It won’t change how or where you ride, but WRP’s unassuming and hidden Zero Drag Kit brings silence and measurably less drag to some of the world’s most popular and common rear hubs.
Regardless of drivetrain brand or riding discipline, there are options to suit any hub that uses DT Swiss’ original Star Ratchet, Ratchet LN, or newer Ratchet EXP systems. And in most cases, you won’t even need tools to make the swap.
It’s been almost six months since I first started testing the WRP Zero Drag Kit in a DT Swiss 350 hub. This review takes a look at the tech and offers insight into whether this upgrade is worth the not-so-minimal price tag. Spoiler alert, it’s almost certainly cemented a place in my Favourite Things list for later this year.
Lows: High price for a small part. More parts to, in theory, go wrong. Pushes out freehub by 1 mm, making the cassette more prone to fall off with the wheel out of the bike. Very rare pop noise when going from backward roll to forward power (though no slipping).
Price: AU$370 (approx US$240) for DT Swiss EXP. AU$430 for DT Swiss Star Ratchet (approx US$280). International shipping from US$30.
An intro to WRP
Williams Racing Products, aka WRP, has been making waves in the gravity side of mountain biking for a few years. Based near Geelong, Victoria, and neighbour to the likes of Partington and Baum Cycles, Mic Williams is a mechanical engineer with a background in BMX and mountain bike racing.
Williams Racing Products got its start with custom-machined stems and then progressed into aftermarket rocker links to adapt popular mountain bike frames for mixed wheel setups (aka, mullet). I first met Williams through the Trinity MTB bike project, and his designs and ideas have been quickly growing in complexity, such as the derailleur-in-a-can gearbox and CentreHub.
However, among all of that, Williams teased a DT Swiss Star Ratchet upgrade a few years back. One that would bring a zero-drag and zero-noise mechanism to any hub running DT Swiss’ popular internals.
It’s a system that you can tell is in use when a rider on a DT Swiss hub coasts silently. World Cup downhiller Troy Brosnan is one rider suspected to be using it, and multiple-time Enduro world champion Richie Rude is another with suddenly mysteriously quiet hubs. And it’s not just the pro mountain bikers buying them, either.
The hubs don't have to be DT Swiss' own, either. Brands such as Roval (Specialized), Hollowgram (Cannondale), and Reserve (PON) all produce wheels with DT Swiss ratchet hub internals.
While everything else in the WRP catalogue remains largely centred around gravity mountain bikes, the Zero Drag is one that reaches many facets of cycling, and arguably makes even more sense for performance-focused road and gravel riders looking for a quiet ride.
Explaining DT Swiss’ ratchet design and WRP’s mod
Originally acquired under the Hugi name, DT Swiss’ Star Ratchet system has been around for decades. With two independently sprung ratchet rings, the system gained a reputation for best-in-class reliability. While most pawl-based hubs on the market put all the pedalling load through small points of contact, the Star Ratchet system engages with full cylindrical contact.
When coasting, the angled geometry of the ratchet rings causes them to separate. The two rings remain in rubbing distance of each other, and the clicking you hear while coasting is the peaks of the teeth knocking over each other (see video). Pedal forward, and the teeth catch, coaxed in by the axial springs.
Such clever geometry and springs formed the key selling feature of many DT Swiss hubs, something still commonly found at the centre of countless brands of wheels (the biggest examples being DT Swiss, Reserve, and Roval). Over the years, the patented Star Ratchet system was also commonly found inside other brands of hubs from the likes of Bontrager, Lightweight, Syncros, and many more. Older 190, 240, and 350 hubs will almost certainly be of the original Star Ratchet variant, while 370 hubs from 2021 and newer are also Star Ratchet.
In recent years, the expiring patent saw DT Swiss innovate on its legendary Star Ratchet and introduce Ratchet EXP – a system that fixed one of the sprung ratchet rings in place, aiming to save weight and widen bearing spacing. It also introduced more noise, which some love and many hate. It remains a more premium option in DT Swiss’ line-up, limited to higher-end road, gravel, and cross-country models such as the latest 240s and 180s.
That brings us to the WRP Zero Drag Kit. There are two variants, one designed for the original Star Ratchet hubs (including cheaper Ratchet LN), and another for the newer Ratchet EXP hubs. Currently, the newest DEG MTB system is not supported. Both options are direct-fit replacement internals for the respective hubs and provide 36T (10 degrees) of engagement (inline to the latest Star Ratchet and Ratchet EXP hubs).
There is some wizardry at play with the patent-pending design, but in a nutshell, it uses a series of tiny magnets to keep the ratchets further apart when coasting, just far enough that they’re no longer in contact, and therefore not causing drag or noise while you’re not pedalling. Pedal forward, and those steel rings lock together just like the original design, once again, aided by an axial spring. In addition to the magnets, there is also a secondary ratchet (which sees no pedalling load) that serves to separate the ratchets from each other – done with a small kick.
That kick is not unlike some freecoaster BMX hubs, where the smallest of back pedal movement disengages the hub’s ratchet mechanism. In almost all riding situations, the mere act of stopping pedalling and the momentum from the cassette is enough to kick the system into its disengaged “zero drag” mode. See the video below.
While not exactly the same, similar attempts have been made by companies such as Shimano (with its short-lived Sylence hubs) and the seemingly impossible-to-buy Foss Zero Drag hub. However, Williams managed to overcome some critical design limitations of those, and do it in a down-scaled system that fits into hubs people already have.
Word of warning. With the original Star Ratchet patent expired, the past few years have seen an increasing number of DT Swiss-copy products on the market that use a Star Ratchet-type system that looks like the original. However, looks can be deceiving and many of these are dimensionally different to DT Swiss’ products. Do your own research to ensure your ratchet hub is using authentic DT Swiss internals (for example, the latest ratchet system hubs from Giant/Cadex and Hunt are not compatible).
Installation
If you’ve ever serviced a DT Swiss Star Ratchet hub, then you’ll be very comfortable with installing the Zero Drag kit.
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