The Nimbus 32" frame is 125mm – a 29" wheel wouldn’t look silly in that I don’t think, also the Hatchet frame is 125mm and it can take a 29" wheel too (the UDC website says up to 29" x 3") – a geared 29" Hatchet sounds pretty neat
Edit – I forgot that they sell a prebuilt 29" Hatchet now too.
What are the advantages of a 125mm hub over the 100mm? I’ve never had the opportunity to compare the two options side-by-side, but I would have thought that narrower q-factors would generally result in a smoother ride, since pedaling force can be applied closer to the center of gravity.
As far as I understand it, having flanges closer to each other results in more stress in the hub, resulting in a more important risk of spoke or flange breakage.
Basically, if you push on the side of the wheel (let’s say with 100 N), it will move a very little bit and put stress on the spokes, which will maintain it in place. But the constraints are vectors, so to resist 100 N from the side, you need 100*(SL/SLx).
SL : Spoke Length
SLx : Spoke length along the x axis
So if you get narrower flanges, the constraints increases greatly. You can see a visual demonstration on the following pics :
I appreciate that analysis. I looked up the hub geometries on the unicycle.com spoke length calculator, and (in this model) the difference is more extreme than I expected. The 25 mm difference is split equally between both the disc side of the hub and the non-disc side, but there’s significantly less space on the disc side to begin with, leaving the 100mm variant with just 17.2mm of offset. This means the 100 hub has nearly a 2x greater force concentration on those spokes if the model is representative.
hub & side
SLx
SL
Force concentration
100 mm disc side
17.2
335
19.5
100 mm non-disc
38.4
337
8.77
125 mm disc side
29.5
336
11.4
125 mm non-disc
51.0
338
6.63
All that said, it takes a tremendous amount of stress to brake a spoke. It’s never been an issue for me, but I’m sure I’ve got less experience than most other riders on this forum. Have you guys broken a lot of spokes?
I have broken several spokes on my G29, but I think they were not tight enough which can cause fatigue breaks.
I’ve also broken a flange on my 29 but I think it happened in the plane
I don’t think the issue is really spoke breakage, rather the lack of triangulation in the wheel and hence its ability to resist sideways force.
Imagine the extreme case that the spokes came vertically up from the centre of the hub – the wheel would not be able to resist any substantial side load before collapsing sideways (or at least flopping about). It isn’t such an issue with smaller wheels but with a 36" with a disc the triangle formed has a pretty acute angle at that side. You could imagine that hard cornering might be an issue.
As far as I recall spoke breakage is primarily due to lack of spoke tension rather than over tension.
And to add - I think the issue here is also that for 36” wheels spoke tension tends to be a lower than in smaller wheels - or perhaps I should say, when any spoke does go even slightly slack the impact is more noticeable than in smaller wheels with likely higher tensions.
Fundamentally the 125mm hubs just makes for a better triangle shape - benefits being: wheel tensioning, torsional forces / geometry, better rotor / disc brake clearance.
Down sights can be the wider stance - this can be overcome by training or not using Q-factored cranks.
These newer hubs are overbuilt in both 100mm and 125mm variants. But historically Schlumpf flanges were a bit notorious for being somewhat weak where spokes would pull through the edge of the holes - so I guess there’s also the background anxiety that building as flex free a wheel means a longer lasting hub.
I just have to get round to convincing Florian to make a Berd spoke hook-flange option - as that would then be even nicer to deal with
Man…after watching @toutestbon’s excellently made Pyrenee’s unicycle tour video, I’m having some doubts as to whether I want to proceed with a carbon G36er build.
So…TL;DR: I’m pivoting to a G29 P-frame build. Writing this to document my thought process and the build.
The fact of the matter is I only have money set aside for one Schlumpf build – my next, if there was one, would be some time from now after some long, hard work to save.
And the other fact is that I’d like to do more touring. I had intended to go on a tour across Utah, USA last Spring or Autumn. But after many obstacles, that never materialized.
The advantages/disadvantages of a 29/G29/36/G36 touring setup have been discussed ad nauseum on these forums so I won’t add to too much to that.
Overall, I felt comfortable with my pannier setup but felt there was room for improvement. For example, the bags bulging out into my thighs, despite wooden boards intended to flatten them down. Or the lack of water proofing. Or the need to pack the bags tightly (otherwise they swing wildly). And the awkward handling induced by such a weighty, bulky setup. It’s not an impossible way to travel – Ed Pratt took on the whole world with it. But he struggled a lot with hills and cities on such a setup.
Seeing as how Simon, @Becky98 and @Aurelien have chosen G29 setups for epic touring rides, I think it’s the clear choice and gives greater versatility choosing hilly routes.
It will still be an excellent racing machine at a higher cadence/shorter crank length (I was passed by many an unguni 29 at UNICON’s 10K ).
And I’m sure I’ll still have the pleasure of trying out a 36" UNICUS + Schlumpf 125mm, since @Elias and I have agreed to order our rims at the same time to spilt shipping/handling costs.
