- A high-end, full suspension, electric mountain bike, with the high-torque Brose S mid-motor, and a high-capacity 37 volt 17.5 amp hour Lithium-ion battery, excellent weight distribution with hidden drive systems
- Rugged all-mountain performance with 150 mm RockShox air suspension front and rear, 15 mm and 12 mm thru-axles with Boost hub spacing for sturdy spoke bracing angle, larger 2.8" plus sized tires improve traction and float
- Available in three frame sizes for optimal fit, grey and black frame color hides the battery and motor, the motor is very quiet and smooth, internally routed wires are protected and concealed, the control pad is compact and less showy
- One of the more expensive models from Bulls due to higher-end components, the Marquardt display has an integrated Micro-USB port, premium Schwalbe tires, Ergon grips, Kind Shock seat post dropper, and Shimano Deore XT drivetrain with Shadow Plus one-way clutch to reduce drops and slaps, standard sized 38 tooth chainring
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The E-Stream EVO AM 4 is a category leader in the Bulls ebike lineup. For all mountain riding, it offers longer 150 mm (~6 inch) suspension front and rear. Both air shocks offer pressure, rebound, and compression adjust to optimize performance for different rider weights and terrain; climbing or descending. As with many of the higher-end Bulls products, the E-Stream EVO comes in three sizes for optimal fit. As a medium sized, lighter weight rider myself (weighing ~135 lbs), I appreciate that the suspension can be sagged and mounting/dismounting is easier because of the seat post dropper and angled top tube. The Kind Shock Lev-Integra dropper post can be set at any height vs. 10 step increments, and it comes in handy when transitioning from climbs to descents. This electric mountain bike looks beautiful, you can hardly tell it has a motor because the Brose S mid-drive is so compact and quiet. The battery pack seats up into the downtube vs. being bolted onto the top, and most of the electrical wires, shifter cables, and brake lines are internally routed. Furthermore, the frame is painted dark grey with black accents, and this allows the black accessories, such as the display panel, to blend in. It’s one of my favorite e-mountain bike models to date, because it offers such efficient and responsive riding, allows you to go further with a high-capacity battery, and spares no expense on brakes, drivetrain, accessory options, grips, or tires. Yes, it costs a bit more than your average all mountain model, but the price is not excessive for what you get. Bulls is a German brand with global distribution, backed by a network of dealers in Europe which launched it as an “in house” brand. I have been reviewing their e-bikes since 2016, heard great things from dealers and customers, and always received quick support and follow up from their leadership team, which are based in Southern California. There are a few trade-offs and things to get used to with this bike, namely the compact Marquardt display panel, that I’ll get into later.
Driving this bike is one of my favorite new mid-drive motors, the Brose S. I have always appreciated how compact, lightweight, and quiet the Brose drive systems are, and apparently the S (for Sport) is 1.25% more efficient, to help extend range, while also being 15% more powerful! So what’s the catch? Perhaps it weighs slightly more than the original Brose T, but at ~6.61 lbs it is still quite a bit lighter than the competing Bosch Performance Line CX. I think the other trade-off from the Brose T is that it produces more noise. Inside all of the Brose mid-drives is a Gates carbon belt drive that reduces vibration between your cranks, the spindle, and the internal gearing. It’s quiet and very smooth, there’s less of a vibration feel, but it is still extremely powerful, offering up to 90 Newton meters of peak torque. Unlike a lot of competing systems, the Brose motor controller seems to rely heavily on pedal torque vs. cadence or any set level of pedal assist. I demoed this a bit in the video review above, but the short explanation is that you can be riding in the highest level of assist but still be riding slowly without the motor kicking on much at all… if you aren’t pushing very hard. It feels very natural and support is there almost instantly when you do exert pressure. One feature this motor controller does not offer is shift detection, but the power cuts out very quickly as you reduce pedal torque, so it’s best to ease back when shifting in order to reduce mashing (chain, sprocket, and derailleur stress and wear). You and the motor have access to an 11-speed drivetrain for climbing and descending. As you shift through the gears, you and the motor get an efficiency benefit… and the motor will support zero to ~20 miles per hour with 120+ pedal rotations per minute. This means that you can spin quickly verses having to shift to a higher gear in order to reach higher speeds. Some of the older motors, and even some of the newer Yamaha and Shimano motors don’t seem as capable at higher RPM’s and it’s something I personally care about, because I have a sensitive knee. I’d much rather spin at higher speeds with less pressure than lumber along, or have to shift gears frequently as terrain changes. The chainring is a standard 38 tooth, which could be swapped out easily, and the cassette offers 11 to 42 tooth sprockets. I was able to climb terrain so steep that the rear wheel began losing traction and then descend at upwards of 35 miles per hour comfortably. The derailleur is Shimano Deore XT with Shadow Plus, and that means it’s mounted below the right chain stay and tucked in while also having a one-way clutch to increase resistance and pressure that negates chain slap and drops. The standard chainring helps to elevate the chain to reduce chain slap anyway (compared to the smaller proprietary sprockets that Bosch uses), and it might not suffer from chain suck as much on the bottom because there’s extra space next to the motor casing. Mud and grassy debris should be cleared by the E-Thirteen TRS+ full-surround chain guide, which virtually eliminates drops and might also clear your pant leg (if you’re riding with loose pants for some reason). On that note, the left chain stay does have provisions for adding a kickstand if you so wish, perhaps for weekday use – riding around town.
