As the popularity of Enduro racing rises, products made specifically for the segment are pouring out of MTB manufacturers left, right and center. Never one to be sleeping on the scene, SRAM has just announced their new 27.5” and 29” Rail 40 wheelsets which aim to provide the strength and stiffness needed for rough, fast descents without too much bulk to pedal up.
The new Rail 40’s represent the company’s ideal balance of strength, light weight, and width for charging aggressive all-mountain terrain. SRAM claims the wheels set a new benchmark in stiffness within their category yet offer excellent ride qualities for pointing it down and pushing it hard…
First of all, they are not 40mm wide. The model name doesn’t refer to width, the wheels are simply named in series with SRAM’s Rail 50 all-mountain wheels. Sram has a whole slew of trademarked terminology to describe the features of the Rail 40’s, so open up your MTB thesaurus and we’ll dive into the details.
The rims on the Rail 40 wheelset are UST Tubeless compatible, welded joint aluminum rims with an asymmetrical profile and SRAM’s ‘Taper Core’ technology. This refers to the construction of the rim’s sidewalls, which are reinforced along the wings to ensure good dent resistance but taper in along the center to keep weight in check. The rims also feature SRAM’s ‘Wide Angle’ 23mm profile which offers a reasonably wide but lightweight platform that maintains tire shape through aggressive cornering, preventing roll and providing great traction.
The ‘Double Time’ mechanism in the Rail 40’s rear hub is a four pawl design that grabs a 26 tooth ratchet ring, making for 52 points of contact. The mechanism smoothly achieves a 6.9 degree engagement without resorting to a design that uses tiny teeth or offsets the internal geometry, which the company says makes a more durable hub.
In a world of incompatibility, it’s nice to hear what SRAM has done with the spoke layout on this wheelset. Their ‘Solo Spoke’ double butted spokes are all one size throughout both hoops- Front/rear, drive/non-drive side? Aint nobody got time for that! They’re all of identical length, making life a lot easier when one pops.
The ’Speedball’ bearings are made to extremely tight tolerances by a factory that manufactures every part of the assembly in-house, making them more resistant to developing play and requiring adjustments. Cassette driver choices are either XD or 10speed, and of course there are plenty of hub options compatible with Boost 148. There’s quite a list of convertible axles, so rather than eloquently regaling them to you, here’s the data.
Front Hub: QR 9×100, QR Torque Caps, 15×100, 15×100 Torque Caps, 20×110, 15×110, 15×110 Torque Caps
Rear Hub: QR 10×135, 12×135,12×135 XD, 12×142, 12×142 XD,12×148, 12×148 XD
In their lightest possible setup, the Rail 40 wheels come in at 1810g for the 27.5” and 1900g for the 29ers.
Since there’s so many options available here’s the full chart with USA prices:
