Summary
Super Boost Plus is a rear frame-and-hub interface based on 12 × 157 mm spacing. It gives hub and frame designers additional lateral space that can be used for wider spoke bracing, drivetrain clearance, suspension packaging, and rear-triangle stiffness. The format developed from existing 157 mm downhill hardware and was adapted for trail, enduro, and e-MTB use during the mid-2010s.
Key Facts
Category: Hub and frame interface / Concept
Also known as: Super Boost 157, Super Boost Plus 157, 157Trail, SB+
Rear hub over-locknut dimension: 157 mm
Thru-axle diameter: 12 mm
Common chainlines: Approximately 55–57 mm, but frame-specific
Front hub spacing: Unaffected; Super Boost Plus is a rear standard
Used on: Selected trail, enduro, downhill, and e-MTB frames
Derived from: 12 × 150 mm and 12 × 157 mm downhill hub systems
Not directly compatible with: Boost 148 frames or hubs
Freehub options: HG, XD, or Micro Spline, depending on the hub
Primary potential benefit: More room for hub-flange and frame packaging
Overview
Super Boost Plus describes a 157 mm rear dropout and hub interface adapted for non-downhill mountain bikes. It is 9 mm wider than Boost 148, but that difference alone does not guarantee a stronger wheel, wider tire clearance, shorter chainstays, or a stiffer frame. Those outcomes depend on how the manufacturer uses the available space.
The standard appeared as long-travel 29ers, enduro bikes, and e-MTBs placed increasing demands on rear wheels and frame packaging. Large wheels increase leverage on spokes, wide tires compete with chainrings and chainstays for space, and suspension pivots or motor housings can make the bottom-bracket region difficult to package.
A 157 mm rear end gives designers more lateral room in which to solve these problems. Hub manufacturers can move one or both spoke flanges outward. Frame engineers can create wider pivot structures, reshape chainstays, or establish additional tire and chainring clearance.
The trade-off is a smaller component ecosystem. A Super Boost Plus bike requires a 157 mm rear hub and a frame-specific thru-axle. Its crank and chainring must also produce the chainline specified by the frame manufacturer.
What the Standard Defines
Super Boost Plus primarily defines the distance between the rear hub’s outer endcap faces: 157 mm. The frame’s dropout spacing must match that dimension, and the hub must accept a 12 mm thru-axle.
“12 × 157 mm” does not fully specify the axle itself. It does not define:
- Overall axle length
- Thread pitch
- Threaded engagement length
- Axle-head or washer design
- UDH compatibility
- Lever or tool interface
A 12 × 157 mm axle from one frame may therefore be unsuitable for another 157 mm frame. Pivot, for example, sells model-specific 157 mm axles and directs owners to confirm fitment against the bike’s schematic. Pivot 157 mm UDH axle information
The standard also does not determine the front hub. A Super Boost Plus bike may use a conventional Boost 110 front hub or another interface specified by its fork.
Relationship to 150 and 157 mm Downhill Hubs
The 157 mm dimension existed on downhill bikes before the term Super Boost Plus was adopted for trail and enduro applications. It evolved from the 12 × 150 mm downhill format.
In common downhill implementations, 150 and 157 mm hubs used similar hub shells, cassette positions, and drivetrain chainlines. The 157 mm system added approximately 3.5 mm of dropout support on each side through different endcaps. This helped locate the wheel during installation and provided a broader dropout interface.
That history does not mean every 150 mm hub can be converted to 157 mm. Conversion depends on the hub shell, axle, bearings, and endcaps supplied by the hub manufacturer. Some hub families support an endcap conversion; others do not.
The trail-oriented use of 157 mm places more emphasis on exploiting the available width for spoke-flange placement and frame packaging. Knolly describes this interpretation as “157Trail.” Knolly 157Trail technical overview
Hub Flanges and Wheel Stiffness
The distance between the hub’s spoke flanges influences spoke bracing angle. Moving a flange farther from the wheel centerline creates a wider spoke triangle, which can improve lateral wheel stiffness.
