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A Future-Proof Boost Hub

The Ask: A "Boost" spaced hub for 20mm thru axles.

In February of 2017 the Santa Cruz Syndicate came to us with a request. Greg Minnaar raced his Santa Cruz Hightower at the Enduro World Series in Finale Ligure, Italy in late 2016 and saw the potential of a 29” wheels in downhill.

Developing a world cup downhill bike is not as simple as Santa Cruz making a new swingarm. The new bike would require a new fork, new rims, new tires, new hubs, and custom headsets. While Santa Cruz set to work developing a 29er V10, Fox stepped in to design a new Fox 40 for the 29” wheeled downhill bike. The final version of the new Fox 40 features “Boost” disc spacing which meant a standard 20x110mm DH hub would not fit.


Minnaar on the Hightower


The new disc mount location of 20x110 "Boost" allowed us to completely redesign our large diameter bearing front hub. The result is the ISO AB, with a wider flange location, and a highly sculpted and optimized hubshell. The new ISO AB hub is compatible with all forms of "Boost" axles, 110x15, 110x15 with Torque Caps, and 110x20 with “Boost” spacing!

ISO AB hubs built to ENVE rims



To tackle the immense loads of downhill and enduro racing the ISO AB uses our large diameter hub bearings that will distribute abuse over 24 ball bearings on our made-in-house angular contact bearings, compared to most hubs on the market that have just 9 ball bearings on radial races. Our bearings are specifically designed for bikes with adjustable preload, so they wear in not out, getting faster with every ride.

Development and Testing:

We tested this new design through our Buzzworks development program with the Santa Cruz Syndicate. They raced the hub throughout the 2017 Downhill World Cup series taking five podium finishes! While the prototype, buzzworks ISO AB hub was proving itself on the world stage we were busy bolting forks into our testing fixtures and laying on the abuse, testing different axle designs, making minute adjustments to the design and testing again. Our engineering resilience drives us to iterate and refine until we rest on the absolute best design to tackle the presented problems.

Chris King bearings are engineered to be easily user serviceable, we use low friction seals and reusable snaprings. With a quick and simple service our bearings will far outlast your bike and roll fast and smooth their entire life.


Greg Minnaar

Greg Minnaar riding the ISO AB prototype.

Which hub is right for me?


With this new design you may be asking how to choose between our two mountain bike front hubs, the ISO B and the ISO AB. Here are a few of the differences to consider.

Our ISO B front hub is designed to be lightweight and fit a wide variety of front axle standards. The ISO B can fit QR, 100x15mm, and 110x15mm "Boost" axles. It uses our small diameter hub bearings to save weight but it is extremely durable, ready for anything from enduro to gravel. The ISO B also comes in a lower 24 hole count drilling to pair with many modern carbon mountain bike rims, such as the ENVE M525.

The new ISO AB is specifically for “Boost” disc spacing forks with 110x15mm "Boost" or 110x20mm "Boost" axles. Using the larger diameter hubshell bearing the ISO AB is designed to tackle rough terrain and aggressive riding such as downhill and enduro. In an evolving landscape of axle specifications, we are confident that the “Boost” disc location is here to stay. With the ISO AB hub your wheel will be future proof and ready to convert to the new 110x20mm axle with a simple insert swap, should that spec expand beyond downhill forks in the coming years.

Click here to see complete wheel building specifications for all of our hubs.

Whichever Chris King hub you choose, know that you are riding the best bearings available, which we have perfected over the last 40 years of engineering bicycle bearings.

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