Onyx MTB SS Rear ISO 6 Bolt Disc Hub
The Onyx Classic SS is the Onyx Classic with a dedicated single-speed driver: the heaviest-duty sprag clutch Onyx makes, instant and silent, with the extra sprag rows and bearing capacity that let it take the abuse a single-speed rider puts through a rear wheel standing on every climb. Machined and anodized in Minnesota, with a short splined driver and spacers for chainline, centerlock or 6-bolt rotor mounts and Boost or standard spacing. This page covers the Onyx MTB SS Rear ISO 6 Bolt Disc Hub.
The Classic SS is not sold bare. You choose the rim and the rest of the build in the configurator, and it ships from our shop in Georgia laced, tensioned and trued by hand.
Design and construction
The Classic SS pairs the heaviest-duty sprag clutch Onyx makes with a dedicated single-speed driver. The extra sprag rows and bearing capacity exist for exactly this use: a single-speed rider stands on every climb, and every one of those efforts goes into the hub without a derailleur or a cassette shift to soften it.
Machined and anodized in Minnesota, in a catalog of more than twenty colors plus a limited release each month.
How it rides
A Classic SS engages the instant you stomp with no dead stroke and coasts in silence, and its extra sprag rows mean it never skips under the torque a single speeder produces. It is heavier than the Vesper SS and stronger; for a single-speed trail bike ridden hard or a heavy rider, the Classic SS is the Onyx hub we recommend.
Specifications
| Position | Rear |
|---|---|
| Axle options | QR 5x135mm Rear, Bolt On 10x135mm Rear, Thru Axle 12x135mm Rear, Thru Axle 12x142mm Rear, Thru Axle 12x148mm Boost Rear |
| Driver bodies | 1 Single Speed Shimano HG Cassette (Aluminum) (+$45), 2 Single Speed Shimano HG Cassette (Steel) |
| Drillings | 28h, 32h, 36h |
| Spoke head | J-bend |
| Brake | 6-bolt disc |
| Left flange diameter | 60 mm |
| Right flange diameter | 60 mm |
| Spoke hole diameter | 2.6 mm |
| Weight | 454g |
| Material | Aluminum |
| Finishes | baby blue pc, black ano, black aura pc, black matte ano, blue ano, blue candy pc, clear ano, gold ano, green ano, green anti freeze pc, green florescent pc, green kawasaki pc, orange ano, orange florescent pc, pink ano, pink florescent pc, purple ano, purple candy pc, red ano, red candy pc, turquoise ano, white pc, yellow cardinal pc, yellow florescent pc |
This listing
This is the 6-bolt version: QR 5x135mm, Bolt On 10x135mm, Thru Axle 12x135mm, Thru Axle 12x142mm and more, 28h, 32h, 36h drilling, about 454g, in baby blue pc, black ano, black aura pc, black matte ano, blu. Same internals and flanges as every other Classic single speed; only the mount and axle differ.
This is the 6-bolt Classic single speed: the rotor bolts to a flange with six T25 bolts, which is the mount most mountain and gravel rotors still use and the easiest to find a rotor for on the road. If you run centerlock rotors, choose the centerlock version of the same hub instead.
Sizes, fit and compatibility
The Onyx MTB SS Rear ISO 6 Bolt Disc Hub comes in the drillings listed on this page with the axle and rotor options shown in the configurator. The single-speed driver takes standard splined cogs with spacers to set the chainline. J-bend spokes in any gauge; we build most single-speed wheels with Sapim Race or Strong spokes or DT Competition and brass nipples.
It pairs naturally with any trail rim in the catalog that matches its drilling. Pick single speed as your bike type in the configurator and it recommends a spoke count and lacing pattern.
Put it in a custom wheel
Build a custom wheel around the Onyx MTB SS Rear 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, track and road single-speed and MTB single-speed builds.
