Vital's SL eMTB Test Sessions - Karbon Bikes PowerLine SL Review 2

Founded in 2022, Karbon Bikes is a small company out of Massachusetts whose mission is to create unique and exclusive bikes around proven components. The PowerLine SL is their first lightweight model, aimed at offering full power performance in a sub-43 pound package via a 75 Nm Bafang motor and a 410-watt hour battery. How is this all possible? And what's a Karbon? We asked the same questions and were eager to see what this blinged-out mystery bike was all about. 

Highlights

• Carbon frame with aluminum rocker
• 29-inch wheels
• 150mm of rear wheel travel // 160mm fork
• Horst-link suspension platform 
• 410 Wh battery
• 75 Nm Bafang M820 motor with 250 watts of peak power
• Handlebar-mounted full-color LCD display
• Handlebar-mounted remote
• 64-degree headtube angle
• 77° seat tube angle
• UDH compatible
• Three build kits
• Sizes: S-L
• Verified weight: (Size L, X0 AXS) 43.56 lbs (19.75 kg)
• MSRP: $7,349 - $9,699 USD ($9,699 tested)

The Karbon eMTB lineup is a testament to their unique approach being built exclusively around Bafang motors. While Bafang is more prevalent within the budget-friendly commuter category of e-bikes, their frame-mounted drive units are rarely seen in the eMTB world but boast some promising numbers. With the Powerline SL, Karbon wanted to come as close to full power performance as possible while being as far from full weight as they could get. They achieved this with Bafang's M820 motor that weighs just a mere 5.1 pounds and pumps out 75 Nm of torque with 250 watts of peak power. Pair that with a 410-watt-hour battery that weighs just 5.7 pounds, and Bafang has developed a solid power-to-weight ratio. 

Looking at the user interface of the Bafang system, the full-color screen provides the most vivid picture quality of any display we've used. Displayed stats include battery percentage, assist level, speed, and a tripometer. Switching between the five assist levels is done with Bafang's ergonomic bar-mounted remote. Aside from navigating through the ride modes, there is a plethora of menus within the system, allowing for a unique level of personalization and mid-ride data. A battery data log can be accessed to show charge cycles on the battery, average battery temperature, cell voltages per cell, and firmware updates. With how much information is available on the bike itself, app integration is less necessary. The Bafang Go app acts more like a standard cycling computer that can display navigation and data in addition to the information already displayed on the bar-mounted display. 

The full 29-inch PowerLine SL lands square in the middle of the all-mountain category, with 150mm of horst link driven rear wheel travel paired to a 160mm fork. The 64-degree headtube angle helps maintain consistent handling over a wide variety of terrain, while a lengthy 457mm chainstay keeps both wheels planted. A 77-degree seat tube angle creates an efficient pedaling position and places rider weight firmly into the seat. The PowerLine SL was the only size large bike in the test, with all other bikes being XL. This meant that the 1267.6mm wheelbase and 474.2mm reach were the shortest in the group.

Karbon offers the PowerLine SL in three build kits and three sizes. Builds range from $7,349 to $9,699 for the X0 AXS build we tested. Frame construction consists of high-modulus carbon fiber front and rear triangles with an aluminum rocker and a custom paint finish with holographic decals. Our build kit was highlighted a SRAM X0 Transmission drivetrain, RockShox Ultimate level suspension, Magura MT7 brakes, and Karbon's own carbon fiber handlebar and wheels. The PowerLine SL was the fourth lightest bike in the test at 43.56 pounds (19.75 kg). It is worth noting that the images on Karbon's website do not reflect the actual build specs, so be sure to read the description closely when shopping. 

The PowerLine SL was hands down the wildcard of this Test Sessions due to its unfamiliarity with our testers. However, with a tried-and-true suspension layout and quality components, it proved to be an easy bike to hop on and feel comfortable. What took the most time to adjust to was learning the ins and outs of the Bafang system. 

Test Sessions has long been Vital's way of placing a bunch of similar bikes head-to-head to see where each excels and what sets them apart to help riders better understand which bike best suits their needs. This year, we had eight SL e-bikes, and three testers. This article just covers what we thought of Specialized's Levo SL. To learn more about the other bikes tested, check out our complete SL eMTB Test Sessions. 

Meet the Testers

 Jason Schroeder

• 29 years old
• 6-foot (182 cm)
• Weight: 180 lbs (81.6 kg)
• Years e-biking: 4
• Riding Style: Relatively upright with weight more rearward than most. Enjoys a sneaking straight line or ripping jump trail.

