In the ever-evolving realm of the bicycle industry, where compatibility seems to be a perpetual puzzle, there emerge two distinct breeds of 20mm through axle systems: the 20x110mm and the 20x110mm Boost. Yes, you read that correctly. But fret not, for we're here to shed light on this perplexing subject.
Does this pertain to my biking world?
For those on XC and Trail bikes, this matter is a non-issue. If your trusty two-wheeler utilizes a 15mm axle (which is the norm outside of hardcore downhill rigs), you can simply return to the Worldwide Cyclery YouTube video marathon – nothing to concern yourself with here. However, if you currently possess or plan to acquire a DH fork or a robust single-crown fork equipped with a 20mm through axle, or perhaps a wheelset tailored for such a fork, the following minutes of reading could save you both heartache and exorbitant return shipping expenses.
Around mid 2018, a multitude of fork manufacturers had begun relocating their disc brake mounts outward, thereby rendering their forks compatible with "20x110mm Boost" hubs. It's vital to note that the overall spacing between the fork legs remains at 110mm, and the axle diameter remains steadfast at 20mm. So, what exactly does "Boost" signify in this context? The disparity lies in the placement of the disc brake rotor and the width of the hub's flanges – the points where the spokes attach to the hub. Despite both hubs boasting a 110mm width, the Boost version features hub flanges that have been shifted 5mm outward on each side, which consequently nudges the disc mount closer to the fork. A visual representation of this discrepancy can be found in the accompanying photo.
The primary objective behind widening the hub flanges is to optimize the bracing angle for your spokes, thereby crafting a more robust wheel. These broader hub flanges necessitate shorter end caps and a wholly different hub shell with wider flanges and an altered disc brake mount location. Consequently, a traditional 20x110mm (non-Boost) hub cannot be genuinely converted into a 20x110mm Boost hub with a simple end cap swap.
Photo: Stan's No Tubes
But wait, can't I merely insert a spacer behind my rotor to convert any 20x110 hub into a 20x110mm Boost-compatible fork?
In a technical sense, yes, it's possible. However, this approach forfeits the advantages of wider flanges and a sturdier wheel, and it may entail a few disadvantages as well. Since add-on components like rotor spacers often imply decreased strength, our recommendation leans toward opting for a dedicated 20x110mm Boost hub when interfacing with 20x110mm Boost forks.
Photo: Fox Racing
I'm buying stuff and I'm not sure what I have. What's the worst-case scenario here?
The most unfavorable outcome would entail unintentionally purchasing a brand-new 20x110mm Boost wheel and subsequently realizing it's incompatible with your standard 20x110mm (non-Boost) fork. If you're in the market for a DH fork, or especially a wheelset, invest the extra effort to ascertain the specific 20x110mm front hub requirements of your fork. Currently, prominent forks such as the RockShox BoXXer, Fox 40, DVO Onyx, have adopted the 20x110mm Boost spacing. When in doubt, reach out to us and we can help. If you already possess a fork and are searching for the ideal wheelset, rest assured that we can help you find the correct hub and/or wheel for your DH fork.
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