I think you made the right choice! I’m glad my film helped open your eyes
Of course, I love my G36, it’s an incredible racing machine that allows me to push my own limits. My G36 is capable of scaring me, just as it can make me reach a state of flow.
Yes, I’ll certainly miss the G36 for more localized exercise rides. I love the flow state it puts me in, too. But I’m sure I’ll build one up later on!
Hopefully I don’t pester you with too many questions about your build. Felix’s P-Frame build already has answered many of those.
I think the only choice I’m struggling with for now is rim + tire choice. I’d like to stick to the road as much as possible (95%) but have the option to hit gravel when options run out or I’d like getting away from traffic. Do you feel the Schwalbe G-One Speed performs well enough on gravel?
I’ve crossed the Pyrenees with the g-one speed, including a climb that’s considered gravel or MTB. But since then, I’ve been using a g-one allround 29x2.25. Let’s just say that it’s wet where I live, and as soon as you’re off the road it can quickly become slippery.
I think I’m pretty much ready to purchase a rim in the next day or two. But before I do so I wanted to consult the forums.
Since I’ve pivoted to a G29 build, I decided to go with a 100mm bearing spacing and 32H. (Sorry for all the previous discussion over 125mm & 36H. Hopefully others in the future can find such info useful for their own G36 build.)
I’m inclined to try out the LB XC925 rim, even if it’s intended as a XC tire, since it’s asymmetrical and the manufacturer recommended tire width allows for a 2.25" tire, such as the G-One Allround. If nothing else, I can be the guinea pig for this rim, giving others useful information if they chose to use this rim as well.
I’m somewhat put off from the WG44 since it would require a faux asymmetrical drilling and from the sound of it adds some lateral wind resistance.
I am happy I experimented with the WG44 and it fits my needs - so far riding better than expected but it isn’t a light rim.
Edit: just to add what swayed me most to the WG44 was their hybrid hook design - and I do wish they’d put that on more of their rims. Hookless is fine but I really liked the idea of a hybrid hook as this makes (from what I understand) for a better retention of tyres are higher PSIs - given that we can tend to need more PSI and have all our weight on one wheel - this was what clinched it for me over just hookless. Nothing wrong with hookless but it gets a lower PSI max rating.
After seeing Simon’s epic video it started making me realise that LightBicycle’s overly worried / cautious guidance (to me) around the rim needing to be really really strong was probably more a LB worry than one we should have - and we can see their rims hold up just fine in unicycle land and when carrying gear.
A naturally asymmetrical rim is nicer in terms of just piece of mind that it can be built well. But again lots of geared wheels have gone into symmetrical aluminium rims and fared perfectly well too.
For me I’m candid in that it is fun to obsess over the finer details of these things and if you’re spending the money it makes sense to get the best rim you can.
Whatever you do - don’t get the Full Tubeless option - no nipple access holes.
I got my wheel built, but it was such a pain and a hassle for me to do - about 1.5 days just lacing it as the nipples we’re very hard to hold in place and tighten - and as I doubt I’ll run tubeless any time soon, not worth it. You want a nice access hole to each nipple so that any repairs you make can be easily done. That’s the only regret or mistake I think I made with the WG44 order - as if I ever break a spoke or a nipple I’m in for a big repair hassle especially road side!
Do remember that LB will make rims set for 36h too. I went with 32h as that was what my hub was made to - as I got that hub for a Braus rim originally. But had I been buying it there and then I’d have gone with 36h as while more unusual I think I like the idea of being able to switch to a unicycle aluminium rim if I really wanted to - and LB offer 36h options in their rims so you’re not locked out of items.
Spoke count and wheel strength is moot really but options are nice.
Still you can’t go wrong really given it’s clear you’re using a carbon rim from LB.
These “decisions, decisions” are such a fun stage!
Ooh…yeah I skipped over that in my research. 35psi max is really low for road use. Hmm…I think I’ll continue my research before making a final decision.
As for 32H, I do feel safe in that regard. Most bikes these days have gone that direction, included fully loaded touring bikes. Of course, they have two wheels to spread the load. EDIT: I’m not too concerned with locking myself out of unicycle rims, since were I for some reason in need of a rim from a LBS while out on a longer tour I suspect they’d have greater availability of 32H options.
Yes, “decisions decisions.” Lots to ponder over, which is fun.
Just for documentation purposes, after researching some more and sitting with it I feel more settled on the AR25 and G-One Allround. Even if on paper it isn’t an ideal rim width + tire width combo, real world evidence shows it works. Plus, it gives a rounder tire profile, which can improve rolling resistance and handling on pavement.
Just to give you some more thinking, I use the AM928 with a 2.10" tire (the thunderburt I spoke about previously), and it works like a charm. It is good for cornering and straigth roads.
I believe using a thinner rim with a wider tire might not be the best choice available since it might be “too round” and thus not be comfortable on straigth roads.