Introduction to Mountain Bike Hub Standards
In the world of mountain biking, hub spacing standards have undergone significant evolution, driven by the desire for stronger, stiffer wheels and improved frame geometry. The transition from older standards to Boost and then to Super Boost was a direct response to the demands of modern riding, which includes larger wheel sizes and aggressive trail features. Understanding the difference between Boost and Super Boost is crucial for any rider looking to build a new bike, upgrade components, or simply understand how their bike is designed to perform.
The Rise of Boost: Improving Wheel Performance
Boost is a hub spacing standard that quickly became the industry norm for most mountain bikes after its introduction. It's defined by a 148mm rear axle width and a 110mm front axle width. This was an increase of 6mm at the rear and 10mm at the front compared to the previous 142mm standard. The primary benefit of Boost was that it allowed for wider hub flanges, which in turn improved the spoke bracing angle. A wider spoke bracing angle creates a stronger, stiffer wheel laterally, which is particularly important for larger 27.5-inch and 29-inch wheels that inherently have less lateral stiffness than their smaller predecessors. The wider spacing also enabled frame manufacturers to design bikes with shorter chainstays for more nimble handling and increased tire clearance for wider tires.
Super Boost: Pushing the Limits
Following the success of Boost, some manufacturers, particularly in the high-end enduro and gravity segments, sought further advantages. This led to the development of Super Boost, which features an even wider 157mm rear axle width. While a 157mm width was already common in downhill (DH) bikes, Super Boost differentiates itself by also moving the hub flanges outward, resulting in an even stronger and stiffer wheel build than Boost. This extra width provides more aggressive riders with improved durability and performance in the most demanding technical terrain. It also allows for a wider rear triangle and even greater tire clearance, accommodating the plus-size and fat tires favored by some riders.
Technical Comparison: Boost vs. Super Boost
The core differences between the two standards lie in their dimensions and their impact on wheel, frame, and drivetrain components. Here's a breakdown:
- Rear Axle Width: Boost uses a 148mm rear axle, while Super Boost extends this to 157mm.
- Hub Flange Spacing: The flanges on a Super Boost hub are spaced farther apart than on a Boost hub. This is the main contributor to the increased lateral stiffness of Super Boost wheels.
- Spoke Bracing Angle: The wider flange spacing on Super Boost hubs results in a flatter, more robust spoke bracing angle, which improves wheel strength and durability.
- Chainline: Boost typically uses a 52mm chainline, which is achieved by pushing the chainring out by 3mm. Super Boost, with its even wider rear spacing, pushes the cassette further outboard, resulting in a chainline between 55mm and 56.5mm. This requires a Super Boost-compatible crankset with a 0mm offset chainring.
- Tire Clearance: The wider architecture of Super Boost provides greater clearance for oversized tires, a key advantage for plus-size and aggressive trail bikes.
- Q-Factor and Heel Rub: While both standards maintain a similar Q-factor (the distance between the outer sides of the crank arms), the wider rear triangle of a Super Boost frame can increase the risk of heel rub for some riders.
Boost vs. Super Boost: A Side-by-Side Comparison
| Feature | Boost | Super Boost | Best For |
|---|---|---|---|
| Rear Hub Width | 148mm | 157mm | Boost: Standard Trail, XC, and Enduro bikes; Super Boost: Gravity, Aggressive Enduro, and Plus-Tire bikes |
| Wheel Stiffness | High | Very High | Boost: Excellent for modern MTBs; Super Boost: Maximizes wheel strength for the most demanding riding |
| Tire Clearance | Excellent | Even Greater | Boost: Ample clearance for most modern tire widths; Super Boost: Ideal for plus-size or fat tires |
| Chainline | 52mm | 55mm to 56.5mm | Boost: Standard for most modern drivetrains; Super Boost: Requires specific cranks and chainrings |
| Frame Geometry | Allows for shorter chainstays and increased stiffness | Pushes the geometry even further for strength and tire clearance | Boost: Versatile and widely compatible; Super Boost: Niche, high-performance applications |
| Compatibility | Broadly adopted and supported by most brands | Limited to specific high-end frames and component manufacturers like Pivot | Boost: The market standard; Super Boost: Requires careful component selection |
The Real-World Impact on Your Ride
For the average mountain biker, the decision between Boost and Super Boost will likely be made for them by the frame they choose. Most mid-to-high-end trail bikes currently use the Boost standard, which offers an excellent balance of stiffness, wheel strength, and compatibility. It provides all the modern advantages of wider hubs without sacrificing potential chainstay clearance or increasing the risk of heel rub.
Super Boost, on the other hand, is a more specialized standard. Its benefits are most noticeable in gravity-focused riding, such as aggressive enduro and downhill, where the absolute maximum wheel stiffness and durability are prioritized. It's also the go-to choice for plus-size and fat bikes that need the extra width for massive tires. Riders who demand the absolute peak of performance in these specific disciplines will appreciate the incremental gains offered by Super Boost. However, it requires a commitment to a less common standard, potentially limiting future component upgrades.
Ultimately, neither standard is inherently "better" than the other; they are simply designed for different purposes. Boost is the versatile, all-around champion, while Super Boost is the specialized athlete built for niche extremes. The choice depends on your riding style, the terrain you tackle, and your willingness to invest in a less common ecosystem of parts.
Conclusion
While both Boost and Super Boost represent the evolution of mountain bike standards aimed at improving performance, they cater to different segments of the market. Boost (148mm) has become the ubiquitous standard, providing a significant upgrade in wheel stiffness, tire clearance, and frame geometry for the vast majority of modern mountain bikes. Super Boost (157mm), an evolution of the concept, pushes these advantages to the extreme for aggressive gravity riders and those running plus-size tires. The key difference lies in the degree of width, which impacts wheel strength, clearance, and component compatibility. For most riders, Boost offers the ideal balance, while Super Boost is the specialized tool for niche applications, prioritizing maximum performance and durability above all else. A rider’s needs, terrain, and desired level of component compatibility should dictate their choice between these two hub standards. You can read more about mountain bike standards and their history on mountain bike specific sites like Pinkbike.
