Industry Nine Hydra 2 Single Speed ISO 6 Bolt Disc Hub
The Industry Nine Hydra 2 single speed is the Hydra 2 rear hub built for one gear: a dedicated single-speed driver with a short splined body and spacers to set chainline, the same phased six-pawl freehub on a 145-tooth ring for 870 points of engagement, and the Hydra 2's thicker axle and bigger bearings. Instant engagement matters more on a single speed than anywhere else, because there is no gear to spin up in; you stand and stomp, and the Hydra 2 is there. Industry Nine machines and anodises it in Asheville, North Carolina. This page covers the rear Industry Nine Hydra 2 Single Speed ISO 6 Bolt Disc Hub.
The Hydra 2 single speed comes from us only as a finished wheel: pick the rim, spokes and nipples, and we lace, tension and true it by hand in Georgia before it ships.
Design and construction
Industry Nine's engagement trick is phasing: six pawls sit at slightly different angles so that only one or two engage at any instant, which multiplies the 145 teeth on the drive ring into 870 engagement points. The Hydra 2 keeps that and makes the parts around it bigger. The axle is much thicker than the original Hydra's, which was the part that flexed under big riders; the drive-side shell bearing grew, and the freehub now sits on a spacer that keeps it from loading the pawls sideways. The seals are full-contact lips that keep water out without the drag of the old design, and the freehub uses lighter spring pressure, which is where the 60% cut in coasting drag comes from.
How it rides
A Hydra 2 engages before you have finished thinking about it. On a technical climb or a trials-style move there is no dead stroke, and because the engagement is phased rather than a single huge ring, the pickup is smooth rather than harsh. The new hub coasts noticeably freer than the original and the freehub is quieter, though still unmistakably an Industry Nine.
We build the Hydra 2 for trail, enduro, downhill and e-bike wheels; the thicker axle and bigger bearings make it a better e-MTB hub than the original.
Specifications
| Position | Rear |
|---|---|
| Axle options | QR 5x135mm Rear, Bolt On 10x135mm Rear, Thru Axle 10x135mm Rear, Thru Axle 12x135mm Rear, Thru Axle 12x142mm Rear |
| Driver bodies | Single Speed Shimano HG Cassette |
| Drillings | 32h |
| Spoke head | J-bend |
| Brake | 6-bolt disc |
| Left flange diameter | 59 mm |
| Right flange diameter | 68 mm |
| Left center-to-flange | 36.5 mm |
| Right center-to-flange | 37.5 mm |
| Spoke hole diameter | 2.6 mm |
| Weight | 295g |
| Material | Aluminum |
| Finishes | black, blue, bronze, gold, green, lime green, orange, pink, purple, red, silver, turquoise |
About this listing
What sets this listing apart from the other Hydra 2 single speed versions: 6-bolt rotor mount, QR 5x135mm, Bolt On 10x135mm, Thru Axle 10x135mm, Thru Axle 12x135mm and more, 32h drilling, about 295g, in black, blue, bronze, gold, green, lime green, orange, pink, . Pick the one that matches your frame and rotor and the rest of the hub is identical.
This is the 6-bolt Hydra 2 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 rear Industry Nine Hydra 2 Single Speed ISO 6 Bolt Disc Hub comes in the drillings listed on this page with the axle options shown in the configurator and a 6-bolt rotor mount. 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 Industry Nine's own Grade 300 and Sector rims and 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.
Build it into a wheel
This hub is live in our Custom Wheel Program for MTB single-speed and fat bike builds. Start a build with the Industry 9 Hydra 2 Single Speed ISO 6 Bolt Disc Hub and the configurator opens with this exact hub pinned at the top of the Industry Nine list — you choose the rest of the parts and it validates every combination as you go.