However, hub over-locknut dimension and flange spacing are not the same measurement. Two 157 mm hubs can have substantially different flange locations.
The drive-side flange is constrained by the cassette and freehub body. Hub designers have more freedom on the non-drive side, where they may choose to:
- Move the flange outward for a wider bracing angle
- Position it inward to improve left-to-right spoke-tension balance
- Pair the hub with an asymmetric rim
- Balance bearing placement, flange diameter, and hub-shell stiffness
A legacy 157 mm downhill hub may physically fit a modern 157 mm frame yet use relatively conservative flange spacing. It may therefore provide little or none of the wheel-stiffness advantage claimed for a purpose-designed Super Boost Plus hub.
Wider flange spacing primarily affects lateral bracing and wheel stiffness. It should not automatically be described as increasing torsional stiffness, since torque transmission also depends on flange diameter, spoke pattern, spoke count, rim construction, and spoke properties.
Chainline and Q-Factor
Super Boost Plus is frequently associated with a wider chainline, but 56.5 mm is not a universal requirement. Depending on the frame and crank system, specifications commonly fall between approximately 55 and 57 mm.
Race Face notes that 157 mm frames are most often designed around a 55 mm chainline, while individual manufacturers may specify a different figure. Race Face crank and chainline guide
Chainline is the lateral distance from the bicycle centerline to the center of the chainring. Q-factor is the distance between the outer pedal-mounting faces of the crankarms. They are related packaging measurements, but they are not interchangeable.
A wider chainline does not necessarily require an unusually wide pedaling stance. Crank manufacturers can alter spindle length, crankarm shape, or chainring offset independently. Shimano’s FC-M9130-1, for example, combines a 56.5 mm chainline with a listed 171 mm Q-factor.
The correct setup is determined by the frame or e-bike motor manufacturer—not by hub spacing alone. A suitable crank installation must provide:
- The specified chainline
- Adequate crankarm-to-chainstay clearance
- Adequate chainring-to-frame clearance
- Correct bottom-bracket and spindle compatibility
- An acceptable Q-factor for the bike and rider
Direct-mount chainring offset labels are interface-specific. A “0 mm,” “3 mm,” or “6 mm” ring from one crank manufacturer should not be assumed to produce the same chainline on another crank system.
Drivetrain Compatibility
A Super Boost Plus frame does not inherently require a special rear derailleur or cassette. The derailleur aligns to the cassette through the frame’s hanger or UDH interface, while the cassette fits the hub’s freehub body.
The drivetrain must still be checked as a complete system:
| Component | Compatibility requirement |
|---|---|
| Frame | Must use 157 mm rear dropout spacing |
| Rear hub | Must have compatible 157 mm endcaps and axle bore |
| Thru-axle | Must match frame length, thread pitch, head, and UDH arrangement |
| Freehub | Must match the cassette: HG, XD, Micro Spline, or another specified interface |
| Cassette | Must match the freehub, chain, shifter, and derailleur |
| Derailleur | Must match the drivetrain and frame hanger or UDH interface |
| Crank | Must clear the frame and produce the required chainline |
| Chainring | Must match the crank interface, chain, chainline, and frame clearance |
| Brake rotor | Must match the hub’s six-bolt or Center Lock interface and required diameter |
| Spokes | Must be calculated from the actual hub flange and rim dimensions |
A UDH-equipped 157 mm frame may support SRAM Transmission, but 157 mm spacing alone does not establish Transmission compatibility. The frame must have an approved UDH interface and the required structural and dimensional provisions.
Frame-Design Effects
The additional rear width can give frame designers more space around the chainstays, tire, chainring, suspension pivots, and motor housing.
Potential uses include:
- Wider pivot bearing placement
- Straighter or more widely separated chainstays
- Additional tire or mud clearance
- Clearance for wider chainlines
- More space around an e-bike motor
- Improved heel or crankarm clearance through targeted shaping
- Wider spoke-flange placement
These are design opportunities rather than automatic features. A poorly optimized 157 mm frame may have no more tire clearance or rear-end stiffness than a well-designed Boost 148 frame. Likewise, short chainstays remain dependent on wheel size, suspension layout, tire clearance, chainring size, and frame construction.
