Electric Bike Action Bike Test: Bulls Copperhead EVO AM 4 Trail Bike



redesigned it from the ground up. The motor itself, including the casing, is tiny compared to the third generation. In fact, the motor lost almost 3 pounds and, at nearly half the size, allows for shorter chainstays.

A Shimano XTR 1×12 drivetrain offers all the range we could have asked for.


The new motor has the same 75 N/m of torque that the older ones did, but now it can provide more support. The previous generations topped out at a maximum of 300-percent support, and the Gen 4 motor goes to 340 percent. It breaks down like this: 

ECO = 60%

TOUR = 140%

eMTB + 140–340%

TURBO = 340%

The e-MTB mode offers stepless support based on rider-leg torque input. In other words, the harder you pedal, the more assistance it gives you. This is like having an automatic transmission that gives more support when you need it, less when you don’t. If you like to “lock in” one more predictable level, you can. Support on all levels goes to 20 mph (15.5 in Europe) and 120 rpm. There’s also a walk mode to help when you have to walk up a hill with the bike.

This is the first CX motor to use a normal-sized front sprocket, whereas previous generations had a much smaller sprocket that had to spin 2.5 times for every revolution of the crankarm. Because it’s a mid-drive, it won’t overheat on long climbs. There are also some fins built into the design to enhance cooling. 

The motor Bulls chose for this is a 625-Wh Bosch PowerTube that’s completely integrated into the downtube but still removable. This is the biggest battery Bosch makes currently and offers tremendous range. 

The RockShox Super Deluxe RC rear shock offers plenty of options for control and offers a really plush ride. Note how much smaller the new Bosck CX motor looks.


The Bosch Kiox display is one of our favorites and provides even the geekiest rider with a plethora of useful information. The full-color main screen is simple, really bright and easy to read. Mounted top center in front of the stem, it’s held on by a clever system of magnets so it can pop off in case of a crash or if you want to take it with you. Removing it disables the electrical system, which makes it somewhat of an anti-theft feature, as it will only power up again when the same Kiox display is reconnected.


“There was nothing we threw at the Bulls that it didn’t take in stride.” 


Among the connectivity and features, it can connect via Bluetooth to the eBike Connect app, which can track your GPS and riding data, and also connect to a heart-rate monitor. The latter is really helpful for anyone using an e-bike for training, as you can use the HRM to keep yourself in the perfect training range, regardless of terrain. You can turn on your bike lights from the display and connect your phone to it to charge while riding.


With a generous 150mm of travel, the Copperhead is made for all-mountain riding, hence the “AM” designation. Owing to its $8000 price tag, it’s not for the faint of wallet, but you get a lot of quality components and the latest technology from Bosch.

Photo: Pat Carrigan



For our first ride, we set the sag on the RockShox suspension at 25 percent. That offered a good starting point, but almost felt a little stiff.

Power from the new Bosch motor is thrilling, and…


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