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If last week's 27.5 PLUS announcement from FOX left us wondering how serious this introduction of a new set of hub standards really was, the fact that SRAM is now following suit is a clear indication that we're looking at more than a fad. SRAM call it "BOOST", which to simplify greatly translates to 148x12-mm rear hubs, and 110x15-mm front hubs (with matching chainline changes in the rear). But in contrast to FOX's launch of a 27.5 PLUS fork, SRAM are taking the basic concept much further, and they are doing so without making it 27.5 PLUS-specific.

What Is Boost And Why Is It Being Introduced?

SRAM say that the bigger wheels we see on today's bikes as well as the capabilities of the modern breed of all-mountain or enduro bikes all place a lot more stress on wheels, and that a wider hub will help to build stronger wheels without taking on extra weight. Additionally, frame designers are constantly looking at ways to gain space around the bottom bracket/chainstay area, and although 1x-specific frames are a step in the right direction, SRAM say that they have been looking at ways to move the chainline further outboard as well for some time. It took until a bike manufacturer (Trek) was ready to take a new standard to market for it all to gain proper momentum, to the point where SRAM are now releasing an open wheel and drivetrain specification and a host of ready-to-roll components applying it.

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Boost Cranks And Rear Hubs

Starting at the crank, Boost moves the chainline 3-mm outwards without affecting the Q-factor. In other words, the chain ring moves outwards, but not the crank arms. This move frees up space around the crankset (making it easier to design shorter chainstays, wider suspension pivots, and to improve tire clearance). Additionally, it modifies the chainline to correspond to the new, wider rear hub spacing.

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In regards to the hub, as previously stated the main goal is to create a wider flange spacing to help build stronger wheels. SRAM claim that given the same rim and spoke spec, a 29" Boost wheel will have the same stiffness as a 27.5" wheel built on a classic 142-mm hub. Note that the new standard is designed to work as a system, so you won't be able to mix and match between Boost and non-Boost drivetrain components (because of chainline compatibility issues).

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Boost Forks And Front Hubs

Just as on the new FOX 34 27.5 PLUS fork launched last week, SRAM are introducing a wider front hub as part of their Boost standard - taking it from the classic 100x15-mm to 110x15-mm. It's not just the axle that grows longer, hub flanges and brake disc mounts are all moved out by 5-mm on each side, creating the wider spoke bracing angle sought to help improve wheel stiffness. In contrast to FOX however, SRAM are not making forks specifically for 27.5 PLUS, in fact you have to resort to running a 29" Boost fork to fit a 27.5 PLUS tire, SRAM say. At this point, it seems as though SRAM wants the new standard to deliver stiffness benefits across the range of "normal"-sized tires, and that they are not willing to create an extra wide fork to accommodate 27.5 PLUS specifically. Of course, SRAM already have a proper fat bike fork in the Bluto, so maybe they feel less urgency around 27.5+ in general.

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To summarize this introduction, here are the benefits that SRAM sought to help deliver with the Boost standard:

  • Increased wheel stiffness and durability
  • Better riding efficiency and bike handling precision
  • Improved frame geometry with shorter chain stays
  • Wider and stiffer suspension pivots
  • Wider range of chainring options
  • More clearance for bigger tires

A new standard is all good and well, but what about actual components that apply them? SRAM are introducing new cranks, hubs, wheels, and forks to support this new standard, and it's fair to assume we'll be seeing them appear on new bikes shortly - SRAM wouldn't put in this amount of work unless it had potential clients lined up, beyond Trek.

Cranks

Two cranks are available with the new Boost option, XX1 and X1 1400.

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XX1 Crank Highlights

  • X-SYNC™ tooth profile provides maximum chain control
  • Carbon arms with forged aluminum spider
  • CNC- X-SYNC™ Direct Mount ring
  • BOOST option
  • Wide/narrow Q-factor cranks for BB30 and GXP

X1 1400 Crank Highlights

  • X-SYNC™ tooth profile provides maximum chain control
  • Hollow forged aluminum arms with forged aluminum spider
  • Chain ring guard option
  • BOOST option
  • CNC - X-SYNC™ machined ring

Hubs

Two hubs with Boost option are available, X0 and MTH 700.

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X0 Hub Highlights

  • Tapered aluminum axle is stronger without added weight
  • All axles types
  • 32 spoke holes
  • BOOST 12x148 and 15x110 options
  • Sand-blasted black with red label
  • Glossy black with silver accents
  • 11-speed XD™ Driver Body
  • 10-, 9- and 8-speed driver body
  • Weight: 130g (front), 250g (rear)

MTH 700 Hub Highlights

  • 32 spoke holes
  • BOOST 12x148 and 15x110 options
  • Black
  • 11-speed XD™ Driver Body
  • 10-, 9- and 8-speed driver body
  • Weight: 170-410g

Wheels

SRAM are making one Boost compatible wheelset available now - note that it is not rated for "ENDURO" use according to SRAM, so if you're after a harder hitting option, you'll need to have a wheel built on one of the new hubs (or look out for other wheel manufacturers jumping on the Boost train).

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ROAM 40 Wheel Highlights

  • Lightweight aluminum rim with asymmetrical TAPER CORE™ profile—with a welded joint
  • UST tubeless
  • User-friendly SOLO SPOKE™ technology
  • Durable, precision-machined SPEEDBALL™ bearings
  • Strong, fast engagement with DOUBLE TIME™ hubs
  • Available in all three wheel sizes
  • BOOST 12x148 and 15x110 options available for 27.5" and 29"
  • Convertible to any axle type
  • Available in XD™ or 10-speed driver body
  • Color: Black/Silver

Forks

To support the new front hub standard, Rockshox are adding Boost options to its most popular forks - the SID, Reba, and of course the Pike. Of note are also the updates to the graphics packages for 2016.

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Model Year 2016 Rockshox Fork Highlights

  • 110x15mm hub spacing option availablefor MY16 SID, Reba, Pike.
  • All 29” forks with Boost compatibility alsofit 27.5” Plus wheels (27.5” x 3.0 tires)
  • Torque Cap Compatible: Larger interface between dropout and hub end cap results in stiffer frontend – increased steering precision, better bike handling, more confidence.All RockShox 110x15mm forks are Torque Cap compatible.
  • Availability:
  • SID 29” Boost/27.5” Plus and Reba 29” Boost/27.5” Plus : June 2015
  • Pike 27.5” Boost and 29” Boost/27.5” Plus: Summer 2015

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Boost Product Overview and Pricing

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More information on www.SRAM.com.

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