Trek's 148 Boost Rear-Axle Standard
How is it that we love new stuff, but hate change? We're continuously asking more out of our bikes: Get lighter, be stiffer, go uphill better, go downhill better–and then we scoff when something changes what we're used to or adds yet another 'standard' to the ever-growing pile of standards. It's because we're skeptics. The bike industry has trained us to be weary of 'advancements.' For every step forward, like thread less headsets, we seem to have a step backward, like Dual Control shifters. Our skepticism is a checks and balances system. Good things stick around, bad things don't. Is Boost 148 a good thing?
When Trek told us about its 148-millimeter rear-axle spacing, our first reaction was to turn our noses up. We just figured the whole axle spacing thing out, didn't we? But Trek swore that it was legit, so we flew out to Waterloo to get the story on Boost 148, and see if this was just a marketing gimmick or the real thing. Check out our exclusive video below and then read on for a bit more explanation.
If you boil it down, this is sort of what's going on. When bikes went from 135-millimeter spacing to 142, the hub flanges didn't actually widen to make a stiffer, stronger wheel. Stiffness was gained in the frame by replacing a quick release with larger diameter thru-axle. The 142 is nice because you can turn a 135-millimeter hub into a 142 just by swapping end caps, but it's only part of the equation. We made things wider, but didn't utilize the extra real estate to make a better wheel. Boost 148 is meant to address this. Trek feels that the bike segment that can benefit the most from this is long-travel 29ers, so Boost 148 is debuting on the Remedy 29.
Why 148 millimeters? That sounds like an arbitrary number. Trek engineers found that this was about as wide as they could go without affecting the Q-factor on current cranks. Boost 148 does require a different crank (or in the case of SRAM, just a spider) than a 142-millimeter spaced bike to correct the chain line, but overall crank width stays the same. The added bracing angle achieved by widening the hub flanges within these constraints creates a 29-inch wheel that tests as stiff and strong as a 650b wheel.
Why not use the 150 spacing used on DH bikes? It sounds close, but the 150 standard used on downhill bikes is actually 157 millimeters wide, and requires wider crank spacing.
What about carbon rims? Aren't they stiff enough? Sure, high-end 29ers with ultra-expensive carbon hoops are wicked stiff, but they're too pricey for most people to experience the benefit. Boost 148 is about engineering strength and stiffness into the design rather than relying on advanced materials to get the job done. The SRAM Roam 40 wheels on the pre-production test bike that we've been riding retail for about $375 and they're impressively stiff.
Speaking of SRAM... Since Trek's expertise is making frames, not drivetrains, Trek went to SRAM to help develop Boost 148 as system to make sure that shifting quality wasn't sacrificed. This is why you don't see Bontrager wheels on these first Boost-equipped models. Boost 148 is not a closed standard. If other brands see the benefit, they'll be free to utilize it.
We came into this thing as skeptics, but after talking with the guys at Trek and riding Boost 148 for ourselves, we think it's a damn good idea. Ultimately, though, it'll be you who'll decide weather this thing lives or dies.
