The Karmic Koben is one of the most promising electric bikes to grace the front page of Kickstarter. It strips away the complexity that plagues many other ebikes and offers solid performance and exceptional value all in a relatively lightweight package.
When the Koben was first announced just over a year ago, it promised to deliver a rigid-frame single-speed electric bike with a target weight under 40 lbs, a novel rebuildable battery pack, and a mid-drive motor with market-leading torque. The upmarket Koben S model, though not as lightweight, teased an interesting gearing solution: a Nuvinci N380 continuously-variable transmission.
Just one year later, Karmic has sold hundreds of Kobens and the bikes are now being delivered to early campaign backers, which is quite a happy outcome indeed, especially in light of the vile prognostications of crowdfunding campaign naysayers (“The company will go out of business before you ever see your bike!!!”).
Karmic Koben S Overview
Both the Koben and the Koben S lack any kind of suspension, and as a result, the bike weighs a bit less than its competitors and is easier to lug up and down stairs.
On my first day with the bike, the ride quality felt bumpy and uncomfortable, however, after putting in some more time in the saddle, the rigid frame started to grow on me, and the ride quality didn’t seem to bother me as much. I find that rigid bikes are a love-it-or-hate-it thing, a subjective personal preference, however, my experience with the Koben illustrates that it’s possible to have a strong preference for front suspension forks and yet still be able to appreciate a rigid bike.
Another factor that makes this rigid bike easy to love is that it comes with relatively thick 1.75″ x 27.5″ Panaracer Gravel King tires. They’re thick enough to soak up a good amount of road bumps, and their lack of center tread means that they roll more efficiently than the vast majority of tires on the market, giving the rider both a comfortable ride as well as a boost in efficiency and speed. In fact, the tires’ rolling efficiency was the single most surprising thing that I discovered in the week I spent with the Koben. Often, I’d find myself cruising at 20 or 25MPH on flat ground and I’d stop pedaling, the torque-sensing pedal assist would cut off immediately, and yet a block or two later–with no pedal input–I seemed to be going the same speed as I was blocks earlier, giving me the perception that these tires had somehow managed to eliminate both rolling resistance and aerodynamic drag. Obviously, that’s not physically possible, but the performance of the Gravel King tires was striking. Until riding the Koben, I had no idea that tire tread (or the lack of it) could have such a striking effect on the performance of a bicycle. If you try out a Koben S with these Panaracers, you’ll hear the gospel, too.
Motor, Drivetrain, and Performance
The star of the show on the Koben is most certainly its mid-drive motor, the Bafang Max. This motor offers a market-leading 80Nm of torque, and has proved to be so powerful that it vanquished even its German arch-rival, Bosch, in a 24-hour race at the Nurburgring.
The 350W Bafang Max motor in the Koben is almost completely silent. The only time that I can really hear the motor is when accelerating from a stop to about 8MPH – above that speed, I’ve found that the wind noise drowns out any noise coming from the motor itself. Though I’m not an expert on the Bosch mid-drive system, I do think that the Bafang Max is a bit quieter. In fact, the Bafang Max is even quieter than geared hub motors, though direct-drive hub motors still take the cake as the quietest ebike motors on the market (though they also come with their own set of disadvantages).
The Koben S shifts gear ratios using its novel Nuvinci N380 CVT, which notably can be shifted under power, whereas derailleurs and internally-geared hubs require reduced pedal input during shifting. Given that you don’t have to wait for your gears to shift with a CVT, accelerating on a CVT-equipped ebike is less complicated, but it does take some getting used to. Changing the ratio is accomplished by twisting the Nuvinci’s twist grip shifter: twist it forward for climbing hills, twist it backwards for higher speeds and when descending hills. The twist shifter does offer some noticeable resistance to twist input, and as a result, it’s seemingly impossible to access all the the CVT’s infinite gearing ratios, so you’re limited to the ratios that your twist input can comfortably come to a stop at. This prompted me to think that it might be better to use a trigger shifter to shift gear ratios on the Nuvinci CVT. The downside of a trigger shifter would be that you wouldn’t be able to access the infinite gear ratios offered by the CVT, but since I can’t seem to do that with the twist shifter anyways, I’d rather be able to maintain a strong, continuous grip on the handlebar grips and then just use my thumb for shifting as opposed to having to reduce the strength of my grip and twisting the shifter one way or the other. After a long day on the bike, the repetitive action of reducing the amount of weight on my right hand and twisting the twist shifter resulted in some noticeable stiffness and discomfort in my right wrist, which clearly wasn’t used to the twisting motion.
