Until the new fork arrived I had no idea what the heck is DH boost was. Yes, there is yet another standard. But did we really need another new hub standard — I mean, don’t we have enough?
It took a minute to wrap my head around this, so I figured I’d share my experience to save others the time.
It’s a bit confusing when you think about it. Boost spacing initially took the existing rear hub spacing of 142mm, and expanded it to 148mm rear spacing. Simple enough, and this helped frame designers and manufacturers increase clearance for the big rubber treads we’re all enjoying today. In the front, non-boost 15mm hubs were 100mm wide at the axle. The “boosted” increase expanded the axle width from 100 to 110mm, the same width as DH front hubs.
But that’s not all that changed. In the front the goal was a stiffer wheel, so the flanges of the hub were moved outward as well in order to reduce and eliminate wheel dish, thereby increasing lateral wheel stiffness. However, moving the flange outward also moved the location of the rotor mount outward from the traditional DH front hub spacing.
DH Boost Downhill Forks
I recently acquired a DVO Onyx DC-D1 DH fork. The DVO dual crown DH fork has 203mm/8″ of suspension travel (it also happens to be on sale at Jenson USA at the time of this post) and this fork looks quite trick. I was looking forward to getting it installed.. however, as I installed my front wheel, the brakes aren’t lining up with the rotor. It turns out, the new fork uses the 20x110mm DH Boost standard.
WTH? Fortunately for me, DVO includes a rotor spacing kit with the fork in the box. To make my front wheel (Spank 350 Vibrocore non-boost with 20mm adaptors) work with the new spacing, I simply removed my rotor and reattached it with the supplied 5mm rotor spacer and the longer bolts that were provided.
When did 20mm DH fork spacing change? And what the heck is this new spacing?
And what the heck has actually changed? Is the fork still 20 x 110mm? What the hell is 20mm BOOST? And why is there yet another hub standard? And do I need a different hub? Or does my hub now need adapters to make it work? So many questions.
Time to rely on my friend the Google and the assistance of the internet. Here’s the deal. DH boost is basically a boost front hub that uses a 20mm axle instead of a 15mm. Depending on the hub/wheel you have, this is a big deal, or just a minor inconvenience.
Depending on the wheel/ hub you’re running this change is fairly easy to adapt to. Fortunately, I’m running Spank wheels; all of the Spank Industries hubs are designed to be as future compatible as possible, with hub end cap adapters that can be swapped out to run any number of configurations. Converting a Spank front hub from 15mm to 20mm is as easy as swapping out the end caps, which are typically included with a wheelset.
Who makes Boost DH forks?
I can’t remember the last time I purchased an aftermarket DH fork. It was a big deal to acquire a new DH bike after a few years of not owning one, but now that I have one, I’m going to make sure this thing is dialed in, as I don’t plan to buy another one for a long time. Besides DVO, the newest iteration of the RockShox Boxxer, Fox 49 and Suntour Rux are now utilizing the updated spacing.
Either way, I’m unconcerned about the strength of my front wheel. How often do you really wreck a front wheel anyway? After bolting on the adapter and adjusting my brake, I was good to go and off to go ride my bike.