I would get a wider rim such as the KH26 or tryall rim (both 47mm). You can also get the 29" KH drilled rim. Or whatever you think you’ll like better… But for a 2.7mm wide tire I really wouldn’t want to have such a narrow rim.
Even for a light xc setup, unless it’s just gonna be on-road, a wide rim will give much better control and a better feel. Go with a drilled rim to keep the weight down, kh has nice options in 26 and 29. If you plan on using a superlight xc tire, the wider rim will also help to keep it from folding, and you can stay light w/o things feeling skittish
First of all, I am really interested in this and not trying to just argue for the sake of it.
I have a KH 29" XC rim (38mm), and I find it to be a good ride generally. I understand from some of the other rim width discussions that as the rim gets wider the tire can have more influence from road crown, or trail camber. I was thinking about maybe getting the new wider KH 29" freeride rim (47mm), but as I thought about it more I decided to stick with what I have. I already find myself compensating for deep camber in narrow singletrack I wonder if it wouldn’t be worse with the wider rim.
There is a point where the wheel just gets squirly with a narrow rim. Add to that the inevitable tire folding, and I think you would just not enjoy the ride. I can’t see a rim narrower than the KH XC rim being much good for a trail uni. I would guess that as the wheel diameter and tire width get smaller you might be able to get away with a narrower rim.
Since I got a Schlumpf 29er, I’ve been using that for big-wheel trail rides, but prior to that I was using a unicycle named Zippy, a Semcycle XLW frame with a 25mm rim and a Schwalbe Big Apple (29x2.35"). It’s just fine for XC stuff; light and responsive. If I were doing exclusively trail riding, I would put a slightly knobbier tire on it, but I don’t think a wide rim is necessary or even desirable if you’re not doing drops.
I would strongly recommend a 29" over a 26" for light XC; it’s more fun to be going faster.
I don’t know where you got that. I think it is the other way around. A narrower rim will have the tyre fold more, which is the effect that through some physics makes the uni want to drift down on a cambered road.
General question: when you folks in this thread quote rim width, is that internal or external width? I think the internal width is the dimension that matters in this respect, but you can’t measure it when the tyre is mounted and inflated and so ideally you measure it while naked. (You yourself may wear clothes though.)
My thoughts are that you will probably want a wider rim if you are doing any kind of off road riding. In my experience a DX32 (32mm inner 38mm outer) is just too narrow for a 3" tire and I still had some folding issues with a 2.7. It works great with a 2.5 though.
I now use a 46mm wide Echo rim which is great but I wish it was just a tad wider for my 3" Gazz.
Alternately you could opt for a slightly skinnier tire to match the thinner rim. A 26X2.5 is a great XC size
There have been a number of threads discussing tire width, tire profile, and rim width. I was having a terrible time with road crown, and so I did a bunch of searching, and read every post that came up regarding road crown drift. On more than one occasion I read post’s that indicated a rounder tire profile helps with the problem, and that a narrower rim helps to produce a rounder tire profile thereby helping to prevent drift. On the other hand it would most likely produce a higher profile making folding the sidewall more likely.
In support of your point, it makes sense that folding a sidewall would make the problem worse as it would lead to a flatening of the tire profile. So, in the end I would assume that there is a happy medium, and that the tire choice and pressure will have some bearing on how wide you could go with the rim.