anyway, thanks Joe for the warning.

If anyone has advice as to straight or flared cranks, I’d like to hear.

What I meant by first generation = looks like a normal unicycle frame
2nd = looks like a bike fork on acid.

Yours is 2nd.

I had problems with qu-ax 125 cranks rubbing on the bearing holder. I though Tony Melton runs them on his, so I think there may be some tolerance issue, or the design of the cranks may have changed.

I really like 125mm, I just use Schlumpf cranks at the moment, cos it is least hassle. It’s quite a narrow hub anyway.

Much easier to shift on 125mm.


That’s probably 127 mm? Schlumpf doesn’t sell 125. (Not that it would make a big difference.)

And I agree that the hub is quite narrow. But my point was not so much in total Q-factor, but in the foot being “far” away from the shift button.

Any idea why that is? Is foot position with respect to the button better? Or maybe because the absolute velocity change for the pedal (going from one gear to the other or v.v.) is smaller? I found that with 152 mm cranks, shifting was somewhat more difficult than with 170 mm, and I attribute that to less control. Something to get used to, admittedly.

Nevertheless, 127 sounds rather short to me. It would be equivalent to about 82 mm non-geared.

Shifting for me is dramatically easier with 127mm Torker LX cranks than the Schlumpf 152 cranks (which I only replaced because one snapped in half leaving me on the pavement).

This is on a 36er. I think the length is perfectly practical on a 29er. I did have one accidental shift with some bulky shoes.

I had Schlumpf 152mm cranks on mine until they cracked. I was thinking about moving down a size anyway, and that was the incentive. I went for 127mm Pro Wheel (Qu-Ax) ones, and was amazed with the ease that I got used to them. The shifting seemed to be much more natural, but without ever having an accidental shift. (I only had 1 on the longer cranks, and that was whilst holding on to a railing at a red light).

I had the same Schlumpf frame as you when I swapped for these cranks, and had no problem at all, but this is the same combination that Joe tried and had the problem with the crank and frame rubbing. It might just be an issue with tolerance, but for the cost of a few Euros, is probably worth trying.


I would get the 127 Schlumpf cranks. They are lightweight and the Q factor is good. I am afraid of using flat cranks on a schlumpf because of the increased possibility of accidental shifting. Shifting will initially be easier on the 127s because you can hit the button with a different part of your foot (ankle/inner foot), but after trying out shifting with 150s I found shifting to be easy on those too. I have size 11.5 US feet, so maybe that is why shifting with 150s is easy as well, but overall shifting has never been a problem for me.

The smaller cranks will make the guni ride a little bit more squirrely at first and you will need to get used to controlling it, but after a few long rides you will love the smaller cranks.

When succesfully attacking the hour-worldrecord, Greame O’bree used gearings of a washmachine to get his pedals as near to each other as possible.

I think naturally your feet tend to ‘go small’ at higher rpm’s, kind of the same like the difference between walking and running. So same as in bicycling I certainly would prefer straight crancks if it was for myself.

I don’t have a Guni, but have been riding Gilby’s long ago.
Especially with the grip that pinned pedals provide provide, you should have the dicipline to not accidently shift. If you ride it a lot, then I’m sure you’ll just get used to how-to place your feet (to still ride with comfort AND not shift).

Only in case you have a spine in such an extreme shape that your feet are always and ever tend to be in clown-position (as in the opposit of I-need-to-pee-position), then I would choose crancks with Q factor.

No ones arguing that lower-Q is faster and more efficient. But with straight cranks, my ankle is just a couple of mm’s away from the shifter button. That terrifies me.

I rode straight 125mm cranks (Qu-Ax) at RTL, and didn’t have any unintended shifts or neutrals on the road. I had an unintended shift on a mount where my foot didn’t get on the pedal properly and hit the button as it came around. I don’t think accidentally hitting the button at speed is a big issue.