Many of the Brose powered electric bikes from Bulls have higher-than-average battery capacities, and this is a highlight for me because they don’t actually weight that much more. Looking at 7.1 lbs for a 647.5 watt hour pack is impressive when you compare the 500 watt hour Bosch Powerpack at 5.8 lbs or their heavier Powertube at ~6.15 lbs. You’re getting 30% more capacity for a 22% increase in weight… and that’s comparing to the lighter Powerpack. You can do a lot with 150 extra watt hours, especially on an efficient mid-drive setup. The battery pack is not perfect however, seating up into the downtube vs. down from the top. It might just be the demo model I tested out, but the pack sort of flopped out when unlocked vs. having a two-step button like the Bosch Powertube. The pack is contained in plastic vs. tougher aluminum alloy but does have a thick rubber guard all the way along the bottom. I was told by Bulls that the pack itself is similar to 2017 models (which had a foam sticker vs. integrated rubber) and that the packs could be interchangeable, but might not look great. This is one area where Bosch has a lead, all of their packs have remained the same and are easier to find and swap out on-location. It can be difficult to fly with high capacity Lithium-ion batteries, and being able to rent or borrow on location is great if you want to bring your own personal bike. The charge port on this battery is fancier, and interfaces with a high-speed 5 amp charger for quicker fills… but I have read that this can stress the cells more than slower 2 or 4 amp charging. You can protect your packs from premature wear by storing them in cool, dry locations vs. extreme heat and cold. And, you don’t have to remove the pack from the bike at all to charge it, if you prefer. This could reduce the potential for accidental drops, because of the flop-out unlock situation and limited grip and handle design, the pack can be surprisingly heavy when the weight is instantly transferred into your hand or you’re even pulling it down from the downtube (working with gravity). Remember, by default there is no kickstand, so you might also be balancing the bike. It could be best to lay the bike onto its left side when working with the battery… just be careful with the larger 203 mm disc brake rotors, don’t touch them because the oil from your fingers can wreck the pads over time. A final not about the battery pack and charging interface is that it’s magnetic, and iron filings and other debris can stick to the end of the plug, just brush it off occasionally to ensure a good contact for charging.
Another exciting but mixed feature of the new Brose system featured on this ebike, is the compact Marquardt display panel. It’s compact, which allows it to blend in and possibly avoid damage if the bike is dropped or crashed. It offers lots of menus and settings (way more than the comparably sized Bosch Purion), but has an additional joystick button thing that could get worn out quicker. And, I’m told that it offers active Micro-USB charging through a port on the right side. This could be a huge win if you like to listen to music or use your phone for GPS navigation (as we did for the longer adventure ride in the video above). The actual LCD display is much smaller than the Purion and could be difficult to read at times, though it is brighter in terms of backlighting. I found that the location of the Marquardt on this particular ebike was difficult to reach because of the seat post dropper lever. I had to reach over and around the dropper lever, then across the brake lever mount. If I were setting the bike up, I might angle the dropper lever down or up more to create space. It might even be possible to mount on the right side, between the brake lever and trigger shifters. There’s a lot of room for experimentation here, and I want to call out the two-finger Magura brake levers, which have adjustable reach and can be spaced out to use with just one finger, if you prefer. Overall, the cockpit is clean and simple, I love the locking Ergon grips and appreciate the slightly raised handlebar and short stem for comfortable downhill riding. I guess, coming back to the display, there was some confusion about how to change units, and I was told that Bulls is releasing a Bluetooth app at some point. I wish I could say more about that now, but perhaps you can chime in with comments below if you have seen and used it. Apparently, it will also connect to a Bluetooth heart rate monitor? Though, many of the monitors I see have used from Garmin use Ant+ vs. Bluetooth. I wish that the Marquardt showed a greater number of batter bars or even a battery percentage vs. just for bars, and the range estimate menu seemed static vs. dynamic as we used the up and down keys to select more or less power. This is one area where the Bosch displays are really nice. Overall, if you have ridden a Bosch CX powered ebike and used the newer eMTB drive mode, I would say that it feels a lot like all of the Brose S drive modes. It’s just fluid and responsive, not too much work, but not as zippy and