Niner has built a devoted following by repeatedly showing the mountain biking world that our preconceived notions about 29 inch wheels are pretty much all wrong. The latest salvo fired in the aforementioned battle is the ROS 9 Mountain Bike Frame, a chromoly steel monster truck that's far from your average wagon wheeled hardtail. First of all, it's strong, not light. It's built to handle years of abuse under aggressive riders. That's a good thing, because the slack head angle and tight chainstays make it clear that it's built for going nuts on trail features, instead of chasing KOMs. Niner says it's the hardtail for riders who don't like hardtails, but we're more inclined to call it old fashioned fun, without the pretense. The ROS looks a lot like the SIR 9 from which it's descended, but the burly steel tubeset is far better equipped to handle bigger forks and wild riding styles. As a result, the ROS frame weighs in at 6 pounds, so it's no featherweight. But as anyone who's ever walked back to the trailhead due to a broken frame can tell you, a little extra weight is well worth the peace of mind, especially when you're jumping that gnarly double for the first time. A quick glance at the geometry sheet will confirm that the ROS isn't your average hardtail. Depending on your choice of a 120mm or 140mm fork, you'll end up with a 68 or 67 degree head angle, respectively. And in the world of 29ers, that's very slack perfect for going fast. Out back, the chainstays hover around the 16. 5 inch mark, with 5mm of foreaft adjustability courtesy of Niner's BioCentric bottom bracket. That keeps it turning on a dime, and makes full speed manuals a piece of cake. But it doesn't sacrifice stability with its roomy cockpit and low bottom bracket. A bike this burly isn't much good if you're stuck with flimsy components. That's where the 44mm head tube comes into play allowing compatibility with tapered forks. The 31. 6mm seat tube fits just about every dropper seatpost o...