Advantages
Potentially Stronger Rear Wheels
A purpose-designed wide-flange hub can increase spoke bracing angle and lateral wheel stiffness. This can be useful for 29-inch wheels, heavier riders, aggressive enduro use, and e-MTBs.
Frame and Suspension Packaging
The wider rear end gives designers more room for pivots, chainstays, tires, chainrings, and motor housings.
Established Gravity-Bike Foundation
The 157 mm dimension has a long history in downhill applications, so suitable hubs and heavy-duty wheel components already exist.
Drivetrain Flexibility
Standard Shimano and SRAM drivetrains can be used when the correct freehub, cassette, hanger, chainline, and crank components are selected.
Limitations
Reduced Wheel Availability
Boost 148 remains more common in the trail-bike market. Complete 157 mm wheels and replacement hubs may be harder to find locally.
Frame and Hub Incompatibility
A 148 mm hub cannot normally be converted into a 157 mm hub with simple external spacers. Only hub models explicitly designed for conversion should be modified.
A 157 mm hub also cannot fit inside a 148 mm frame without replacing or redesigning major components.
Chainline Confusion
Selecting a crank solely because it is advertised as “Super Boost compatible” can still produce the wrong chainline. The frame’s specified measurement must be confirmed.
Model-Specific Axles
The 157 mm spacing and 12 mm diameter are not enough to identify a replacement axle. Thread pitch, shaft length, UDH arrangement, and axle-head design remain frame-specific.
Possible Pedaling-Clearance Trade-Offs
Some implementations use wider crank spindles or Q-factors. Whether that is necessary depends on the frame and crank design.
Mechanic’s Perspective
Super Boost Plus problems are usually compatibility problems rather than faults in the basic standard. Before ordering parts, a mechanic should record the bicycle’s exact model year and verify the frame manufacturer’s technical documentation.
The most important checks are:
- Confirm that the frame is genuinely 12 × 157 mm.
- Identify whether the dropout uses a conventional hanger or UDH.
- Obtain the frame-specific axle specification, including thread pitch.
- Confirm the hub’s endcaps and axle bore.
- Identify the freehub body before selecting a cassette.
- Check the frame’s specified chainline.
- Verify crank spindle, bottom-bracket, and chainring compatibility.
- Measure chainring, crankarm, and tire clearance before final assembly.
- Calculate spoke lengths from the actual hub and rim dimensions when building a wheel.
- Align the brake caliper and recheck derailleur indexing after installing a different wheel.
Common workshop symptoms include:
| Symptom | Likely cause |
|---|---|
| Wheel will not seat fully | Incorrect endcaps, axle, or dropout interface |
| Axle begins threading but binds | Wrong thread pitch or engagement length |
| Chain is noisy in the largest cassette cogs | Chainline too far outboard |
| Chain is noisy in the smallest cogs | Chainline too far inboard |
| Chainring contacts the frame | Incorrect ring offset, spindle, or chainring size |
| Crankarm contacts the chainstay | Incorrect spindle or crank model |
| Rotor rub appears after a wheel swap | Hub tolerances or caliper position differ |
| Derailleur indexing changes after a wheel swap | Cassette position differs slightly between hubs |
| Replacement wheel feels less laterally stiff | New hub has narrower flange spacing or different wheel construction |
| Spokes cannot be reused with a new hub | Flange diameter or center-to-flange dimensions changed |
A mechanic should never identify the axle solely by measuring the gap between the dropouts. Axle length and thread specification must be taken from the frame documentation or an accurately identified original axle.
The same caution applies to chainrings. “Boost,” “Super Boost,” and offset markings are not sufficiently precise unless the crank model and resulting chainline are known.
