The Shift from Standard to Boost
Before Boost, the standard rear axle spacing for mountain bikes was 142mm. However, as wheel sizes grew from 26 inches to larger 27.5 and 29-inch options in the early 2010s, manufacturers needed a way to counteract the corresponding decrease in wheel stiffness. The solution was to create a wider hub standard.
What is Boost Spacing?
Boost is the hub spacing standard with a 148mm rear axle and a 110mm front axle. The extra width pushes the hub flanges—the parts where the spokes attach—further apart. This wider bracing angle creates a stronger, stiffer wheel, which is a significant advantage for larger wheel sizes.
**Key Features of Boost:
- Rear Axle: 148mm
- Front Axle: 110mm
- Chainline: 52mm, requiring Boost-specific cranks and chainrings
- Wheel Stiffness: Improved lateral stiffness compared to the older 142mm standard
- Frame Compatibility: Allows for shorter chainstays and increased tire clearance
The Benefits of Boost
The move to Boost spacing offered a range of performance improvements for mountain bikes, which is why it became the industry standard so quickly. Wider hub flanges result in stronger, more durable wheels that can withstand rougher terrain and aggressive riding. The design also enabled manufacturers to build frames with shorter chainstays for more nimble handling, while still accommodating wider tires for better traction.
The Evolution to Super Boost
Not long after Boost was adopted, some manufacturers pushed the limits further, seeking even more stiffness and tire clearance, particularly for enduro and gravity-focused bikes. This led to the creation of the Super Boost standard.
What is Super Boost Spacing?
Super Boost, also known as Super Boost Plus (SB+), uses a 157mm rear axle spacing. This standard was borrowed from the downhill (DH) segment, which has used 157mm rear axles for some time. The critical difference lies in the flange placement. While DH hubs at 157mm often used a standard flange width, Super Boost hubs utilize a wider flange spacing, resulting in an even stiffer wheel than Boost.
**Key Features of Super Boost:
- Rear Axle: 157mm
- Front Axle: 110mm (same as Boost)
- Chainline: Approximately 56-56.5mm, requiring Super Boost-specific cranks and chainrings
- Wheel Stiffness: The widest spoke bracing angle available for trail bikes, leading to the highest lateral wheel stiffness
- Frame Compatibility: Specifically designed for frames requiring maximum tire clearance and stiffness, with wider chainstays
Who is Super Boost For?
Super Boost is not for every rider. It is typically found on high-end, long-travel enduro, and gravity mountain bikes designed for aggressive descents and high-impact riding. The additional stiffness and durability are most beneficial when tackling extremely technical and demanding terrain where wheel deflection is a concern. Riders who frequently use plus-sized or fat tires will also benefit from the increased clearance.
Boost vs. Super Boost: A Comprehensive Comparison
| Feature | Boost (148) | Super Boost (157) |
|---|---|---|
| Rear Axle Width | 148mm | 157mm |
| Front Axle Width | 110mm | 110mm |
| Wheel Stiffness | High | Highest |
| Spoke Bracing Angle | Wide | Wider |
| Tire Clearance | Good, suitable for most plus-sized tires | Maximum, ideal for aggressive or plus-sized tires |
| Chainline | 52mm | 56-56.5mm |
| Crank Compatibility | Requires Boost-specific cranks | Requires Super Boost-specific cranks |
| Frame Type | Standard for most modern trail, all-mountain, and enduro bikes | Niche standard for high-end, gravity, and aggressive trail bikes |
| Heel Rub Potential | Less likely | Higher potential due to wider chainstays, if frame is not well-designed |
Compatibility Considerations
The most important takeaway is that Boost and Super Boost components are not directly interchangeable. You cannot fit a Super Boost hub into a Boost frame, nor can you use Boost cranks on a Super Boost frame without the wrong chainline. This is a critical factor when purchasing new components or upgrading your bike. The need for a specific frame, hubs, and cranks means that adopting a different standard requires a significant investment in a new ecosystem of parts.
Which Standard is Right for You?
- Choose Boost if: You're building or buying a modern trail, all-mountain, or enduro bike. It's the industry standard, widely supported, and offers a proven balance of stiffness, handling, and clearance for most riders. For the vast majority of mountain bikers, Boost is more than sufficient.
- Consider Super Boost if: You are an aggressive, gravity-focused rider who values maximum wheel stiffness and durability above all else. This standard is for those pushing the limits on the most technical terrain or who require extra clearance for specific plus-sized tire setups. It's a performance-first choice with some potential compatibility tradeoffs.
Conclusion: Choosing Between Boost and Super Boost
The central difference between Boost and Super Boost comes down to their rear axle spacing—148mm versus 157mm, respectively. This seemingly small measurement has a domino effect on the entire bike's architecture, influencing wheel stiffness, tire clearance, chainline, and frame design. While Boost offers a performance-optimized setup that has become the modern standard for good reason, Super Boost takes that formula to the extreme, prioritizing maximum strength and durability for the most aggressive riding conditions. The choice ultimately depends on your riding style, component needs, and the specific demands of the terrain you ride. For most riders, Boost provides the perfect balance of performance and compatibility, while Super Boost caters to a niche of gravity enthusiasts seeking the ultimate in wheel rigidity. For a detailed guide on specific component choices, visit a reputable component manufacturer's blog, such as the Race Face crank selection guide.
