SRAM also offers transmission options for gravel bikes for all road bike groupsets. The range is correspondingly wide and extends from the favourable mechanical ensemble to the technically avant-garde wireless drivetrain. In recent years, the company has focussed on the development of the electronic twelve-speed Red and Force AXS groupsets. There is a relatively large price gap to the cheaper mechanical systems (eleven- and ten-speed).
SRAM is one of the pioneers of single drivetrains on mountain bikes and gravel bikes, every system can also be ridden with a chainring and there are matching cassettes. A special feature is that components from the mountain bike and road bike groupsets can sometimes be mixed, which means that huge gear ranges are also possible. The brakes are stable and function without complaint. The wearing parts only apply with the newer XPLR eTap AXS switching groups (in the Red, Force and Rival quality levels) are considered to be of high quality, but are relatively expensive.
Under the label GRX offers Shimano offers a wide range of special gears and disc brakes for gravel bikes. The quality ranges from low to high-end; as many parts can be easily combined, they are not always fitted to complete bikes. They can be roughly categorised into mechanical ten-speed and eleven-speed systems as well as the electronically shifting eleven-speed Di2. Otherwise, the differences between the GRX 400, 600 and 800 lie mainly in their weight and surface finish.
All variants can be ridden with one or two chainrings; the 1x10 combination is not recommended due to the limited number of gears. Extremely light gears can be realised in conjunction with the double chainring. The brakes of the Shimano GRX groupsets are considered to be finely controllable, but sensitive to grinding noises. Heavy riders should avoid the lightweight brake discs with aluminium core. All wear parts for Shimano gravel drivetrains are inexpensive and easy to obtain.
The Ekar, currently the only gravel bike drivetrain from Campagnolois high-quality, lightweight and comparatively expensive. The Italians have opted for a classic mechanical system without electronics, while the groupset is enhanced by a carbon crank and an advanced gear ratio concept. The 1x13 drivetrain is currently unrivalled and the wide-ranging sprocket set minimises the losses of the single chainring. The available gear ratios are more on the sporty side, while other manufacturers offer lighter mountain gears. The good ergonomics of the levers are much praised; several gears can be shifted at once using the characteristic thumb button. The brakes of the Campagnolo Ekar, developed in co-operation with Magura, are powerful, stable and easy to modulate. All wearing parts of the gravel bike gears are very durable, but the sprockets and chainrings in particular are expensive. One disadvantage is the limited choice of wheels, as the cassette requires a special freewheel.

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