Mountain biking has seen significant advancements over the years, with many components evolving to enhance performance, durability, and compatibility. One such crucial component is the hub—the central part of a bike’s wheel that connects the spokes to the drivetrain and allows the wheel to spin freely. In this article, we explore the various hub standards and drivers commonly used in mountain biking, including Boost, Non-Boost, SuperBoost, Straight-Pull, and J-Bend hubs, as well as hub driver systems like the HG driver, XD driver, and Microspline driver.

 

Types of Mountain Bike Hub Standards

Non-Boost Hubs

Non-Boost hubs are the traditional standard that was widely used before the advent of newer, wider designs. The front hub width is typically 100mm, and the rear hub width is 135mm for quick-release setups or 142mm for thru-axle designs. While still used on many older or entry-level bikes, Non-Boost hubs have largely been phased out in favor of Boost and SuperBoost standards due to their limited support for modern wide tires and increased lateral stiffness.

Boost Hubs

Boost hubs were introduced to address the limitations of Non-Boost designs. Boost hubs increase the hub width by 10mm in the rear (148mm) and 6mm in the front (110mm). This wider stance allows for better spoke bracing angles, resulting in a stiffer wheel. The additional width also provides more clearance for wider tires and improved chainlines, making it a popular standard for modern trail, enduro, and cross-country bikes.

SuperBoost Hubs

SuperBoost hubs take the Boost standard a step further by increasing the rear hub width to 157mm while maintaining compatibility with standard Boost frame geometries. This design provides even more stiffness and allows for stronger, wider wheels without compromising drivetrain compatibility. SuperBoost hubs are commonly found on aggressive enduro and downhill bikes where strength and durability are paramount.

Straight-Pull Hubs

Straight-pull hubs use straight spokes instead of traditional J-shaped spokes. This design eliminates the weak point where the spoke bends, resulting in a stronger and lighter wheel. Straight-pull hubs are often used in high-performance mountain bike wheels where weight savings and durability are critical. They also allow for more uniform spoke tension, improving overall wheel performance.

J-Bend Hubs

J-bend hubs use spokes with a 90-degree bend at one end, which hooks into the hub flange. This is the most traditional spoke design and remains widely used due to its simplicity, availability, and ease of replacement. While J-bend hubs may not offer the same weight savings as straight-pull designs, they are often preferred for their compatibility with a broad range of wheel builds and cost-effectiveness.

 

Types of Hub Drivers

HG Driver (HyperGlide)

The HG driver, developed by Shimano, is one of the most common hub driver systems. It is compatible with Shimano’s 8- to 11-speed cassettes and is known for its reliability and widespread availability. The HG driver features splines that engage with the cassette, providing a secure fit. While functional and dependable, the HG driver is limited in its ability to support the smaller 10-tooth cog found on modern wide-range cassettes.

XD Driver

The XD driver, developed by SRAM, was designed to address the limitations of the HG system. The XD driver allows for the use of cassettes with a 10-tooth smallest cog, enabling a wider gear range. It achieves this by using a smaller and more refined freehub body. The XD driver is commonly used in SRAM’s 11- and 12-speed drivetrains, making it a popular choice for riders who prioritize high-performance gearing.

Microspline Driver

The Microspline driver, another innovation by Shimano, is specifically designed for 12-speed cassettes. Microspline addresses the limitations of the HG driver by allowing for a 10-tooth smallest cog while also reducing wear on the splines by using a greater number of smaller splines. Microspline drivers are increasingly found on modern mountain bikes equipped with Shimano’s 12-speed drivetrains and offer excellent compatibility and performance.

 

 

 

Comparison of Hub Standards and Drivers

 

Feature	Non-Boost	Boost	SuperBoost	Straight-Pull	J-Bend
Front Hub Width	100mm	110mm	110mm	Varies	Varies
Rear Hub Width	135/142mm	148mm	157mm	Varies	Varies
Stiffness	Moderate	High	Very High	High	Moderate
Weight	Moderate	Moderate	Slightly Higher	Lightweight	Moderate
Ease of Repair	High	High	Moderate	Moderate	Very High

Driver System	HG Driver	XD Driver	Microspline Driver
Smallest Cog	11-tooth	10-tooth	10-tooth
Compatibility	Shimano 8-11	SRAM 11-12	Shimano 12-speed
Spline Design	Large splines	Small splines	Micro splines
Common Use	Entry/Mid-tier	High-end	Modern Shimano systems

To Sum It Up

Understanding the various hub standards and driver systems is essential for selecting the right components for your mountain bike. Whether you prioritize stiffness, weight savings, or gearing performance, there is a hub and driver combination tailored to your needs. As technology continues to evolve, these standards and systems will likely further adapt to meet the demands of modern mountain biking, ensuring that riders can tackle any trail with confidence.