Test Crankbrothers Synthesis Gravel Carbon: The gravel offshoot of the MTB wheelset is designed for robustness; aerodynamics play no role here. With its low weight and high rigidity, it can also inspire those who otherwise prefer deep rims.
The accessories specialist is going in a completely different direction with its wheel sets than most suppliers of road bike and gravel wheels. Which is no surprise, because Synthesis has its roots in MTB sport - and there, aerodynamics are of secondary importance. The Crankbrothers Synthesis Gravel Carbon is therefore designed completely differently than the typical carbon wheel set for gravel bikes, which is almost always somehow "aero" with 30 to 50 mm deep rims and as few flat spokes as possible.
Let's start with the rims: As mentioned, they are made of carbon and are very flat at 21 mm. They are also quite wide - the inner width is 26,5 mm and the outer width is 31 mm. This means that the rims are optimized for 40-48 mm wide tires, although anything from 30 to 55 mm can be mounted. However, only tubeless tires can be used, especially since the rims are designed without hooks, which optimizes the tire fit. But the Schwalbe G-One RS are not significantly wider than the nominal size of 40 mm.
Light, flat rims with large rim width
Now you might think that Crankbrothers is aiming for the lowest possible weight with its flat carbon rims. At 1.522 grams (manufacturer's information: 1.544 grams), the wheelset weighs about as much (or as little) as models with 40 mm deep aero rims. Part of this weight goes into the 28 round spokes that connect the rim and hub in a triple cross pattern; the manufacturer probably used the rest to make the rim more stable. This can be seen in the additional material used to reinforce the nipple seat. With a weight of 365 grams (manufacturer's information), a Synthesis carbon rim is still pretty light.
Anyone who ventures into difficult terrain with their gravel bike should have a good chance with this wheel set. But what about comfort and smooth rolling behavior? According to the manufacturer, this is also an advantage of the flat carbon rims.
Low rotating masses
As is typical for hookless bikes, fitting the tires is straightforward, meaning the wheelset is ready to ride quickly. The first time you set off, you can see that the power transmission is top-notch, and the competitive weight also has a positive effect on the ride characteristics. The "rotating masses," which should be as small as possible, especially on the outside of the wheel, are rather small here.
In terms of shock and vibration absorption, the Synthesis Gravel Carbon cannot noticeably stand out from the aero competition; at 2 bar, the smooth Schwalbe G-One RS smooths out even rough gravel tracks. Those who put on more robust tires with a stiffer carcass for rough terrain may be more likely to feel the "compliance" that the manufacturer speaks of. On the other hand, the Synthesis does not feel any slower at typical gravel speeds than wheels with deep rims - so much for "aero", which only becomes an issue at sustained speeds of over 30 km/h. It is noticeable that the wheelset provides a lot of safety when leaning, even if the tire pressure is not too high; this is where the wide, hookless rims prove their worth.
Great for many tempo changes
Of course, it is impossible to say whether this wheel set can withstand loads that would break others. But it does make sense that the flat carbon rims are more stable than similarly heavy aero models. And that makes the Crankbrothers Synthesis Gravel Carbon ideal for anyone who wants maximum robustness with the lowest possible weight. And its light rims should prove their worth when changing speed frequently - those who keep going will benefit more from a low rim weight than those who ride at a constant pace.
Speaking of acceleration: The fact that the toothed disc freewheel engages in 10° increments is not something that is necessarily annoying when you let the bike roll and then pull on the chain again. Freewheels with finer pitches may be nice, but in practice their reduced free play is hardly noticeable. This aspect should not stop you from being interested in the Crankbrothers Synthesis Gravel Carbon. At 749,99 euros for the front wheel and 849,99 euros for the rear wheel, the solid wheel set is not exactly cheap. If you want to start small, you can also get the Synthesis Gravel with identically dimensioned aluminum rims - then the front and rear wheels together cost less than 600 euros, but also weigh a good 1.900 grams.