The new Sram "Rail 40" wheels are made to withstand aggressive all-mountain and enduro excursions. Despite their stiffness and stability, at 1,810 in 27.5 inches and 1,900 grams for the 29-inch wheelset, the wheelsets are within a moderate range and are only marginally heavier than the Rail 50. In terms of price, however, the Rail 40 are very interesting. Updates on this will follow as soon as the Swiss prices are available.

The Rail-40 aluminum rim has the UST standard and is therefore fully tubeless compatible. The rim does not need to be sealed with rim tape. The rim profile is asymmetrical and the material is reduced in the less stressed areas. This enables Sram to achieve a light rim weight while maintaining stability. The rim has an inner width of 23 millimetres to ensure that the tires remain stable on the rim even when cornering aggressively.

Boost for normal tire sizes
The new 148-millimeter axle standard "Boost" was developed to support the rim wider on the hub and thus achieve greater lateral stiffness. In other words, Sram started this development before plus-size tires became an issue.
The flange is 3 millimeters further out on each side of the hub. The length of the straight-pull spokes is the same on both the drive and brake side, which makes servicing easier.

The pawls of the freehub engage in 52 ratchets inside the hub.
The freehub of the hub conceals a 4-pawl design. Two of them engage simultaneously in the 26-tooth ratchet ring. The other two pawls are each in half, which enables faster engagement. In addition, Sram promises high durability of the freewheel.
As an option, Sram offers the possibility of adapting the hub of the Rail-40 wheel to the respective rear triangle dimensions using different end sleeves. The hubs are also still 10-speed compatible.www.sram.com