Schlumpf Uni- yet another review

I finally got my Schlumpf 29’er set up today. I’ve been so busy that it’s only had a cursory ride up and down the road as it was waiting for me to set up a proper seat. I gave up on the bike seat idea because I couldn’t find a stem long enough to not bang my legs on.

So after an afternoon of chopping up my new Scott Wallis/Carbon seat (thanks Scott!) I finally have it rideable. I went with the theory that long distance seats should be flat as possible so that you aren’t squishing your squishy bits for hours on end. It’s still not perfect, but I carved up the foam so that the saddle has only a minimal curvature. I switched over to my Miyata carbon base due to the lesser concavity of it.

The set-up is as follows:
Schlumpf 29’er- hub, 125mm cranks, frame as standard
Big Apple tyre
Snafu pedals
Miyata carbon seatbase
Scott Wallis Deathgrip handle
Scotts wire/leather seatcover
Scotts double density foam, chopped to bits to make it flat

So yes, it was all set to go- only problem was that I was down with a bad flu-thought my head was going to implode (someone was tightening a vice around it:( ).

But then I thought, I’d feel much worse if I had to wait until I was feeling better before riding it, so off I went.

The ride: 17km to Makara Beach from my house- lot’s of rolling hills, but slightly more down than up.

It took a few practice attempts earlier in the week before I could actually freemount the thing. It rides like a 43.5" wheel- so there is a lot of momentum built in. However, it is also much lighter than a Coker- so even though it was geared up more, it felt very similar in responsiveness to the Coker.

Off I went up the first hill- this thing rockets along like my Diet Coker on speed. My legs weren’t feeling great, so I waddled my way up that hill and ended up flicking it over th 1:1 mode. After riding in 1:1.5 mode I was unable to ride freemount it in 1:1- it took three attempts and three UPDs before I could get going again.

Back down the hill and I flicked it to 1:1.5 and this thing just rocketed away. It is slightly twitcher than a Coker, so more attention is needed to keep this thing from killing you. I had one high speed UPD, with resulting in the sound of my shiny new Carbon Deathgrip handle rubbing it’s way across the tarmac at 25km/h. Scratched but still intact, I was a bit more cautious for the rest of the ride, along with the fact that I was about to throw up all over the road.

I made it to Makara Beach in 40:07. My best Coker (110mm cranks) Time is 40:20. The Coker time was set when I was fit and not dying of the flu, so I think on a better day the Schlumpf should be at least 5min faster. The return trip took 1:29:18. My best Coker time (and it took some effort to do) is 1:30:20.

I rode with a Road Cyclist on the way back, and for the first time I felt like I could keep up a reasonable pace without spinning my legs off. The Schlumpf feels more like you’re riding a bike than a unicycle- it goes that fast. One other thing- the flattened seat is way more comfy than my previous curved seats. It required your hands firmly on the handle to stop you slipping forwards, but distance riders tend to keep their hands on the handle all the time anyway.

The only trouble I had with the Schlumpf was the wheelbuild- the spokes aren’t tensioned that well and were clicking all the time. Looks like my first upgrade will be a decent wheelbuild.

Next challenge will be the Basin Reserve (where I set the 24hr record). Will see how fast it goes under more measured conditions when I’m feeling better.


Thanks for a great assessment of the guni, Ken. Certainly I trust your opinion of Schlumpf’s uni for several reasons (you’ve met him and toured the shop, and you’re one of the world’s best riders for long-distance and for speed, as my brother learned on your ride. It’s amazing what you did with yours already, given that it was your first ride AND you were ill. I can’t wait to read your updates.

Speaking of updates, is yours the updated hub? I just got a note from Florian that he’s sending out new, improved hubs in a month or so. The improvement is that the shifting will be smoother. My only bad UPD came when I shifted but the uni freewheeled, and I fell on my back. I also had a mild uphill UPD where I rode over a long stick sideways and slipped, resulting only in a tiny scrape (thanks to my wristguards!).

Note that according to people who have actually measured this, the rollout is more like 46" than 43". That’s due to the fat tire. Also, it’s actually 1.55:1, not 1.50:1, which is only a small (3%) difference but bears mention.

Oh – last thing. I’m not riding mine for a few weeks. Yesterday I noticed that one of the crank arms was super loose. Apparently this hasn’t happened before, so Florian was surprised to hear that it almost fell off. I’m not a good mechanic, so I’m waiting till my club meets again so that Dave Bagley, the other East American owner of a guni, can fix it with me. So far I’ve put 600 miles on it in only a few months (including a 90-mile ride one day), but I’ve never ridden it off big curbs or tried hopping on it, so I’m wondering how this happened.

