Bulls Copperhead EVO AM4 750 Review Overview
Bulls, a German bike manufacturer, has been making bikes since 1995. They created their first e-bike in 2009 by partnering with Bosch for their motor system, making Bulls one of the first companies to have an electric mountain bike. I’ve been riding and reviewing their bikes since 2016 and have always had a great experience with them.
Recently, we reviewed the Bulls Copperhead EVO AM4 750. That’s a lot of cryptic jargon, but it breaks down like this. Copperhead is the name of this specific frame, EVO is Bulls’ way of saying it’s an e-bike, AM is for All-Mountain (as opposed to longer-travel bikes including Enduro and Downhill), and 750 designates that it’s using a Bosch 750Wh battery, the current highest-capacity battery they make.
This is the top-of-the-line Copperhead. There’s also a 3, a 2, a 1.5, and a 1 version, each less expensive as the number goes down, with lower-spaced components.
It has 150mm of travel front and rear, provided by SR Suntour. The 36 mm stanchions on the fork are beefy, and you can adjust the high- and low-speed compression, rebound, and air pressure. Some people will complain that it doesn’t have a higher-end Fox or Rockshox, which would significantly increase the bike’s price.
On the other end, Shimano XTR components are everywhere on this bike. The drivetrain is a 1×12 setup with an XTR derailleur and a 10-51T cassette. Shifting is buttery smooth with a trigger shifter that can go up or down up to three gears at a time. The smooth shifting is impressive, as this specific bike has been used at several races and on the podium a few times. The Bosch motor takes 1000 sensor readings per second, so when it feels you shift, it cuts the power for an imperceptible amount of time to reduce stress on the drivetrain.
Brakes are also XTR, hydraulic brakes with 203 mm rotors for more leverage and a quad-piston caliper in front and dual-piston in the rear, with great modulation on both.
There are pre-wired MonkeyLink magnetic receivers for MonkeyLink lights or reflectors, which also lets you use power from the Bosch battery to power the lights. There’s an SP Connect phone mount installed that works with an SP Connect phone case that is extremely sturdy.
The Motor
Bulls generally use either Brose or Bosch motors in their bikes. For this one, they went with the new Bosch Smart System, including a Performance Line CX motor that offers 250 W and 85 Nm of torque to help you get up steep climbs. The 750W battery is big and heavy at nearly ten lbs, but it should get most riders over 25 miles on a single charge. It’s integrated into the downtube, and you can remove it for charging or charge it on the bike. It’s slightly different than other models and is not backward compatible. The charging time is longer than that of other bikes because of the high capacity, so it can take up to 6 hours to fully recharge the battery.
The controller is stealthy and mounted on the left side of the handlebar, with a simple on/off button and mode toggle, with LEDs lighting up to tell you how much charge your battery still has. Five lights change colors before they turn off, giving you ten percent increments. Besides, one LED lights up green when you’re in Eco mode, light blue when you’re in Tour, a deeper blue when you’re in eMTB mode, and red when you’re in Turbo. You can switch on integrated lights by holding the plus button for one second, and if you want to turn on the walk-assist, hold the minus button for at least one second and continue to hold it while walking.
You can even customize the power settings on your bike using the eBike Flow app on your smartphone. Using the app, you can even install over-the-air firmware updates, so you don’t have to take it to a Bosch technician at a bike shop.
The Ride
We chose a local trail that we could ride to, not have to drive to. It’s six miles to the trailhead, and the last mile is steep! I’ve emptied a few lesser bike batteries on that hill just getting to the trailhead. Not this one. It used about 20 percent of the battery to reach that point, and I used eMTB mode on the way up. eMTB mode isn’t a set power amount, like Eco, Tour, or Turbo. It’s dynamic, reading your legs’ torque and varying the motor’s power output between Tour and Turbo. It’s quite impressive, easily the most natural, and a favorite.
There are steep trails and a fun jump line that kids have built, with big jumps that this old guy ain’t hitting and rollers next to them. The rollers are fun; it’s like a pump track built on the side of a mountain. It’s a good time, and I looped through them a couple of times before exploring other trails with stunning views of Los Angeles below.
I said earlier that shifting was buttery smooth. There’s one caveat, however. When I was climbing something steep and shifting three gears up at once, there would be a shock through the system and a nice loud Ping! from the stress on the drivetrain. The 165 mm E-Thirteen cranks were long, and we never had a pedal strike.
The suspension worked precisely as well as I thought it could. When we first got the bike, it felt a little stiff, but I checked the sag, and it was right where it should be. A couple of adjustments were all it took to make the suspension plush. The bike climbs extremely well. Bosch’s power delivery is excellent, even on really steep climbs. The geometry is slack, but not crazy slack, so it climbs and descends comfortably. The reasonably long dropper post gets the seat out of your way for bombing down trails and brings it right up to where you need it to be for ascents.
Our only potential complaint is that the saddle is hard and slippery. We’d look at replacing it with something more comfortable.
The brakes are outstanding and inspire confidence. Even on crazy long descents, they didn’t heat up hot enough to fade (thankfully!).
Bottom Line
For the price, it’s easily one of the best e-mountain bikes we’ve ridden. It won’t be as good as the Canyon Spectral:ON we tested, but that bike is $3,000 more. The closer match is the Yamaha YDX Moro 05, which comes in at a couple of hundred bucks less expensive, but not its higher-specced sibling, the YDX Moro 07.
We thought the ride quality was fantastic; there’s more power than we needed from the Bosch CX motor, and the new Smart System adds new functionality and control. And keep in mind, it performed this well after being truly battle-tested. Chris Kernaghan, Marketing Manager of Bulls Bikes USA, raced it to a first-place win in his age class on this very bike, and it’s been ridden and tested by quite a few others. It’s been ridden hard and wet quite a few times, with the scratches to prove it. I’m used to getting brand-new bikes. This one was a testament to how well it performed after several beatings.
