A Bit About Wheels
Collectively, the mountain bike industry isn't huge on the idea of change. It creeps and crawls along, working its way into our hardware at just such a pace so as not to frighten us away. This is why the hot topic of late is wheel size. Unlike the addition of more cogs into our transmissions, rigid frame spars being replaced by shocks and pivots or fluid powered brake calipers squeezing a rotor, wheel size is a lot more in your face.
After years of acceptance, the 26" wheel was suddenly thrust into battle with what many considered an advantageous 29" hoop. Like always, there was immediate resistance followed by compromise. Initially designers tried to mix and match the strengths of the two different wheel sizes by literally mixing and matching the two different wheel sizes. 96ers (29" in the front, 26" in the rear) and 69ers came into being in the hopes of capitalizing on each of the two wheel size benefits while minimizing the disadvantages. Some models worked pretty well, others not so much.
This all brings us to the latest in wheel revolutions: the 650B, which measures in at roughly 27.5" or halfway between the 26 and 29" wheel. Momentum on the 650B movement has been understandably slow considering many insist there simply isn't room in the market for three different sized tires; a fact especially relevant when you stop to consider that the new wheel size itself is only the beginning. Tires, forks, brakes, bearings, even frame geometry itself all have to be built around the diameter of the wheel. These days more and more aftermarket companies have decided to join the fray and that brings us to the Dakar Sixfifty B Comp from Jamis- the first bike to enter our test shop from a factory spec'ing 650B hoops.
Taking a look around the Dakar Comp reveals a pretty decent spec/dollar relationship even if you couldn't care less about the size of its wheels. Bringing the squish is an X-Fusion Velvet RL 650B-specific fork good for 5.1" of travel and a RockShox Monarch R air shock (also 5.1" of travel) in the rear. The 30-speed transmission (10x3) is made up mostly of Shimano SLX bits (exception: SLR Rapidfire Plus shifters). Braking comes from Avid's Elixir 3 hydraulic discs front & rear. Those 650B wheels come in the form of WTB LaserDisc Trail rims & hubs wrapped in Kenda Nevegal rubber. Odds and ends include Shimano M552 Hollowtech cranks, a Ritchey Mountain Riser bar, Ritchey stem and WTB Volt saddle.
All told our size medium test sled weighed in at 33-pounds and one can be had identical to ours for $2679
We must have been spoiled around here by testing a rash of hardtails these past few months because when we first took a look at the Jamis Dakar, we had a tinge setup anxiety. Not to worry though, taking a little time to dial in the bike's suspension is time well spent. The X-Fusion fork in particular can appear a bit intimidating to those of us used to Fox, Marzocchi or so on but the fact of the matter is that there's nothing abnormal here. Pump the fork's air spring up to about an inch of free sag based on the manufacturer's weight chart and fool around with the rebound adjuster until you find your own personal sweet spot based entirely on feel.
The shock is simpler still with easy to read sag gradients printed right on the stanchion. We tried a variety of different air pressures and eventually settled upon roughly 25-percent sag as the ideal state of tune for our east coast trail conditions.
Finally, and like any bike, fine-tuning of the seat height and rotation of the bars in the stem (along with position of the levers/ shifters) are all that separate you from blasting trails.
The Mount Up
There's no getting around this one: The Dakar Sixfifty B Comp is a pretty tall bike. The top tube does what it can to slope downward before the seat stay but even still you may want to mount up on a frame size smaller than you're used to before buying if stand-over height is on your short list of concerns. 5" of suspension coupled to the larger 650B wheels results in a bike with a fairly high center of gravity.
Getting into the saddle reveals a chassis that feels more compact than it looks from afar. The reach to the bars is a bit more stretched out than what's found on your average 26" wheel-equipped all-mountain bike but none of that cross-country bent backing stuff found here either. Fit and finish is surprisingly good- little touches like lock-on grips and 15QR remind that Jamis has been at this game for quite a while.
