> I have begun the process of building my own MUni (Mountain Uni), planned
> to have a 26" wheel, 36 spokes, 175mm crankarms.
>
> A wide rim be stronger than a narrow rim & should provide better support
> for a wide tire than a narrow rim, right? Considering that more than double
> the load of the typical ATB wheel will be placed on the MUni wheel, I believe
> I should try to get the strongest rim possible.
Well, the carbon fibre uni was always concieved as a MUni, with a 26"
wheel. The rim I use is the bog standard Mavic M231, just like about 50%
of all mountain bikers. Its narrow compared to the steel rims that
unicycles normlly use but being ally, the strength to weight ratio is
sooo much higher that strength is not a major problem. On this rim I've
done lots of hoping, curbs and stair-riding with no probs whatsoever.
However, the 17mm steel axle has just cracked :-)
On a mtb, two things destroy rims. The first is the wearing through of
the breaking surfaces, not relevant on a uni. The second is impact
loading out of the plane of the wheel. This, to use that lovely american
expression, 'tacos' the wheel. Unless you're heavily into doing stairs
while side riding I can't see that happening. On a uni the load is
vertically down, through the wheel and consequently its a very durable
structure.
There's also the effect of speed. At 30 to 40 mph+ the loading on a rim
because of rough ground is lots and lots higher than the loading in a
Muni rim. Unless you're planning on that kind of speed, then I bow down
before you oh mighty one.
As for tyre fit, mtb tyres are designed for the 20mm rims most mtbers
use. It looks odd at first but I've never had a tyre peel off, even when
jamming tight tarmac. (Well, tyre peel off road, but thats different.) My
uni alternates between a Specialised Nimbus semislick for road use and a
Panaracer Smoke 2" for the dirt. Don't go for anything excessively knobbly
like a Storm Control 'coz you don't need that much grip and the knobbles
cause that 'wheel advancing only an integral no. of knobbles' feeling.
As for Mavic 281's, I use one of the back of my thrashy mtb. Unless
you're planning on doing 2' dropoffs then I think its overkill. Get a 231
'coz their cheap and strong enough.
Jez
jpw24@cam.ac.uk