Three years ago Giant Bicycles made big waves when they boldly declared that both 29” and 26” would be replaced as wheel standards for mountainbikes by 27.5”, a standard originally known as 650B. For the 2014 model year they rolled out 27.5” versions of their XC machines, the XTC hardtail and full-suspension Anthem. Of course, whenever the bike industry declares a “new revolution in design” is in progress, it’s always fun to check up on the prediction later (often to be enjoyed with a fine glass of schadenfreude). Now that a three-year product cycle has elapsed, haters might be eager to point out that Giant has backtracked on phasing out 29er”. Yet at the same time, it would be difficult to claim that 27.5” has failed, since the new Anthem and XTC bikes are being marketed as +/29”, meaning that in addition to the typical 29” wheels with 2.0-2.25” wide tyres the frames also can fit 27.5” plus that is, 27.5” wheels with tyres in the wide (but not fatbike wide) 2.8-3.2” range. The idea is that the 29er wheels give the bike a fast XC character while the 27.5”+ give surer grip and gusto in rougher trails conditions while avoiding the heavy wheels and long wheelbase of required of 29 x 3.0” tyres.
This dual wheel concept is the natural byproduct of the decade-long trend towards wider tyres in all virtually all categories of bicycles, facilitated by hub-mounted disc brakes and to a lesser extent new, wider axle/hub standards. Since it is no longer a braking surface, the wheel’s rim diameter is less relevant than the tyre’s overall diameter. A 27.5”+ tyre fits a rim with a 584mm bead set diameter but has an outside dimension approaching that of a 29 x 2.1” on a 622mm rim. That’s a lot of tyre to squeeze between fork blades and chain stays, so many manufacturer’s are taking up the new “Boost” standard for thru-axle hubs, which adds 10mm to front hubs and 6mm to rear hubs. With the cassette pushes further outboard, optimum chainline also moves away from the centerline of the frame, though the distance between the pedals, commonly known as Q-factor, is not necessarily affected.
All these changes have added to the already bewildering number of sku#s for MTB cranksets and hubs (especially if you add in the product catering to fatbikes). Just to point out one more aspect of this trend, the popularity of plus-sized tyres is prompting rim manufacturers to offer wider options. Arguably this is more important for 27.5”+/29er dual wheel concept than for the separate 29er+ niche. Whereas the latter simply seeks to add a bigger footprint to a 29er wheel, the 27.5”+ tyre needs to provide the wider footprint as wheel as closely approximate the overall diameter of a 29 x 2.2” tyre so that the wheels are interchangeable without changing the effective gearing, bottom bracket height, and handling. Thus a 27.5”+ tyre suited for a dual wheel bike like those in Giant’s new lineup may have an especially tall sidewall, that would otherwise collapse under hard cornering if not supported at the bead by a wider rim. Suitable rims have internal widths upwards of 40-45mm, far bigger than the ~21mm that was common up until 2000, or even the 25-30mm of more recent times. Just to complicate things, not all 27.5”+ tyres are being marketed to the 27.5”+/29er dual concept, so some are just short and wide.
The dual wheel setup of the new 2017 Giant MTB lineup has a parallel in the 3T Exploro that Head Bike Hugger Byron is reviewing right now. The Exploro uses the same two rim standard (ISO-584mm and ISO-622mm) but with comparatively skinnier tyres and more pointedly, dropbars. The Exploro is designed to fit 40mm tyres on 700C wheels (to put that in MTB terms, 29 x 1.6”) or 2.25” tyres on 650B (ie 27.5”). Thankfully, the 3T takes conventional compact road cranks and 100x15mm/142x12mm thru-axles, and 650B x 2.25” tyre doesn’t need particularly tall sidewalls to get to the size of a 700C x 40mm.
The mind blown part of this bike story…. The EXPLORO is basically a Tarmac (a benchmark for road disc) with a few mm in the wheelbase, a half degree in the head tube; and double the tire clearance while offering an aero benefit, and lower weight.