For a replacement wheel, the most reliable approach is to match:
- Hub over-locknut dimension
- Endcap type
- Axle bore
- Freehub body
- Rotor interface
- Spoke count
- Flange dimensions
- Cassette and rotor positions
Even when two wheels meet the nominal 157 mm standard, small manufacturing differences may require brake-caliper adjustment or derailleur re-indexing.
Buyer and Builder Checklist
Before purchasing a Super Boost Plus frame, wheel, hub, crank, or chainring, confirm:
- Exact frame model and model year
- 157 mm rear spacing
- Conventional or UDH dropout
- Axle length and thread pitch
- Required chainline
- Bottom-bracket shell and bearing standard
- Crank spindle diameter and length
- Chainring interface and offset
- Maximum chainring and tire sizes
- HG, XD, or Micro Spline freehub
- Six-bolt or Center Lock rotor interface
- Availability of replacement endcaps, axles, and freehub parts
For riders who travel frequently or race, carrying the frame’s specific spare axle can be sensible. A generic shop may stock 157 mm hubs or wheels without having the correct axle for every frame.
Notable Implementations
Pivot
Pivot has used Super Boost Plus 157 on selected Switchblade, Firebird, Trail 429, and Shuttle platforms. Exact axle and UDH compatibility varies by model generation, so Pivot’s frame schematic should be checked before ordering parts.
Knolly
Knolly uses the term 157Trail across several trail and enduro platforms. Its technical documentation emphasizes wide-flange wheel construction and chainlines in the 55–57 mm range. Current Fugitive specifications, for example, call for 12 × 157 mm spacing and identify 56.5 mm as the preferred chainline. Knolly Fugitive specifications
Other Manufacturers
Selected models from Devinci and other mountain-bike manufacturers have also used 157 mm spacing. Compatibility should always be checked by model year because manufacturers may change rear spacing, chainline, or dropout design between frame generations.
Common Misconceptions
“Every 157 mm Hub Produces a Stiffer Wheel”
False. Wheel stiffness depends on flange placement, rim construction, spoke geometry, spoke count, tension, and build quality. A 157 mm hub with conservative flange spacing may not offer the expected bracing advantage.
“Super Boost Plus Requires a DH Crank”
False. Many trail cranksets can produce an appropriate 55–57 mm chainline. Clearance and the frame manufacturer’s specification determine the correct crank.
“It Always Has a 56.5 mm Chainline”
False. Although 56.5 mm is common on some frames and cranksets, other Super Boost Plus bikes specify approximately 55 or 57 mm.
“A Wider Chainline Always Means a Much Wider Q-Factor”
False. Chainline and Q-factor can be adjusted separately through crank, spindle, and chainring design.
“It Requires a Special Rear Derailleur”
False. The derailleur must match the cassette, shifter, and hanger system—not the hub width by itself.
“Any 12 × 157 mm Axle Will Fit”
False. Axle length, thread pitch, axle head, and UDH compatibility are frame-specific.
“A Boost Hub Can Be Spaced Out to Fit”
Generally false. External spacers cannot safely create the required axle support, cassette position, rotor position, and hub geometry. Use only conversions explicitly approved by the hub manufacturer.
“Super Boost Plus Automatically Creates Shorter Chainstays”
False. It gives designers additional packaging room, but the resulting geometry depends on the complete frame and suspension design.
Related Terms
- Boost 148
- 157Trail
- Hub Spacing
- Thru-Axle
- Wheel Dish
- Spoke Bracing Angle
- Chainline
- Q-Factor
- Direct-Mount Chainring
- Universal Derailleur Hanger
- SRAM Transmission
References
- Knolly Bikes: 157Trail Technical Overview
- Race Face: Crank Selection and Chainline Guide
- Shimano: FC-M9130-1 Product Information
- Pivot Cycles: 157 mm UDH Rear Thru-Axle
- Frame manufacturer service manuals and model-specific axle diagrams
- Hub manufacturer flange-dimension and conversion documentation
- Professional wheel-building references covering spoke bracing angle, dish, and tension balance