The YBB (“why be beat”) rear softtail design really does its job. It takes the edge off the vertebrae-crunching hardtail feel on those trails with divots left by collapsed gopher tunnels and the like.
Not paying attention for a moment? The YBB saves your ass— literally. More important, your back will thank you. If you’re in your 20’s maybe no big deal, but as life progresses, such things are a BFD.
Having now ridden the YBB and the sibling Mooto X hardtail, there is no question that the YBB is to be preferred. The hardtail is just a hint more responsive under power, but when the bumps hit hard the YBB makes all the difference.
26" or 29er?
I compared the 26" and 29er YBB designs. It’s amazing how the wheel-size difference is so dramatic. The 29er feels like a monster truck compared to the petite 26" wheels.
The 29er rolls over stuff that the 26" requires more finesse on; the 29er just makes it easy and fast to cover ground once up to speed.
Spinning up a 29er at low speeds is another matter. With an 11% greater circumference, getting up to speed is noticeably more sluggish— an 11% greater circumference means 24% more power is needed to spin up the wheels, by F=mV^2. The power required is not 24% of the total since body and bike weight are dominant, but it’s quite significant in feel.
To gain the quick feel of a 26" ride, a 29er demands a light wheel with light tires, or you’ll be faced with a bike that feels sluggish to accelerate. On the flip side, greater wheel momentum will carry you over more of the nasties on the trail.
I’m torn— the agile feel of the Moots YBB 26" is fantastic, but the Moots YBB 29er just gobbles up the trail when up to speed.
The 29er tires also soak up bumps and the small stuff better, rolling more easily over tricky patches. It was much easier to ride through a patch of lose 4" cobblestones with the 29er.
Hardtail Mooto X
The hardtail was a great ride— fantastic, but demands much more attention to the trail, and forces more standing on the pedals to compensate for the lack of rear “give”.
Compared to dual suspension
For the really rough stuff, dual suspension is a huge advantage (I’ve owned both a top-end Specialized and the Trek Top Fuel).
But long ago I mastered the finesse required for riding a hardtail over the rough stuff, and the Moots YBB offers an ideal compromise without the weight and complexity of full dual suspension. I’m strongly inclined towards the YBB approach— beats a hardtail, and keeps the bike simple and quick and elegant too.