Project321 G3 Hubs
Stated Weight:
- Front: 155 g (Centerlock) / 175 g (w/ 6-Lock)
- Rear: 292 g (Centerlock) / 312 g (w/ 6-Lock)
MSRP (Hubset):
- Black: $650 USD / $875 CAD
- Color: $675 USD / $910 CAD
- Custom mix-and-match: $700 USD / $945 CAD
Configurations Available:
- Front: 110 x 15 mm Boost, 100 x 15 mm, 100 x 12 mm
Rear: 148 x 12 mm Boost, 157 x 12 mm Super Boost, 142 x 12 mm
Drive System: M-Pulse w/ magnetic pawls; 288 points of engagement
Intro
Project321 first showed off prototypes of their new G3 hubs at Sea Otter 2023, and the most attention-grabbing part of their design was the very slick 6-Lock rotor mounting system. But there’s a lot more going on with the G3 hubs than just the 6-Lock arrangement, including a revised version of their M-Pulse freehub mechanism with 288 points of engagement, a revised axle and bearing layout, and improved sealing. And they’re now made in Canada, too.
Let’s take a look at what Project 321 has cooked up.
Design & Options
Project321 offers the G3 hubs in 110 x 15 mm Boost, 100 x 15 mm non-Boost, and 100 x 12 mm front axle spacing, and with 148 x 12 mm Boost, 157 x 12 mm SuperBoost, and 142 x 12 mm non-Boost rear axles to fit most modern(ish) mountain and gravel bikes (fat bikes and DH ones with 20 mm front axles excepted). They’re available in 12 different colors, with the standard black option retailing for $650 USD / $875 CAD; going to a different colored hub shell bumps the price up to $675 USD / $910 CAD, and if you want to mix and match different colored end caps and / or 6-Lock flanges (more on those shortly) you can do so for $700 USD / $945 CAD.
6-Lock Rotor Mounting
The 6-Lock rotor mounting system is arguably the most novel (and visually obvious) way that the G3 hubs set themselves apart.
In short, the G3 hub shells are just configured for a standard Centerlock rotor. If you want to run those, go nuts — they mount up normally.
But if (like me) you prefer six-bolt rotors for their easier trailside serviceability and a greater array of rotor options, that’s where the 6-Lock system comes in. In principle, it’s just a different way of doing a six-bolt rotor adapter for a Centerlock hub, but in theory, it has some real advantages over a more conventional adapter (or a dedicated 6-bolt hub for that matter).
The way it works is pretty simple: there’s a stainless steel collet that snaps over the Centerlock splines on the hub, which includes threaded bosses to accept rotor mounting bolts. An aluminum flange slides over the Centerlock splines and onto the collet to support the rotor and transmit braking torque to the hub shell. A standard six-bolt rotor then bolts right up, and tightens the collet against the back side of the Centerlock splines on the hub shell to keep everything nice and secure.
Unlike a more conventional Centerlock adapter, the 6-Lock design means that you don’t need a bottom bracket or cassette tool to attach or remove the rotor, making trailside maintenance with a multi-tool more viable. Centerlock adapters also often have a slight amount of play in the interface, and the 6-Lock system should do away with that, too.
(The 6-Lock collet does use M4 bolts instead of the more conventional M5 rotor mounting ones, but Project321 includes custom ones with a T25 Torx head to make things easy. Finding replacements at a hardware store with that T25 head probably isn’t happening, but you should be able to make something work with an off-the-shelf bolt in a pinch.)
The 6-Lock design also means that the rotor bolts thread into a harder stainless steel piece (the collet) instead of a softer aluminum hub shell, making them harder to strip. And the collet is, of course, replaceable if need be.
M-Pulse Freehub Mechanism
The G3 hubs also get an updated version of Project321’s M-Pulse freehub mechanism. In short, it’s conceptually pretty similar to the earlier iterations that we’ve seen in the Project321 G2 hubs (and ones from Stan’s as well) but with faster engagement (now 288 points / 1.25° rotation, from 216 points / 1.66°).
The M-Pulse freehub uses pawls (eight of them, phased to engage in four sets of two each) and a ratchet ring inside the hub shell, which is normal enough, but unlike most pawl-driven hubs, which use small springs to push the pawls into place, Project321 uses magnets. The main idea is to reduce drag by lowering the amount of friction between the pawls and the ratchet ring as they click over from one set of teeth to the next.
Project321 says that the M-Pulse design makes for appreciably lower drag when coasting compared to a more conventional hub design, and they’ve worked on the axle and seal layout to improve things on that front, too.
Axles, Bearings, and Seals
The G3 hubs use a new axle design that Project321 says is stronger than the older version they used on the G2 hubs. The rear hub spins on four cartridge bearings (two for the freehub and two for the main hub shell) with dual-row bearings used in the higher-load portions for the more heavily loaded inboard position on both. And unlike most cartridge bearing hubs, the G3 features adjustable bearing preload to keep things free of play without undue friction and bearing wear. The new axle design has already been used in Stan’s M-Pulse hubs since 2022, but the G3 is the first Project321-branded hub to receive the update.
Some Questions / Things We’re Curious About
(1) Is the 6-Lock rotor mounting system really as easy to use and robust as it seems like it could be? (I got to play with a prototype at Sea Otter last year, and it seemed extremely promising. But we’ll need to get our hands on the production version to find out.)
(2) Is the reduced drag from the M-Pulse freehub design noticeable? How loud (or not) is the new 288 POE iteration?
(3) And how do the G3 hubs hold up long term? Adjustable preload hubs have, at times, gotten a bad reputation for coming loose, but it’s definitely possible to make a bomber one — Hadley being a prime example — and there are real upsides in drag and bearing wear from making things adjustable. How has Project321 done on that front?
Bottom Line (For Now)
Project321 has taken their time getting the G3 hubs to market, but the end result looks quite promising. We should start testing a set soon and will report back on how they perform and hold up once we’ve logged a lot of miles on them. Stay tuned for a full review to come.
I’ve got a set of G2s laced to Astral Serpentine Carbon rims with about a billion miles on them.
Unflappable, after replacing the early-days rear axle with the beefier version. These G3s look like they’ve improved even more in the sturdiness area.