What Onyx says about testing
Onyx Racing Products hubs are made in the USA by a division of Christianson Systems in Minnesota; in a 2020 interview the company described itself as "Minnesota made and owned". Hub shells are machined from 7075 aluminum (retailer listings cite 7075-T651 with heat-treated stainless steel and titanium hardware), and Onyx's European distributor states Onyx freehub units "are made out of high-grade 7075 aerospace-grade aluminum in the USA". Bearings are hybrid ceramic on the Classic line and an upgrade option on Vesper; the distributor states "Since early 2025 all Onyx hubs have been assembled with high-quality Japanese EZO bearings." Onyx specifies a grease service temperature range of -58°F (-50°C) to 248°F (120°C). It publishes no bearing-cycle, salt-spray, ISO 4210 or load-test figures. Onyx's specifications state radial lacing is not permitted on any Onyx hub and set a maximum spoke tension of 120 KgF.
the patented sprag clutch is a one-way clutch of cams between two races, giving instant engagement, instant disengagement when coasting and silent operation; BMX hubs use a single-row sprag assembly, mountain, road and gravel hubs a double-row assembly. Onyx publishes no numerical torque capacity; its distributor states Classic hubs "are e-bike approved for bikes that have a mid-drive unit with a peak power output of up to 1500W."
Onyx's videos
Inside the Onyx shop
Certifications
- Made in USA (Minnesota) — Onyx states it is "Minnesota made and owned"; retailer and distributor listings state "Made in the USA" (source)
- 5-year limited hub warranty — Hub 5 years to original owner; sprag clutch 1 year against manufacturing defects; wheel builds 1 year (source)
- E-bike approval (Classic hubs) — Distributor states Classic hubs are e-bike approved for mid-drive units with peak power output up to 1500W (source)
Sources on Onyx's site:
- Onyx Racing Products - Tech (site returned 403 at time of research)
- Onyx Racing Products - Limited Warranty (U.S. Only)
- Onyx Racing Products Wheels - Warranty
- November Bicycles: In their own words - Onyx Racing Products (April 17, 2020)
- Onyx Hubs Europe - Technology
Everything in this section is published by Onyx. ProWheelBuilder is the wheel builder, not the tester, and the hub reaches us as the maker ships it.
Building it at ProWheelBuilder
Onyx makes the Classic single speed; ProWheelBuilder is an independent custom wheel builder in Georgia and not the manufacturer. Every Classic single speed 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.
Warranty
Onyx's warranty. Onyx Racing Products covers its hubs under a five-year limited warranty against defects in materials and workmanship.
ProWheelBuilder. Wheels we build around this part are covered by our own one-year warranty alongside the maker's. Within the year: broken spokes replaced regardless of cause, and the labor on the wheel - truing, re-tensioning or a complete rebuild - included. A manufacturer-covered rim or hub failure is a claim we make and manage for you; one they will not cover is answered with an eligible replacement at 25% off retail. Shipping each way is yours. Parts you supply yourself fall outside it.
Full terms are on our Policies & Warranty page.
MTB SS Rear ISO 6 Bolt Disc Hub questions
Will my rotors fit this hub?
This is the 6-bolt version: any ISO 6-bolt rotor bolts straight on with six T25 bolts, which is still the most common and the easiest rotor to replace anywhere. Centerlock rotors do not fit it - for those, take the centerlock version of the same hub, listed separately.
Which spokes and nipples suit the Classic single speed?
For most riders a double-butted spoke such as Sapim Race or DT Competition with brass nipples; lighter riders can go to Sapim Laser or CX-Ray. The configurator recommends a gauge and count for the Classic single speed from your bike type and weight.
Classic or Vesper?
Classic for downhill, e-bikes and the heaviest duty; Vesper for cross-country, trail and enduro where its 23% lower weight matters.
Is the Onyx Classic e-bike rated?
Yes. It is one of the few instant-engagement hubs rated for e-MTB use.
Which drivers fit the Classic?
Shimano HG, SRAM XD and Shimano Micro Spline, selectable in the configurator.
Why is a sprag clutch silent?
There are no teeth. Hardened steel cams wedge against a smooth race when you pedal and release when you coast, so there is nothing to click.
Which axle spacing does it fit?
QR 5x135mm Rear or Bolt On 10x135mm Rear or Thru Axle 12x135mm Rear or Thru Axle 12x142mm Rear or Thru Axle 12x148mm Boost Rear. Measure between the inside faces of your dropouts if you are unsure, or text us.
Not sure? Text or leave a voicemail on 470-253-0929 or email info@prowheelbuilder.com — you will be talking to the people who build the wheels.
