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Hit the rails.
Whether you call them 650b or 27.5, this mid-size wheel standard has been making waves in the mountain bike market. And because so many of the mid-wheel bikes cater to aggressive trail use, SRAM built the RAIL 50 27.5in Aluminum UST Wheel. The RAIL wheels are light enough for long climbs, but they really shine on the descents, where their stiffness keeps you on track, even on the roughest of trails.
In designing its new range of wheelsets, SRAM's engineers started with a blank slate. Accordingly, they focused on building wheels that provide durability, a responsive ride quality, and a light overall weight. The Taper Core construction of the aluminum RAIL rim is an illustration of this mission. Taper Core is the product of an extrusion process that allows SRAM to place more material where it's needed for durability. This results in a thinning of the remaining rim profile in order to optimize the balance of weight and strength. In fact, a cross-section of the rim reveals that its main cavity is thinner on the sides than either the bead hook or the spoke bed. In other words, the sidewall thins gradually, providing a strong base for the bead hook. This way, the rim is more resistant to denting under hard impacts.
The cross-section of the RAIL 50's rim also reveals an asymmetrical shape that offsets the spoke bed. However, this isn't a mere novelty. Instead, it's actually key to building the RAIL wheels with zero dish, while simultaneously maintaining even spoke tension. Basically, with a traditional symmetrical rim, the spokes on the drive side must be shorter in order to keep the rim centered relative to the dropouts. Unfortunately, though, the discrepancy in spoke length puts greater tension on the drive side spokes than the non-drive side spokes. As a result, this imbalance reduces the overall strength of the wheel. However, in the case of an offset rim design, like the RAIL, the spoke bed aligns with the hub shell. This keeps both the spoke tension and spoke length equal on both sides, while the shape of the rim centers the tire relative to the dropouts. This way, the RAIL wheels maintain correct spacing and reap the benefits of even spoke tension. And remarkably, this is achieved with identical spoke lengths on both sides of the hub, at both the front and rear. This not only adds strength, but it also means that one replacement spoke is able to be used on the on any side of either the front or rear wheel.
The balance that the RAIL's offset rim design provides means that these wheels will provide plenty of stability. However, SRAM uses a wide rim profile in order to carry that stability over to your tires as well. SRAM's Wide Angle rim shape provides a 23mm internal width. So, your tires will remain planted through hard turns, not roll off of the rim. And, along with the wide rim profile, the RAIL rim uses UST standard bead hooks for an easy tubeless setup. But, unlike a true UST rim, there are holes drilled in the rim for the spoke nipples. This means that you'll need to apply tubeless-approved sealing tape if you're planning on running a tubeless setup.
At the center of the RAIL 50 wheels, you'll find user-friendly hubs. A straight-pull spoke design is employed, as opposed to a traditional J-bend spoke. As a result, stiffness was improved, while also adding the benefit of making on-the-fly spoke replacements a bit easier. The axles use push-on end caps at front and rear, meaning that fitting these wheels to nearly any mountain bike axle standard will be a breeze. The freehub is available in both a standard 9/10-speed configuration, as well as SRAM's XD freehub body. And regardless of the version, both freehub designs run on DT Swiss's Star Ratchet system. Not only has the Star Ratchet system earned a reputation for light weight and durability, but its design enables home mechanics to overhaul the rear hub without any proprietary tools.
The SRAM RAIL 50 27.5in Aluminum UST Wheel is sold individually and in a 27.5-inch wheel compatibility. Please note that the rear wheel is available with either a Shimano/SRAM 9/10-speed freehub body or a SRAM XX1-compatible free hub body.
- Item #SRM0536