The new DT Swiss 240 hubs feature their Ratchet EXP system, integrating the driveside bearing into the threaded ratchet ring to increase axle stiffness by a claimed 15% whilst reducing wear.
The DT Swiss 240 hub has been one of the most popular hubs on the market for years. Chances are, if you’ve bought a relatively high-end set of hoops then you will have had a wheelset with this hub or on with ‘240 internals’.
DT Swiss have just announced a refresh of the 240 hub, one that sees some small changes to the external shell and a change to the rear driveside bearing that DT Swiss claim improves stiffness and reliability.
The changes centre on the use of DT Swiss’ Ratchet EXP system. This moves the rear driveside bearing outboard, placing it inside the threaded ratchet ring. What you get from this, DT Swiss says, is a claimed “15% improvement in axle stiffness.”
Two of the key things that you want from your rear hub are snappy engagement and long, hassle-free service life. The new 240 has moved to a system that requires only one spring to align the ratchets where the previous system required two conical springs. This, DT Swiss claim, “results in faster full engagement and eventually reduces wear.”
We’ve seen the DT Swiss ratchet system inside their hubs for a few years now. They’re not the only brand to use this freehub engagement method and DTSwiss says that one of the reasons that they chose a ratchet over a pawl design is the larger surface area created to transfer drive force. “The full engagement of the ratchets creates a large contact surface and therefore low surface pressure that leads to superior reliability.”
“What makes the Ratchet System superior is the fact that all teeth on each of the ratchets engage simultaneously every time. In comparison, the engagement surface of pawl hubs is rather small.”
DT Swiss also points out that fewer parts result in a lighter hub, with the new rear hub starting at a claimed 212g where the old 240 rear hub started at 221g.
The 36 teeth on the ratchet give you an engagement angle of 10º. DT Swiss says that this is rather important as it influences the ‘backlash’. In DT Swiss’ words, this “is the maximum idle distance the crank can turn before the freewheel mechanism engages and converts the force on the crank into acceleration of the wheel.”
“The backlash is influenced by three factors, the crank length, the gear ratio and the engagement angle. The crank length and the engagement angle are proportional to the idle distance of the crank. The gear ratio, on the other hand, has an inversely proportional effect on the backlash”.
A rather long definition but why does this matter? Well, if you’re jumping back on the power out of a corner in a criterium, you want instant acceleration. A smaller backlash results in faster drive engagement and faster acceleration. They’ve even got that fancy equation, so you can calculate yours at home.
Having more points of engagement would, DT Swiss say, result in a reduction in backlash and therefore faster acceleration. However, they suggest that there would be a weight penalty.
“If we were to introduce a system with more points of engagement we would need to enlarge the construction of the hub what eventually would lead to a significantly higher weight”.
So they say that they’ll be sticking with the 36T ratchet as they claim it “represents the best optimisation” when reliability is also considered. Should you be really keen to reduce backlash, you can buy a 54T conversion kit that takes the engagement angle down to 6.7°.
If you’ve ever tried to pull end caps out of a hub, you may well have struggled get purchase on the smooth metal surface. DT Swiss has included a very simple notch on the lip of their end caps. DT Swiss claim that “the newly developed shape of the end caps simplifies disassembly significantly and therefore makes the maintenance even easier.” It’s a nice touch for the home mechanic.
The new DT Swiss 240 hubs are available in road and MTB versions for J-bend and straight-pull spokes. Road versions can be ordered with a Shimano 11-speed freehub or Sram's XDR driver and come in both disc and non-disc variations. Campagnolo freehub conversions are available separately.
Front Road Disc - £159.99
Rear Road Disc - £314.99