The first hint
that a new hub spacing standard was on the way occurred early last summer when Trek
released the details of their new Remedy. The bike had 12x148mm rear spacing, a development that came about through a collaboration with SRAM and given the name Boost 148. But despite the fact that Trek was the first company to roll out bikes with Boost 148, this isn't a proprietary design. Instead, it's an open standard that can be used by any bike manufacturer, and by the looks of things, a number of companies will be hopping on board in the very near future.
To go along with the Boost 148 rear, SRAM has now officially announced Boost 110, which uses a 15x110mm thru axle (as opposed to the current 15x100mm spacing). Like Boost 148, which moves the rear hub flanges 3mm outboard on each side in order to improve the spoke bracing angle and increase wheel stiffness, Boost 110 moves the front hub flanges out by 5mm on each side to accomplish this same goal for the front wheel.
Going to a hub with 110mm spacing also means that fork legs need to be widened slightly, a move that has the added benefit of
increasing tire clearance. This means that a 29” Boost 110 fork will also work with 27.5+ wheels, which use a 27.5 x 3.0” tire. Confused yet? Hopefully not, but it is a lot to digest, especially when you add in the fact that Boost 148 requires a slight drivetrain change, in the form of a chainring spider that's offset by three millimeters to accompany change in cassette position. To help clarify things, here are the Boost basics in list form:
Boost 110• 15x110 front hub spacing
• Hub flanges move outboard by 5mm
• The increased distance between fork legs lets 29” Boost forks work with 27.5 x 3.0” tires
• A 29” wheel built with a 15x110 Boost hub is claimed to be as stiff as a 26" wheel built with a standard 15x100 hub.
Boost 148• 12x148mm rear spacing
• Hub flanges move outboard by 3mm
• Improved bracing angle is claimed to put the stiffness of a 29” wheel on par with that of a 27.5” wheel on a 142mm hub.
• Requires chainline to be adjusted 3mm outboard via a different chainring spider. This does not affect the crank's Q factor.
SRAM's Boost Components
Since SRAM is the driving force behind the Boost standard, it's not surprising that they have a growing line of components to go along with it. Boost versions of their Roam 40 wheelset will be offered in 27.5” and 29” options, and there will also be Boost X0 hubs. There is also a MTH 700 Boost hub, which uses the same internals as SRAM's X9 hubs.
Regarding suspension forks, Boost 110 version of the RockShox SID and Reba will be released this June that will work with 29” or 27.5+ wheels, and later in the summer two different Boost versions of the Pike will be available, one for 27.5” wheels, and one for 29” or 27.5+ wheels.
End Cap Swaps?
The short answer to the question, “Can't I just swap out my hub end caps in order to use my existing wheels on a frame designed for Boost 148?” is 'No.' This is due to the widening of the hub flange width. Hub axle end cap swaps were possible with 15x100 or 12x142mm spacing because the actual hub width didn't change with either of those standard – both were based off of the existing quick release hub dimensions. With Boost, the hubs are actually wider, which moves the position of the disc brake rotor further outboard as well. Granted, armed with a handful of spacers it may be possible to rig something up, but taking the MacGyver route has the potential for severely compromising strength, whether that's at the disc rotor or the axle, and neither is a good spot for failure.
Changes are certainly afoot in the mountain bike industry, but there's still something missing. All of these Boost components need somewhere to go, and except for Trek, no other major player has released a Boost 148 bike, and no large manufacturer has announced a production 27.5+ bike. Boost 148 allows for more tire clearance, and also creates room for wider suspension pivots, shorter chainstays, and additional room for a front chain ring, all of which have been limiting factors for bicycle frame design in the past. There's no doubt that bikes that take advantage of the new standard will be revealed in the near future – the fact that both SRAM and FOX have announced Boost 110 forks is a clear sign the accompanying bikes are on the way. The Taipei Cycle Show takes place this week, followed by Crankworx Rotorura and then the Sea Otter Classic soon after, all of which are likely places for the next generation of mountain bikes to start appearing. Pinkbike's Take:
|Whenever a new standard is introduced, a certain amount of resistance is to be expected. After all, who wants to find out that the bike that they purchased last week already has technology on it that's no longer the latest and greatest? Look back in the archives to 2008 when the 15x100 thru axle was introduced, or 2011 when 12x142 came about and you'll see the same arguments against change as there are today. At the same time, if the industry didn't move forward (granted, it does sometimes go sideways, and even backwards), we'd still be riding with cantilever brakes and toe clips. Wider tires and stiffer wheels combined with the frame design potential that Boost allows certainly sound like good things, but plenty of questions still remain, and until we have actual trail time on these new products the jury is still out, although by all indications Boost is here to stay... at least until the next new standard pops up a few years down the line. - Mike Kazimer|