In my experience both those questions are interrelated, and dependent on the riding you plan (and don’t plan but might end up doing despite those plans ;D) on doing. I don’t have much experience at 26", but I’ve been on a 24x3 since long cranks were in style and Profiles were state-of-the-art, and my riding preferences tend toward including technical uphill/downhill even if that also includes extended tech XC in between. In addition, much of my unicycling “career” has been trying to keep pace with bikes. I started on 24x3@160mm which was considered medium/short at the time, and continued with that length until quite recently. That length gave me okay (but still very “stairclimb-y”) cadence on the flats, decent climbing leverage, and decent “DIY” braking through steep technical downhills. Then when I got a magura (and the frame to support it), I swapped over to a set of 145mm cranks stolen from my trials wheelset, based partly on conversations here on the forums. I noticed a marked ease in carrying high cadence through the flats, and a predictable DEcrease in leverage on the downhills (which was countered nicely by my learning curve on the brake). What surprised me was the fact that once my feet “learned” where the pedals were at at all points in the smaller crank circle, my climbing actually improved.
This was confusing at first, but further cross-training with Ed’s KH29 and dual-hole 150mm/125mm cranks (and continued practice with climbing on the 24x3@145mm) has led me to a theory. I believe that the shorter cranks didn’t actually make climbing “easier” in terms of ability, but what they did was make it more efficient. The decreased leverage of the shorter cranks–some might say forces, others might say guides–you to pedaling “in circles” and learning to work WITH the momentum that you bring to the hill as well as the momentum you create mid-climb. The longer cranks allow for a cadence/stroke that essentially mimics climbing up stairs, where the left foot stomps down hard and settles at the bottom of the stroke, then the right foot stomps down hard, creating but subsequently destroying large amounts of momentum. This leads to a climbing technique that some have described as “chicken-like” as you chug, stop, chug, stop, chug your way up the hill, head moving roughly at a constant pace, but wheel moving herky-jerky under you.
The leverage afforded by the longer cranks and relatively low-rolling-momentum 24x3 tire allows this to work, because the tire can be REstarted fairly quickly every time (barring uneven-ness in the terrain), but it does create a fairly distinct dead spot in the power stroke. The lower leverage created by either decreasing the crank length, raising the wheel diameter, or both, doesn’t allow for the quick start-stop of the chicken dance uphill, and forces you (in almost every situation) to treat momentum as a precious resource to be gently cared for and nurtured ;). The hill will do its best to rob you of momentum, so it’s in your best interest not to aid it in that goal.
The pedaling “form” created by this lesson and transferred back to the 24x3 muni is (I believe) one of the factors in my increased ease and capability in steep and/or technical climbing in the past several months, and the recent addition of a virtual 36" wheel to my riding experience as of this past weekend may have taught me another lesson… Initially my reaction was to throw out every aspect of the chicken climb, because of its tendency to rob the precious momentum. It occurred to me, however, that the stomp portion of the stroke isn’t in itself a detriment to that commodity. The deal-breaker is really the continuation of the stomp into the “settle” at the bottom of the stroke. I’ll be working from here to try and create a hybrid cadence that involves pedaling circles but not SMOOTH circles, instead powering as hard as possible through say the front quarter of the pedal stroke, and easing off to a smooth circle for the crank-vertical portion of the stroke. This may allow me the best of both worlds, creating extra momentum above a smooth pedal stroke but never slowing the wheel myself. Perhaps it’ll still be a chicken, but with a mellowness… a white meat bird.
So to summarize (“lemme esplain… no there is too little time… lemme sum up” - Inigo, The Princess Bride), with the addition of brakes you can gain the benefits of easier high-cadence flats, easier circles on the uphill, and not suffer from the lower leverage on downhills. For a 26, I’d guess that to be somewhere in the 150mm on the short side or 165mm on the long, but based on my experience on the KH29 I’d probably recommend 150mm or dual-hole 150mm/125mm. I do highly recommend the brake if your riding will include steep descents, as it allows this tradeoff to work out much better in favor of flexibility.
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…I prefer dark, actually
billnye
John M