Have you noticed that the inside of the wheel looks very different from the past? If the price of your new wheel is $2,000 or more, and you have a chance to see the inside of the flywheel assembly, you might see it. In a traditional wheel hub, 3 or 4 spring-loaded pawls mesh with the ratchet wheel or drive ring. The ring looks like a gear, but the teeth are on the inside of the gear, facing inward. As you can see from the picture of the DT Swiss DICUT hub, this new ratchet design has a pair of gears that mesh with each other, called a star ratchet. This design is called a "ratcheting" hub, and when this technology is deployed, it will replace the "ratcheting" hub. A confusing term is that the inverted gears you see on pawl and ratchet hubs are called "ratchet rings" by some people. Oh well! The function of any kind of hub is to allow your hub to slide when you are not pedaling, and to engage and drive the wheels when you pedal.
If you have heard of Hügi hubs, these are the earliest ratchet hubs. The design originated from the brain of the Swiss inventor William Hügi, and DT Swiss purchased Hügi (the hub company) and its patents. The reason you see so many ratchet hubs on wheels these days is that those related patents have recently expired. (When you see that everyone joins the design trend after the patent expires, you will realize that the patent holder has always been right.) The former professional triathlete-now the road marketing manager of DT Swiss- Ralph Eggert wrote to me that the general function of the ratchet is almost the same as the system found in some DT Swiss road and gravel wheels today and the DT Hügi hub. This is a video from DT Swiss that shows how the hub works.
As you can see, there are two gears interacting in the ratchet hub. This is the design that many wheel companies are now turning to. This is the case for all wheels manufactured by these companies today, except that DT Swiss recently adopted a new design with only a ratchet gear. “In 2019, DT Swiss introduced the Ratchet EXP free hub technology, where a threaded ratchet is firmly screwed into the hub shell,” Rolf wrote to me. "With Ratchet EXP, only one Ratchet rotates, but the meshing speed is the same and faster. In addition, because the bearing is located in the threaded ratchet, the bearing distance in the hub is also increased. This means that the axle is more rigid." Although large Most wheel companies have always deployed this hub style to their upper wheels, but DT Swiss has developed a ratchet hub for use on much cheaper wheels. These wheels use the RatchetLN free hub system, which replaces the 3-claw system even in the DT Swiss hub that will be used for entry-level bicycles. But at present, Ratchet LN is only applicable to MTB products (hubs and wheels). For road products, this FH technology will be launched at the end of 2022.
These are the hub styles you may be used to. What you see here is called the cartridge assembly or drive body, and they are usually interchangeable. They share the same internal structure, but the main body of the cassette is either Shimano style or SRAM XDR style (if 12-speed), and it is the main body of the SRAM XDR drive, as you saw in the DT Swiss video above. The above drive bodies have 3 and 4 pawls, or up to 6 pawls, you can see that the drive bodies with 3 and 4 pawls are made of different wheel brands. This is the design that these new ratchet hubs are gradually replacing. Which companies are turning to ratchet designs? ENVE uses Mavic ID360 ratchets in its wheels and is only suitable for road and gravel applications. The system has 40 teeth, 9 degree mesh. I just added some complexity there, didn't I? This is the state in a ratchet-type free hub system. Joint angle is a hot topic, but mainly in mountain bikes. Road riders don't need to worry so much. Just like the pawl and ratchet ring system, riders are always looking for faster engagement, also in this new hub style, by increasing the number of teeth of the star ratchet.
DT Swiss uses road wheels with 18 to 36 teeth. The engagement angle of the 18-tooth ratchet is 20 degrees (20° x 18 = 360°), which means that the pedal can be rotated up to 20° before the teeth are engaged. In the latest new version, DT Swiss deployed a 36-tooth star ratchet, so the meshing angle is 10°. If you look at what ENVE is doing, 40 teeth multiplied by 9° equals 360°. Therefore, more teeth means faster engagement. On the other hand, when descending or turning to turn, more teeth means more wear in the freewheel position. To prevent premature wear, the company uses special greases that have low viscosity and will not spread due to centrifugal force. This is why the wheel company warns you not to lubricate this system with just any grease.
Shimano refers to this style of deployment as Direct Engagement, and you will see it deployed in the hub shown in the image above. I wrote about this hub when I wrote about Shimano's new Dura Ace wheels. I like Shimano's expression of this design because it mixes a bit of old-fashioned ball and cage bearing design, allowing users to choose the weight of grease in the bearing and tighten the bearing (via a pair of tapered wrenches) to a precise degree. You will only find Direct Engagement on the new Dura Ace hubs and XTR and XT mountain bike hubs. Shimano did not simply adopt this design without testing. It creates prototype wheels with intentionally or lacking lateral stiffness, vertical stiffness, or driving stiffness. Almost all drivers like prototypes designed to increase driving rigidity, and Shimano learned that this is a design that must be followed.
Zipp has three hubs, which you can find in its premium wheels. There are 3 claws and 6 claws designs, but at the top of the stack is the cognitive center, which has what Zipp calls an axial clutch system. This is Zipp's view on ratcheting design, and here is a video that shows this very clearly. The picture above is a screenshot of the video, very cool, showing how Zipp uses magnets instead of springs. Zipp has been producing this hub for 5 years and was one of the first non-DT Swiss companies to adopt this type of technology (as far as I know). This is because Zipp's Cognition hub does not infringe DT Swiss's patents. In recent years, magnets have been removed from the Cognition hub and replaced by Sylomer wave springs. Another major difference of the Cognition hub is the larger diameter of the system, with 54 teeth in the ratchet or gear, compared to 36 more typically (or 40 as we saw in the ENVE case). CADEX and Reserve (which are the most commonly used wheel brands on Cervelo and Santa Cruz bicycles) also use this new hub style, and the list of brands using this method continues. You won't see this hub style in cheap wheels for a while (except for the version planned by DT Swiss), because making a star ratchet is not easy. For example, DT Swiss's single-star ratchet design, Ratchet EXP, encountered some surface finish problems, which caused premature wear and grief among some hub users. The star ratchet in the affected wheel must be replaced. Live and learn. Because the end caps of some of the wheels can be ejected directly-no tools are needed-my wheels are a bit fall apart in my hands. The cassette comes off with the inside of the hub. If you encounter this situation with a ratchet hub, just check the images and videos here. There is a spring on each side, and star ratchets that mesh with each other between the springs. Pick it up from the floor and reassemble it.
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