The performance of the Koben S is fantastic. I was able to easily cruise at 28MPH when using the bike’s highest pedal-assist level (5), and found that the bike provided assist even beyond its stated top speed, which matches my experience with other S-pedelecs from manufacturers like IZIP and Stromer. In fact, the end-user can even set their own preferred max-assist speed (for off-road use only!) right on the bike’s screen, which is a really useful feature that I haven’t found on any other production ebike. This feature could enable you to ride your bike with a 20MPH max-assist speed in certain jurisdictions, increase it to 28MPH for California and Switzerland, and raise it to 37MPH (the maximum setting I found on the display) for use on an oval track. The formidable high-speed performance of the Koben S is especially surprising considering that the motor is rated for only 350W of continuous power, which would lead me to believe that the bike should only be able to maintain a speed of 25MPH or so. Competing models with 350W motors like the Kalkhoff Integrale offer assist up to 28MPH but are only capable of comfortably cruising at 24 or 25MPH, and actually hitting 28MPH requires too much pedal input from the rider to maintain that speed for more than a minute at a time. It takes approximately 900W of motor power to cruise at 28MPH with a typical hub motor, and my experience with mid-drive bikes like the Kalkhoff Integrale shows that some 350W ebikes quite simply aren’t up to the task. The Koben S, which has a more efficient drivetrain than a hub-motor bike, as it has the mechanical advantage of the CVT’s gearing, didn’t seem to have any problems maintaining 28MPH even in a slight headwind, so this motor must either put out more than 600W of peak power or it’s just really efficient due to its mid-drive motor and CVT gearing setup. Speed demons shouldn’t make the mistake of ignoring the Koben S, because its high-speed cruising performance is comparable with the finest S-pedelecs on the market today.
When it came to climbing hills, the Max drive combined with the highest gear ratio on the CVT was able to tackle just about every hill I encountered. I took the Koben S on one of San Francisco’s steepest hills (25%+ grade) and was able to tackle it without dismounting, however, I was forced to ride in a zig-zag pattern so as to reduce the apparent grade and be able to maintain my speed. If I had tried to ride straight up, I only would’ve made it half-way up the hill. Is this is a sign of weakness? Hardly. In fact, I’ve yet to find an electric bike that I could ride straight up the steepest hills in this city, and the Koben S performed better on hills than any bike I’ve tested so far, so if anything, I’d say the Koben S’ enviable hill climbing performance is a significant achievement.
The 44V, 10.4Ah, 460Wh battery pack offers slightly above average energy capacity and offers above-average range. I found that this battery combined with the efficient Bafang Max motor ended up giving me around 50 miles of range when using the lower pedal assist modes. Karmic pegs the Koben S’ range at 45 miles, but I think that number is conservative. In fact, I don’t think 65 miles of range is outside the realm of possibility, especially considering that Bosch-powered electric bikes are capable of that range with smaller 400Wh battery packs.
My daily driver is a 500W direct drive hub motor electric bike and is a bit of a power hog, and I found that I was able to ride the Koben S without the significant range anxiety that I experience on my regular ebike. The improvement in range is especially apparent in hilly areas, where the Koben S’s efficient mid-drive motor absolutely shines.
Brakes, Wheels, Frame and Fork
The TRP hydraulic disc brakes on the Koben S offer superb power and modulation. I love them, however, I found that I could only comfortably fit two fingers on the brake lever, and trying to fit a third finger on it made for an uncomfortable finger position in which all my fingers were slightly angled to the left instead of extending straight out from my natural grip. As it turns out, this two-finger setup was intentional. “The brakes we use are specifically a two-finger lever design,” says Karmic Bikes founder Hong Quan. “Because the braking power is so strong, using a three or four finger lever would just mean instant brake lock-up (tires skidding) and very little modulation.” The TRP Quadiem hydraulic disc brakes that are spec’d on the Koben S are heavy-duty mountain bike brakes that have been ridden to victory in World Cup Downhill races, and as a result, no more than one or two fingers is necessary, as braking with more fingers could lead to unexpectedly strong braking force that might cause a rider to get thrown off-balance. Luckily, the levers are positioned for two fingers and nothing more, so I never had any trouble with excessive braking force, but it’s reassuring to know that when I need lots of braking power, I’ve got plenty in reserve.
The frame of the Koben S is very unique compared to its competition. The most obvious thing to note about it is its striking color, an electric blue. The other color option thus far is a bright, slightly bronze-y orange that is very conspicuous but perhaps a bit too ostentatious for some buyers. Regarding the frame design, it’s a modern take on a rigid mountain bike frame, with the only big difference being that it has horizontal single-speed-style dropouts in the rear so as to properly tension the chain, as there is no chain tensioner. The frame also has rear rack braze-ons on the seat stays so you can turn your bike into a touring and commuting machine. The front fork has fender mounts, and though I don’t see a convenient way to mount a front rack, Quan reports that customers have successfully mounted them.
For those questioning the selection of the rigid front fork, keep in mind that the geometry of the Koben and Koben S does allow you to substitute a front suspension fork after you buy the bike. In fact, at Monterey’s Sea Otter Classic this year, there were two suspension-equipped Kobens in the running at the inaugural electric mountain bike race, and one of the Kobens actually took third place in the overall standings.
The Koben S is a solid performer, with powerful hydraulic disc brakes, a torquey mid-drive motor, fantastic range, an attractive frame and a novel transmission. At $2,799, the Koben S represents a good value considering the top-shelf specifications, and I found no evident weaknesses on the bike. I recommend this bike for road use, commuting and light touring.
The Koben S was originally available on Kickstarter, however, Karmic now has Koben and Koben S models in stock and ready to ship, so customers no longer have to wait months to get their hands on one.