 Lear Miller

• 32 years old
• 6’ 3" (190 cm)
• Weight: 185 lbs (83.9 kg)
• Years e-biking: 3
• Riding Style: “Freeracer” after 15 years of racing, I like going fast. But the airtime counter is really the only clock I’m paying attention to these days.

Jonny Simonetti

• 30 years old
• 6' 4" (193cm)
• Weight: 225 lbs (102 kg)
• Years e-biking: 5
• Riding Style: Skatepark inspiration. Try to stay smooth and pedal as little as possible. 

Jason's Impressions

What's The Bottom Line?

The PowerLine SL stood out not just because of its crazy paint job or Bafang motor, but because I didn't even know the brand existed before this test. I'm always filled with equal parts hope and hesitation when riding a new, unknown bike, and the PowerLine SL proved to be more fun than I expected, with a lot of promise for the future. It rode as light as the scales confirmed, providing a very 'SL' feel on trail that had me forgetting I was piloting an e-bike. I had no problem moving the bike around, whether that be pulling for natural doubles, pumping through a berm, snagging a high line before a switchback, or tossing in sneaky manuals. Active and lively were hot words surrounding the performance of the PowerLine SL. The suspension offered great support on big hits or when pushing my weight into the bike. However, small bump compliance was lacking, and square-edge compressions were a bit harsh. But that was fine—I was way more motivated to go jump around down the trail on the PowerLine SL than blitz into a rock garden. 

I was really excited to try the Bafang motor for the first time. Unfortunately, it was less impressive than the other motors in the test. The 75 Nm of torque felt more similar to the 60 Nm provided by the Fazua system, and it was all delivered right off the bat. This was nice when pedaling in a higher gear or at slower speeds, but the power topped out sooner than I wanted. I end up having to lower my cadence and intensity to stay within the power band. The 20% battery conservation feature was also a bummer when it kicked on halfway up a climb on the last day. It felt a little pointless to have 19% battery life remaining and only receive what felt like half-power. Maybe the battery should just be out of 80%?

Even though the PowerLine SL wasn't the most expensive, it still carries a premium price tag. Yes, the components are solid, and you can spend way more on an e-bike with worse parts. But I think there needs to be more than just component spec to push someone into buying a bike from a small, lesser-known brand. In the test, the PowerLine SL and the Santa Cruz Heckler SL both cost $9,700. The PowerLine SL has a few nicer components, but the Heckler SL is backed by years of proven bike development and an extensive dealer network. There is always risk in buying a bike from a new brand, and while I think the PowerLine SL is a very playful, fun bike, I think most riders will require some additional wow factors to take the leap and purchase one of their bikes.  

Jonny's Impressions

What's The Bottom Line?

Being the underdog in the test with some proven brands and motor systems is no small task, but the Karbon surprised me, especially with how the Bafang system works. The bike is very easy and comfortable to ride up to a limit, pedaling uphill requires very minimal effort to get full torque out of the system but once it is achieved there is not much left on the end of peak watts. The same goes for descending performance, it has a conservative feeling that allowed me to open it up when appropriate, but required a bit more finesse in more aggressive terrain. The Powerline SL brings a new approach to the lightweight category and will cater to riders who prefer more of a “tow rope” feeling up the hill and are interested in more than just flat-out descending performance. 

Lear's Impressions

What's The Bottom Line?

The PowerLine SL was a lively, quick-maneuvering bike that rode as light as the scales showed. It did perform best as a tight terrain navigator rather than a ripping descender, and I didn't feel the urge to seek out the gnarliest sections while riding the bike. I was plenty happy popping and dicing up the flowier trails. The aesthetics of the PowerLine SL were a love-hate relationship. On the one hand, the paint job is stunning and unique, but on the other, it's loud and not exactly my cup of tea. Being able to easily access a lot of information without requiring an app connection was a strong point of the Bafang user interface. However, power delivery was something I felt like I never fully figured out to maintain a consistent speed or cadence. Additionally, the limp mode imposed at 20 percent battery life reduced power drastically and was cumbersome to pedal. Even though the build we tested was around mid-pack for the price, considering the PowerLine SL as my daily driver would require a major value or performance proposition to sway from the other proven brands included in the test.

A big shout out to Tannus, Feedback Sports and Maxxis for supporting Test Sessions!