Testing, standards and warranty at Industry Nine
Industry Nine states it "has been anodizing & machining hubs, spokes, and drive systems in Asheville, NC since 2004" and that it engineers and manufactures every component of its hub and wheel systems in-house, including hub shells, axles, spokes and anodizing: "If it moves inside an I9 hub, we made it." Coverage of the Hydra2 launch (March 2025) reports Industry Nine drew on data from over 100,000 Hydra hubs in use to redesign the hub, with a 65% thicker axle "engineered for superior stress dissipation", larger 6903 bearings throughout, a labyrinth channel and full-contact radial lip seals against contamination. Industry Nine publishes no bearing-cycle, salt-spray, ISO 4210 or laboratory test figures for its hubs.
Hydra2 has 870 points of engagement at 0.41 degrees from a 145-tooth drive ring, and Industry Nine claims 60% less coasting drag than the original Hydra (690 points at 0.52 degrees). Launch material cites larger 5.5mm pawl pockets giving 26% improved force dissipation and says the hub is "specifically designed to handle the high torque demands of powerful E-bike motors".
Industry Nine's videos
Certifications
- Made in USA (Asheville, NC) — Industry Nine states hubs, spokes and drive systems have been anodized and machined in Asheville, NC since 2004; site tagline "HANDBUILT - ASHEVILLE, NC - KAMLOOPS, BC" (source)
- 5-year hub warranty — Parts, labor and return shipping years 0-2; parts only years 3-5; original purchaser; bearings excluded (source)
Sources on Industry Nine's site:
- About Industry Nine
- Industry Nine Warranty
- Industry Nine Hydra 2 Hubs (product page)
- Industry Nine Support Documents
- Industry Nine Hydra2 Support
Industry Nine publishes those results; ProWheelBuilder builds the hub into a wheel and does not test it in a lab.
Building it at ProWheelBuilder
Industry Nine makes the Hydra 2 single speed; ProWheelBuilder is an independent custom wheel builder in Georgia and not the manufacturer. We measure the rim before we cut a spoke, bring the wheel up in three or four rounds with a gauge, stress-relieve it between rounds and true it last, then tape it and fit a valve if you want it tubeless.
Only compatible hubs and spokes appear in the configurator, impossible combinations are struck through rather than hidden, and the price is live.
Warranty
Industry Nine's warranty. Industry Nine covers its hubs against defects in materials and workmanship for five years from purchase, with two years on the anodized finish. Its alloy and carbon rims carry a lifetime defect warranty to the original purchaser, with parts, labor and return shipping covered for the first two years and parts thereafter. Bearing wear, impact and crash damage are not defects.
ProWheelBuilder. Lace this into a wheel here and the finished wheel gets our own one-year warranty as well as the maker's. For twelve months we replace broken spokes however they broke, and the work on the wheel is on us - truing, re-tensioning, a rebuild where it is needed. If the rim or hub is covered by its manufacturer we put the claim in and chase it; if it is not, we supply an eligible replacement rim or hub at 25% off the current retail price. Carriage both ways is the customer's, and this does not cover wheels built from parts you send in.
Full terms are on our Policies & Warranty page.
Hydra 2 Single Speed 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 Hydra 2 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 Hydra 2 single speed from your bike type and weight.
Which freehub bodies fit the Hydra 2?
Shimano HG, SRAM XD and Shimano Micro Spline, swappable without tools and selectable in the configurator.
Is the Hydra 2 e-bike rated?
Yes. The thicker axle and larger bearings were designed with e-MTB loads in mind; tell the configurator it is an e-bike and it picks the spokes.
Which axle spacing does it fit?
QR 5x135mm Rear or Bolt On 10x135mm Rear or Thru Axle 10x135mm Rear or Thru Axle 12x135mm Rear or Thru Axle 12x142mm Rear. Measure between the inside faces of your dropouts if you are unsure, or text us.
Does it need special spokes?
No. It takes standard J-bend spokes, which the configurator offers in every gauge and finish we stock.
How long will the wheel take?
Build time comes down to parts availability rather than bench time. The estimated ship date is shown in the configurator before you check out.
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.
