weak wheels?
The issue with 29" wheels is side to side strength. With the same hub the spokes form a narrower angle to the wheel, and the rim has more leverage against the spokes. A disc brake hub with a dished wheel makes it worse. Also the choice of tires for off road use is probably less than 10% of what's available for 26", especially in wider sizes. Something like a Rohloff internal gear hub that's large diameter, and has no dish for gears could make up for this. But that's about $1000 for the rear wheel alone. (That doesn't include the non-existent tires.) There are plenty of 26" 36 spoke wheels, and tires available. I f that's not enoiugh check out some tamdem builders for 40, and 48 spoke stuff. (Shimano Nexus hubs with 7-8 speeds aren't as strong, or expensive, and they're 36 hole.) It's probably "possible" to build a strong 29" rim, but if you can't get tires for it?????? Shwalbe has a wide 29er. I don't know who else, I think Gary Fisher uses Bontragers of some kind.