Industry Nine Hydra 2 MTB Rear ISO 6 Bolt Disc Hub
The Industry Nine Hydra 2 is the second generation of the hub that made instant engagement mainstream, and it fixes the things people complained about on the first one. It still has the phased six-pawl freehub, now on a 145-tooth steel drive ring for 870 points of engagement, which is 0.41 degrees of crank rotation before the wheel picks up. What changed is everything around it: a 65% thicker axle, deeper pawl pockets, a spacer between the shell and freehub that cuts shear loads roughly in half, bigger 6903 shell bearings with full-contact lip seals, and about 60% less coasting drag. Industry Nine machines and anodises it in Asheville, North Carolina, in every color it makes. This page covers the Industry Nine Hydra 2 MTB Rear ISO 6 Bolt Disc Hub.
The Hydra 2 is built to order here. Choose the rim, spokes and nipples in the configurator; the wheel leaves Georgia laced, tensioned and trued.
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.
The hubshell is machined from aluminum bar with J-bend flanges in 28 and 32 hole, anodized in Industry Nine's full color range, with centerlock or 6-bolt rotor mounts and end caps for Boost, Superboost and standard spacing. Freehubs swap between HG, XD and Micro Spline without tools.
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 5x141mm Boost Rear, Thru Axle 12x148mm Boost Rear, Thru Axle 12x150mm Rear, Thru Axle 12x157mm Super Boost Rear |
| Driver bodies | Shimano HG 8,9,10,11 & Road 12spd, SRAM XDR 10,11 & Road & MTB 12spd, Shimano Micro Spline 12spd |
| Drillings | 28h, 32h |
| Spoke head | J-bend |
| Brake | 6-bolt disc |
| Left flange diameter | 59.5 mm |
| Right flange diameter | 62 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 |
Which version this is
Version notes. 6-bolt rotor mount, QR 5x141mm Boost, Thru Axle 12x148mm Boost, Thru Axle 12x150mm, Thru Axle 12x157mm Super Boost, 28h, 32h, about 295g, in black, blue, bronze, gold, green, lime green, orange, pink, . If your frame or fork uses a different standard, the other versions of the Hydra 2 on this site cover it.
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 Industry Nine Hydra 2 MTB Rear ISO 6 Bolt Disc Hub comes in the drillings listed on this page with the axle, rotor and driver options shown in the configurator. J-bend spokes in any gauge; we build most Hydra 2 wheels with Sapim Race, D-Light or CX-Sprint spokes or DT Competition and brass nipples, and Industry Nine also sells a straight-pull version for its own alloy spokes.
It pairs naturally with Industry Nine's own Grade 300, Triad and Sector rims, and with Reserve, ENVE, We Are One, Nox, DT Swiss, Race Face and Stan's rims that match its drilling. Tell the configurator your bike type and weight and it suggests a spoke count and lacing pattern to suit.
Build it with us
We build this hub to order. Open the Custom Wheel Program with the Industry 9 Hydra 2 MTB Rear ISO 6 Bolt Disc Hub already selected and pick the parts around it; it is offered for mountain bike, fat bike and tandem and e-bike builds, and the configurator will not let you assemble a combination we would not build.
Industry Nine's testing and certifications
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.
Warranty: Industry Nine states "Hubs are covered for five years against defects in materials and workmanship." Years 0-2 include parts, labor and return shipping; in years 3-5 parts are covered and labor and shipping may apply. Warranties apply to the original purchaser only with proof of purchase from a certified dealer; bearings and other normal wear items are excluded. Industry Nine says service needs only basic tools, "no proprietary tools are required".
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 in Asheville, North Carolina; ProWheelBuilder is an independent custom wheel builder in Georgia and not the manufacturer. The build is the same every time: measured ERD, spokes cut to the half millimeter, staged tensioning with a gauge, stress relief, a final true, and tubeless tape and a valve on request.
The configurator shows only rims and spokes that fit the Hydra 2's drilling and color, strikes through combinations that are not made, and prices the wheel 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. If we lace this into a wheel for you, that wheel also carries ProWheelBuilder's own one-year warranty, which covers broken spokes regardless of cause and all wheel-related labor, including truing and rebuilding, for a year from purchase. Where a rim or hub is covered by its maker, we make the manufacturer's claim for you and coordinate it; where it is not, we offer an eligible replacement rim or hub at 25% off current retail. Shipping to and from us is the customer's. This cover does not extend to wheels built from components you supply yourself.
Full terms are on our Policies & Warranty page.
Hydra 2 MTB 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.
What changed from the Hydra to the Hydra 2?
A 65% thicker axle, bigger shell bearings with full-contact seals, deeper pawl pockets, a spacer that cuts freehub shear loads, engagement up from 690 to 870 points, and about 60% less coasting drag.
Is 870 points of engagement too much drag?
Not on the Hydra 2. Industry Nine cut spring pressure and improved the seals so it coasts freer than the original Hydra despite the higher engagement.
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.
Is ProWheelBuilder the manufacturer of the Industry Nine Hydra 2 MTB Rear ISO 6 Bolt Disc Hub?
We are not. Industry Nine manufactures the hub; ProWheelBuilder's part is the wheel: measuring, lacing, tensioning and truing it here in Georgia.
Which axle spacing does it fit?
QR 5x141mm Boost Rear or Thru Axle 12x148mm Boost Rear or Thru Axle 12x150mm Rear or Thru Axle 12x157mm Super 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.