Ride on!


So Ken, was it easy to click and shift on the fly? Also, for comparison’s sake, how many years have you been unicycling?

David, how do you feel about the difficulty of the on-the-fly shift? How many years have you ridden?

Loaning geared unicycles to people who have never ridden them puts them in a position where they are subject to repeated mount failures. Often the unicycle goes bouncing down the pavement (on the pedals and saddle, the parts that stick out) at high speeds. Think about what this is doing to your cranks. I have seen this many times in the past, especially with the aluminum cranks that I insisted people use on the first soft axles that I made. I saw several people bouncing your GUni off the pavement at Grant’s Tomb last week.

I disagree with Ken’s assessment that inertia is built into the gearing scheme by nature. The rotational or angular inertia is determined entirely by the mass and radius of the wheel (actually, the heavier tire). It is really quite a bit smaller on the 29er’s than the Coker because of the massive Coker tire. The Big Apple is quite a fat boy and does have substantially more angular inertia than a 24 inch tire and I believe that makes it easier to ride in geared mode. Others disagree with my opinion, most notably Steve Howard who changed from the 29 inch Big Apple to a 26 inch wheel and had better success with geared unicycle riding.

On another note I find it incredible that Ken could improve on his best Coker times riding a geared unicycle on his maiden voyage while ill. Riding a geared unicycle on flat, smooth terrain is definitely faster than a Coker. On irregular terrain this is a different story. This is undoubtedly a tribute to his outstanding riding skills.

I managed to shift on the fly the first time I tried, going from low to high. Initially I found it easier to downshift, which I got on the first or second try, but lately I’ve found it easier to upshift. However, I’ve also gotten really good at riding up steep hills in my area, negating the need for the low gear most of the time. I find that when going uphill in high gear I can usual match or top my low-gear speeds on the same incline. Then there is the UPD issue: I had a bad UPD while shifting and have had some problems with the hub since (pins slipping), so I generally kept it in high gear the last few weeks. Recently I practiced switching gears again, and I found it easier to switch low-to-high.

I should mention again that mine is the 29" guni. It’s much easier to switch on a smaller wheel. With practice, swtiching on the fly is pretty simple and quite nice for when you need to slow things down.

This is my 26th year of riding (with only a few months total of non-riding in all that time), and I’m level 7, and I’ve ridden a Coker for 4+ years (and over 4,000 miles). I think all of those factors contributed to my success in making the transition to the guni.

By the way, I rode my Coker for the first time in over two months, and it felt really EASY! I can’t wait to see how fast I can make it home today after work.

Yeah, that could definitely have contributed to the temporary demise of my guni. I will have to rethink the loan procedure for my club. I want everyone to try out the guni, but not if it means I can’t ride it because it’s out of commission.

I want to try out one of these beasts so bad!

Have you got any photos of your Schlumpf with the improved carbon/deathgrip flat saddle, Ken? Your saddle cover which came with our DG handles is a Gemcrest low profile leather cover.

I rode Ken’s Schlumpf briefly in the weekend. It was dark and the seat was very low and was also a bike seat rather than a uni seat, so it was a brief impression of the Schlumpf’s ride characteristics only. In 1:1.55 gear mode it sure was fast, but didn’t handle so well at low speeds which is kinda to be expected. I didn’t feel very comfortable on it but thats most likely because of the low saddle and having to hold the bar-end arrangement under the saddle the whole time. I’d really like to try it again with a uni saddle at correct seat height.

I noticed that the seat tube of Ken’s frame is 25.4mm diameter at the top, then changes to somewhat less than 25.4mm just below the level of the top drink bottle boss. Its impossible to get a 25.4mm seatpost past the level of the drink bottle boss. What Ken had done was to file off his seatpost so that it fit. Is anyone else’s schlumpf seat tube like this? I can’t think why a change in seat tube diameter would be intentionally designed into the frame, unless it were to force you to use a short seatpost…

David, I think the best strategy for you here is to “teach your club a lesson” by loaning your guni to the Seattle Area Riders for the next several months. With the exception of Bruce who breaks spokes, we’ve already established a sound track record of successful guni borrowing with Blueshift, the original 29" guni which formerly belonged to Harper and is now property of the club. This would be just the thing to help us get through the rainy season here in Seattle, and in return we’ll dry it off after every ride, plus have Harper bully the mayor into naming New York a “Sister City” to Seattle.

Oh yeah, plus visitation rights obviously, as long as you give us a week or two notice.

Thanks in advance,


Thanks everyone. I’ll go take a photo of it now and have it posted. It’s BEeautiful!

