So I recently acquired a schlumpf 29er (the road/square-axle version, 'coz it was much cheaper!), and after a while trying (none too successfully) to ride it with 125 cranks, I’ve now put 140s on it. The difference is tremendous, it’s controllable but I can cruise along at huge speed compared to previous ungeared 29"/26" unis I’ve tried…(14-16mph doesn’t even seem fast…!)
However, I am wondering about putting the 125s back on at some point. My feeling is that I’d not only need generally much better balance etc., but also I’d want a much lighter wheel - as is, it just takes too long to do anything 'coz you have so little leverage. (Yeah, ok - or my legs just aren’t strong enough:) ). At present I have the Nimbus 29er rim and a Kenda Karma folding tyre - iow, the lightest rim available from UDC, and about the lightest 29er tyre going also.
Hence, I’m wondering about going much narrower - and accepting that this’ll be a largely road-only machine. Maybe a 1.6" tyre or so - I don’t think I want anything quite as extreme as the Bacon Slicer or Road Razor, but Nimbus 28er-ish, perhaps; I was thinking of maybe a Schwalbe Marathon Racer, which in 700C*38mm weighs 425g (compared to the Karma’s 600ish!). However, I’d also want to move to a lighter rim, and I’m worried about rim strength: one can easily get 29er “Mountain bike” rims weighing in the 400g range, but presumably these are built to withstand only half the weight of a rider on them, rather than the rider’s whole weight being on one wheel. “Tandem” rims are probably designed for equivalent weight (maybe even more, given the weight of the bike, tho generally not for off-road usage), but are often just as heavy as e.g. the nimbus 29er, and frequently have 48 spoke holes (not an option!). Narrower rims may be stronger for the same weight, but I’m wondering what experiences other RSU readers have had in this field???
I use 125s on my schlumpf, and I know what you mean, it is a bit of a beast. But you do get used to it.
One thing that might make a big difference for road riding is using a slick high pressure tyre, they’re much better, you’ll get much more resistance from knobs even on a light weight muni tyre. I’d consider first trying a lighter weight smooth tyre (whilst it isn’t ideal, you can run a tyre on a too wide rim without problems).
For road riding, any strong 36 hole road rim will be fine, that’s what everyone used to use before the KH & nimbus rims came out. They don’t run the big apple nicely, but are fine with narrower tyres. You also remove much of your ability to do muni, as muni tyres suck a bit on the narrower rims. I used to use a mavic touring rim on my 29er.
If you do end up trying the rim change, if you could report back on how it goes, that’d be great, I’ve been kind of considering something along these lines.
My 29er has a Mavic T520 rim on it that’s just 19mm wide, half the width of a Nimbus! I don’t know how much it weighs but it’s not a lot.
It’s pretty versatile, I’m using it with a Kenda Klaw 2.1" at the moment and it’s the only problem I’ve noticed is that the tyre folds over a bit if I try to hop up something steep sideways. That’s obviously not going to be a problem on a road uni!
As far as strength goes it’s been fine so far despite being second-hand. Bike rims are designed to take half the rider’s weight, plus half the bike’s weight (which could be quite a lot on a touring bike!), and go over bumpy roads at much higher speeds than unicycles do. I’d definitely reccommend a bike rim if you want a light road 29er, if you don’t like the narrow bike tyre you could always use a Big Apple 2.0" on a rim like mine, at the pressure you need for road riding it should be fine.
I’d guess that the wheel build is more important than the actual strength of the rim. Probably a good idea to use a decent quality rim (box section, eyeletted) and probably not an ultra-narrow racing rim (although MikeFule’s Open-Pro is holding up OK as far as I know, even with some mild off-roading), but bike rims are stronger than people think - although unicycling does put more sideways stress on rims than bicycling, so putting more importance on the wheel build quality.
compared to previous ungeared 29"/26" unis I’ve tried…(14-16mph doesn’t even seem fast…!)