So the big question- what's it like to drop the hammer on the Dakar Sixfifty B? The answer in a single word would be smooth. That 30-speed geartrain means depending on your legs and lungs, you'll always have a gear combo that feels custom tailored to your needs. However, this isn't a wispy XC bike no matter how you slice it so there's little point in pushing a big gear until you're seeing spots. The Dakar is all about flow and those slightly larger wheels only extenuate this fact. We found the optimal means of enjoying "big B" was to start out in a low gear combo, to stay seated, and gradually build a nice head of steam. In doing so the charms of the 27.5-inch wheels, the rigidity of the 15QR and the benefits of just over 5-inches of suspension pay dividends.
Speaking of wheels; that seems to be what everyone wants to hear about so let us do our best to enlighten you as well. As you would probably suspect, rolling on 650Bs isn't quite as dramatic as the transition to full 29er for the average steady 26" rider but nor would it be mistaken for just another 26er either. Confused? Don't be. All we're saying is that the 650B has a unique feel- only slightly slower rolling than a 26"-wheel but quite sure-footed in roots and ruts. 29er diehards should really do themselves a favor and give a 650B a go when it comes time to upgrade due to the fact that they feel much livelier, especially during dead take offs. 26" riders on the fence about going bigger absolutely need to give one a test ride as many of the disadvantages of 29" wheels are toned down here.
Odds & Ends
As much as we'd like to get away with just spilling a little rhetoric about wheel sizes, there's surely a lot more about the experience of riding the Jamis that you'd like to hear about. Let's start with the tires shall we? Kenda Nevegals are always a favorite spec for the MBT test crew and the slightly larger diameter does nothing to change that fact. These meats are perfect for the frequent transitions from hardpack to roots, from roots to mud, and mud to sand that we east coasters call trails. They may be overkill for riders who frequent concrete-hard packed singletrack, endless flat rocks or paved bike paths but for everyone else, they're simply magic.
Cornering can be a mixed bag depending on how you treat the Sixfifty B. As we stated above, it's a taller bike so it likes to be finessed around turns and certainly responds more favorably to this than attempting to stuff it into a corner then power out with your legs. One of the major benefits to larger wheels is increased lean-over ability so capitalize by maintaining your cadence and leaning it into the curves.
Climbing is never effortless on a 30+ pound bike but again relying upon the bike's copious gearing makes the experience so much less painful than it could be. We found the best way up those ugly grinders was to stay seated, find a nice comfortable low gearing combination and to spin away. You'll never find those XC-style spurts of forward momentum here so there's no sense in wasting energy looking for it.
Descending is where the Dakar reminds you that the word "nervous" isn't a part of its vocabulary. Sure-footed 27.5" wheels with a tendency of tracking true even in the rough stuff, 5.1" of plush suspension and those pinpoint accurate 15QRs make going down hill a blast. This bike likes to hold a line! You'll find confidence you never even realized you were lacking the first time gravity grabs a hold of that front wheel.
Braking is adequate on the trails and a bit underpowered on the high-speed descents. Fortunately, since the Avid Elixir 3s offer decent actuation, steady modulation and a nice feel at the levers, this is a fairly cheap upgrade in the form of larger rotors if shuttle running is on your Sixfifty B agenda.
The way we figure it, there's two ways to approach the Jamis Dakar Sixfifty B: The first is to become obsessed with the gimmick of wheel size and to base your entire opinion of the bike upon it's choice of "intermediate" sized 650B wheels. The second is to forget all about the media-created controversy of wheel diameter and to simply let the ride tell its story. It is the latter that we tried to keep in mind while testing and the good news with that is we came away with a lot to appreciate about the Dakar's manners. This is a very versatile trail bike with a good honest spec sheet and at a solid price point. Whether or not the 650B wheel size is the wave of the future or just a passing fad is irrelevant to this bike and should be to you too.