David- it’s the orignal hub, I don’t know why Florian is going through the expense of sending out new hub parts. Apparently cos it locked up once, when he was putting a lot of pressure on the hub without feeling the play (which you need to or it could lock up). Anyway, just goes to show what a perfectionist he is. And the fact that he’d sent back 2 batches of frames to Taiwan because they didnt’ meet his specifications. I feel a lot safer knowing that Florians workmanship is inside everyone of those hubs.
Thanks for measuring the rollout- I assumed it was 1:1.5 x 29" tyre. It’s good to know that it is so much higher than a Coker- I wouldn’t want 2 unicycles with such similar rollouts. It might explain why I was pedalling so slowly and still going faster than my Coker. If I can pick up the courage to really rev it up like my Coker it should be a pretty amazing machine.

Steveyo- I haven’t tried shifting on the fly yet- let me get some distance on it first. I’ve been riding since December 2000, less about 6months off with a broken ankle.

Thanks for your assessment Harper- Physics was my worst subject at Uni. I think you’re right in that most of the resistance I’m feeling is from the higher gear rather than the inertia of the wheel- it is lighter and closer to the axle after all. That could explain some of the twitchiness compared to the Coker.

Tony- for some reason the 25.2 seatpost that Florian supplied slips into the seat tube just fine, whereas the 25.2 alloy bicycle seatpost I tried would only go in about half way and then get stuck. I had to ream the lower part of the seatpost to get it all the way in. I suspect that the seattube is slighly kinked from welding the 2 drink bottle bosses in there, although I can’t explain why Florians seatpost went in so easily.

I’m feeling a bit better today- might take it for another spin.


David: caution here. Tom tends to sell the unicycles of others. We all now own several of each others unicycles and Tom somehow has amassed a tidy fortune.

Ok, here’s a pic of the Schlumpf. Note that the seat still has a slight curve on it, but it’s actually less than in the photo because the front tends to bunch up a bit.

I went down to the Basin Reserve today to do some measured riding. Still wasn’t feeling great so only did 5 laps.

Schlumpf 29’er/125mm cranks
Course length: 465.22m
5 laps: 5min28secs
Average speed: 25.5km/h

Tubeless Coker 102mm cranks (time from early this year)
10 laps: 10min53
Average speed: 25.6km/h

Ok, so it was technically slower than my Coker time from early this year, but I think what held me back was that I was still not entirely confident on the Schlumpf yet (my second proper ride)- at that speed, even minor surface irregularities seem to throw you off a fair bit, whereas a Coker will plow straight over a pothole without second thoughts. There is definitely more thinking involved with riding a Schlumpf. I also do not trust the Big Apple tyre when going around corners- it feels very squirelly. (Anyone know of a good square profile road tyre?) I expect that on a smooth course with 100mm cranks the Schlumpf will leave the Coker for dead.

On another note- I had some difficulty riding the Schlumpf up the hill back home. It’s defintely geared higher than a Coker- even though it’s lighter and I use longer cranks than on my Coker. After flicking it back to 1:1- it felt woefully slow. My legs just wouldn’t spin fast after pushing such a large gear. It took foreever to rev it up to speed. I’m almost wishing the gears are spaced closer- ie 46" and 36" rollouts.

The question now is, should I use longer cranks still- ie 150mm, and be able to ride up and down everything, or go shorter 110mm and flick between gears. Option 1 is more efficient in that it’s possible to maintain your rhythm, and really let’s you power up hills, but if you can flick mentally between the 2 modes (and pedal fast regardless), then option 2 might work better.

Interesting saddle design. I’ve been playing with some similar ideas with making a flatter all foam seat for the Coker. I’m just not thinking I’ll end up going as flat as you are.

Attached are two pictures of its current state. The second picture shows the wedge that was cut out from the nose of the saddle. It’s on a CF Miyata style base which is a little bit flatter than the KH style base. Foam is from a 2005 KH Fusion. Seat cover is from a KH Fusion.

I’m thinking of adding some extra foam in the middle area of the seat to raise up the middle and flatten it out a bit more. I’ll have to ride it some more and see what I think will work.



Cool- what do you think of your flatter seats John?

I’ve only done 2 rides on my flattened seat and so far it seems more comfortable. Certainly I don’t get the feeling of getting my bits squished like I do with the KH seats. On long distance rides it is not necessary to use your crotch to do the steering, so there is no reason for a seat to be curved upwards.

I think I cut the foam similar to how you did it. Basically sliced off a wedge from the nose of the faom, and another wedge on the back of the foam, leaving the thickest mid-section of the foam to sit over the curve of the seatbase.