It’ll roll with 650bs or 700cs too.
The keg on the top tube is because I’m all in for road bikes on dirt, but #nobento. No matter the aero benefits.
I was going to write a thoughtful analysis of the Olympic road races, but then the EXPLORO showed up, demanding all my attention, and ride time.
A lovely edit from OZ Trails, and a quick video escape on a Monday….
Joey Schusler and Rosara Joseph didn’t know what to expect when they planned their visit to the Ozark mountains. Shortly after take off it became crystal clear they were about to experience a backcountry mountain bike adventure of a lifetime. Cessna’s and Piper Cubs, the Upper Buffalo wilderness and a beautiful network of IMBA Epic trails. Join Joey and Rosara as they discover what locals have known for years… Do you know Northwest Arkansas?
This just arrived, tires from WTB for the OPEN Cycle U.P. with all the details to follow. Read about the U.P, number 17, in the latest issue of our magazine on iTunes, Apple News, the web, and Medium Bicycles.
Whatever the marketing nomenclature, road bikes on dirt are fun. This is a Vine of the Open Cycles U.P. we’ve got in on demo. It’s also the focus of an article in issue 38 of our magazine, dropping very soon. GravelPlus is a gravel grinder that can run 650b to 700c tires. Here’s how Andy Kessler and Gerard Vroomen define it.
Andy and I are very excited to introduce the U.P. (Unbeaten Path) today. It is our new GravelPlus frame, a gravel grinder without limits. Ideal to go off the beaten path, from exploring a few gravel or dirt paths during your local ride to taking “the road never traveled”.
For me personally, this is probably my favorite frame ever, because it best reflects how I most like to ride. Asphalt is great to get you to the places where the real fun happens, and that is on gravel and dirt, away from cars and other fun-crushing obstacles. Over the past years, it’s been hard to miss that many people feel this way, witnessing the emergence of gravel rides and other adventurous styles of riding. So we hope the U.P. will be as exciting for you as it is for us, and if not, at least I’ve got my favorite bike now!
U.P.’s geometry is performance-oriented, so closer to a cross/road position than a mountain bike position. Combined with clearance to fit mountain bike and road/cross cranks, this gives you a comfortable and efficient position to far and fast on any terrain.
U.P. also fits the widest range of tires – even mountain bike tires – so not even the toughest conditions can stop you. We’ve placed a great emphasis on compatibility for U.P. The rear axle is 142×12 thru-axle so you can fit your 29er and 650b mountain bike wheels. The BB standard is BB386 EVO so you can fit virtually any crank you desire (rather important since the frame is meant to accept both mountain and cross/road cranks). Headset, seatpost, everywhere we’ve gone with the most common standards as long as they made sense.
When running 650bs and 2.1 tires on, I call it a dropbar mountain bike, or pretty much what Tomac was racing, back in the day. The U.P and the 3T Exploro are where the innovation is in the bike industry; the equivalent, of say what Aero road was 5 years ago. You know, when Gerard was at Cervelo.
The OPEN U.P just arrived, and it’s like Christmas in July; at least for those of us into riding road bikes on dirt. Away from the pavement is another type of riding: acute, contrasting, and with scenery like I shared yesterday on Medium. The U.P is one of the adventure bikes I’m riding late summer and into the fall. I hope past another beaver dam.
On a suffering scale of 1 to 5, with 5 being “on the phone calling for help,” this ride was a 2. What hitting level 2 did do, is remind us of past 5s, and we knew how to get back to the car safely. This summer we’ve been riding every inch of the Iron Horse Trail and making our way, trailhead by trailhead, towards Ellensburg. We’ve ridden through 3 of the 4 tunnels on the State’s rails-to-trails park.
Read the the rest of the story about our Iron Horse trail rides on Medium Bicycles, and in the next issue of our magazine when it drops later this week. I had a Scott Addict CX-1 with me.