ONYX MTB LEFTY FRONT ISO 6 BOLT DISC HUB

Design and construction

The Lefty hub is built for Cannondale's single-sided fork: a large-bore shell that slides onto the fork's stub axle and clamps with a single bolt, with the rotor on the fork side. It uses the same sealed bearings and labyrinth seals as the rear hubs, which matters on a hub that carries the whole wheel from one side.

Machined and anodized in Minnesota. Truing a Lefty wheel needs the right adapter in the stand, which is one reason these come to a builder rather than a workbench.

This is the front hub, and a front hub has no freehub. What matters here is the part of the hub that carries the wheel: the bearings, the seals, the axle and the two flanges, and the front Lefty shares all of them with its rear partner. It is the simpler half of the pair and the one that runs longest between services. The driver and engagement story belongs on the rear hub's page; this page is about a front wheel that spins freely, stays sealed and builds stiff.

How it rides

It builds into a stiff front wheel on any 6-bolt disc rim.

On the road or the trail the front hub's job is to disappear: spin freely, keep water out, and hold the flanges still so the wheel tracks where you point it. The front Lefty does that with the same bearings and seals as the rear and none of the rear's complexity, and because a front wheel carries less load and no torque it stays true longer than the rear on the same rim. When the rear finally needs a look, the front usually does not.

Specifications

This listing

This is the 6-bolt version: Lefty 50mm, Lefty 60mm Super Max, Lefty 73mm Olaf, 32h drilling, about 200g, in baby blue pc, black ano, black aura pc, black matte ano, blu. Same internals and flanges as every other Lefty; only the mount and axle differ.

Six-bolt is the original disc mount and still the most universal: any ISO 6-bolt rotor from any brand bolts straight on, rotors are cheap and easy to find anywhere, and the six-bolt flange is a robust, simple interface that has been on mountain bikes for twenty-five years. Centerlock rotors do not fit it.

Sizes, fit and compatibility

The Onyx MTB Lefty Front ISO 6 Bolt Disc Hub comes in the drillings listed on this page and fits Cannondale Lefty forks with the current bolt-on axle interface; check your fork generation before ordering, and text us if you are unsure. J-bend spokes in any gauge; we build most Lefty wheels with Sapim Race or D-Light spokes or DT Competition and brass nipples.

It pairs with any 6-bolt disc trail rim in the catalog that matches its drilling. Give the configurator your bike type and weight; it picks a sensible spoke count and lacing pattern, which you can override.

Put it in a custom wheel

Build a custom wheel around the Onyx MTB Lefty Front ISO 6 Bolt Disc Hub — the link drops you into our Custom Wheel Program with this hub pinned, ready for you to choose the rest. It is set up for gravel and road disc, mountain bike, MTB single-speed and fat bike builds.

Building it at ProWheelBuilder

Onyx makes the Lefty; ProWheelBuilder is an independent custom wheel builder in Georgia and not the manufacturer. Every Lefty wheel we build gets spokes cut from the measured ERD of the rim, staged tensioning with a gauge, stress relief and a final true before it ships.

In the configurator you will only see parts that fit this drilling; combinations that are not made are struck through, and the price updates as you pick.