It’s the reason it took so long to get my Schlumpf set up- I tried a bike seat- which is really comfy, but couldn’t seem to get a stem long enough to get the handle out of my way- my knees kept banging it.

With flat seats you really need a good handle- basically the unicycle is set up more like a bike- the handle stops you sliding off the front of the seat. The advantage is that you are also distributing your weight like a biker- on your arms as well as your bottom. Most people do that to some extent anyway, but it’s easier to bend down or use a longer handle (lower posture and better weight distribution) when the seat isn’t curved upwards.

Professional (bi)cyclists spend hours in the saddle- I think unicyclists have a lot to learn from them in terms of seat set-up and weight distribution. Have not seen any bikes with seats curved upwards yet.

So far so good. I’ve only gone on one short ride with it. It’s wider in the middle than my air seat that I was using before so it’s going to take some adjustment on my part to get used to it.

I have the same problem with the bits getting squished which is the main reason I cut the wedge out of the front. I also think a flatter seat will allow more adjustment room to change the pressure points by moving around to different parts of the saddle.

I cut a similar wedge out of the front of my muni air saddle for the same reasons. It’s a good way to make a saddle more comfortable.

One thing I noticed with the cut down KH Fusion foam is that cutting the skin off the foam made the foam just a little bit more squishy. The skin adds a little bit of resistance to the squish. That works well when cutting the wedge out of the front, but I don’t want to mess things up by cutting the skin off any part of the back of the saddle. Instead I may stuff a little bit of extra foam under the middle part of the saddle to raise up the middle area to flatten it out.

I think the objective of a seat is to support your ischial tuberosities (the bony bits on your bum), without putting pressure on anything else. It shouldn’t do anything more. That’s why bike seats are:

  1. Flat
  2. Wider at the sides where it contacts your ischial tuberosities
  3. low profile (so they don’t squash other parts of your anatomy and allow freedom of movement.

The thinking behind unicycle seats is that:
a) It should be curved so that you don’t fall off the front. Also allows your crotch to do some of the steering
b) Softer is more comfortable
c) It should be a big fat brick shape to give you more control

I think (a) is only useful if you are doing freestyle because it let’s gives you more control and leaves your hands free to do other stuff. Fine when you’re riding for 5 minutes at at time. In distance and Muni, riders tend to keep the hands on the handle all the time, not only for handling but also to support some of the weight of the rider.
I think (b) is a total myth. If a seat supports you in the right places, it does not need to be soft. The reason soft seats are comfy is because it is nicer to squish the soft parts of your anatomy against something soft. If designed properly, the soft parts of your anatomy should not be squished against anything in the first place.
c) I think the thicker seats may give a bit more thigh control for turning, but I think they are overdone. A standard KH seat is probably twice as thick as it should be. It just makes it harder for short people with short seatposts and makes it heavier also. In the horizontal dimension (ie width), I think they can be slimmer too (not as slim as a bike seat), but enough that you have to have very muscly thighs to rub on them.

Maybe this calls for a new thread, we’re going way off topic.

Back to more experimenting :slight_smile:

This air seat from Scott Wallis looks pretty cool. It appears to provide a place for the sensitive parts.


Ken, I forgot to agree with your assessment of the spokes. When my guni arrived, the spokes were a mess. Unforch, I rode it like that for 200 miles. Forch, there were no problems (like broke spokes).

As to the seat topic: I rode 90 miles over 12 hours last month on my guni with the KH seat. It was the first time I’d ridden over 40 miles in a day without it hurting to pee afterwards, so I’m sold on the KH seat. It certainly does have limitations, as you note. Considering what doctors know about cyclists, saddles, and impotence, I’d say that it’s the best seat I’ve used, if only I use that one criterion. As it happens, for most of us, this is a really really really important criterion.

One other thing: You asked about crank length. I’ve left my cranks the way that I ordered them, which was 125 (I think – or 140s?). I find that they give me enough power for the uphills and enough control for the downhill, tho it did take me some time to get used to them. At this point (as I’ve already noted), I rarely shift on the fly – I just leave it permanently in high gear. I would definitely not want 110s – too dangerous for any turns and stops (for me, anyway).

I did change the pedals. I use super-grippy magnesium pedals with pins. They’re pretty light, and they are so grippy that it’s a bit tricky to shift (but still possible).

I found the Big Apple to be squirrelly at low pressures. Running the highest possible pressure seems to improve the ride on pavement. At low pressures the tire profile seems to deform too much around the rim while cornering. A higher pressure stiffens this cross section and it doesn’t feel as if the tire is rolling off the rim. It is similar to running a Gazz at too low pressure. On dirt it feels OK but on pavement it is practically unrideable (for sissies like me.)