on/off as many of the other systems. It’s one of my favorites and one of the most natural. Using the joystick to navigate through menus, even having to be in the assist menu before the up and down keys worked, was sort of frustrating. I didn’t realize that you could use the joystick to go up and down in some areas until after a lot of riding. It’s amazing that they packed so much into this display, and I appreciate the dedicated light button (if you add lights to the magnetic MonkeyLink interface on the stem and seat post clamp). There’s also a walk mode if you hold the up arrow while already in one of the three or four assist levels. It went pretty slow at first, until I shifted gears up… but you’re probably always going to be starting in a lower gear when getting off to walk (assuming you couldn’t balance on a climb) so I wish it was faster and measured wheel speed vs. having a set rate. Think about the moment you finish walking and then hop back onto the bike… with the gear set high so walk mode would be faster, now you have to mash gears to shift low to pedal, it’s frustrating :/
Thankfully, there aren’t that many truly frustrating things about the BULLS E-Stream EVO AM 4 and the Brose S setup. Nor should there be for such a price, right? I had a blast riding this model, loved how blacked-out it looked with the muted color scheme and even the anodized black stanchions on both RockShox shocks. If you’re not interested in answering questions from fellow cyclists, this ebike is one of the stealthiest around (in terms of looks and noise) and the wider hubs and plus sized tires make it a blast to descend with, there’s very little deflection, weight is positioned well on the frame and it handles well. I love that there was room to squeeze in a bottle cage mount at the downtube, and that there’s a fancy magnetic MonkeyLink option there for easily reaching and re-attaching fluids as you ride. If price were no object, this would definitely be on my shortlist of leading electric mountain bikes. There’s a bit less trust of the Brose motor in my mind because I have seen Bosch for so much longer, but I do trust Bulls and it’s nice to know that this new Brose S model is a refinement of the earlier T that has worked so well. Bulls improved some of the rubber covers around the charging port and key hole from 2017, but it’s still not as seamless as some other companies. Weighing in at ~55 lbs, the bike is heavier than a hardtail but the larger 203 mm hydraulic disc brakes always felt good, even on longer descents for this ride. I felt secure with the tires, brakes, and weight, and it just felt good. Big thanks to the Bulls team for partnering with me on this post and providing a couple of bikes to compare back to back, it was awesome to see the Powertube and Purion from Bosch next to the Brose Marquardt and proprietary Bulls battery integration. As always, I’ll do my best to answer questions below and you can get other opinions directly in the Bulls Ebike Forums.
- The Brose S (Sport) motor has become one of my favorite ebike mid-drive systems (right up there with the Bosch CX), it’s 15% more powerful and 1.25% more efficient than the Brose T while remaining compact, quiet, and relatively lightweight at 6.61 lbs
- Because the Brose mid-motor uses a traditionally sized chainrings (38 tooth in this case), it doesn’t require a reduction gear, won’t suffer from chain suck or chain slap as much, and can be swapped out with other chainrings more easily
- You should get excellent range on this bike, because the motor allows you to leverage 11 gears to climb easily and the battery capacity is way above average with 37 volts 17.5 amp hours for ~647.5 watt hours total
- This e-bike looks amazing because the motor is so compact and built into the frame, the battery actually seats up and into the downtube, and the frame color is dark grey and black – which blends everything together (including wires, which are internally routed across most of the frame)
- Most of the ebike chargers I see are 2 amps or 4 amps, but this one uses a 5 amp charger from BMZ, it plugs into the battery with a magnetic EnergyBus connector that will simply pop out if tripped over, I love how you can charge the pack on or off the bike and am happy that the battery is higher capacity because bringing the charger along would be less fun since it’s bulkier and weighs ~2.6 lbs vs. just 1.5 or ~2 lbs on most other chargers
- Relatively lightweight for an all mountain electric bike with longer travel 150 mm ~6″ suspension, thicker stanchions, sturdier joints, and a high capacity battery pack, it weighs ~55 lbs total and could be reduced slightly by running the tires tubeless (they are tubeless ready)
- Available in three frame sizes so you can improve fit, the air suspension is more highly adjustable than spring, you can sag it to match your body weight or ride style and both shocks are anodized with Titanium Nitrade coating to make the stanchions harder and slicker
- Boost hub spacing widens the spoke position and improves the bracing angle to support larger plus sized tires, both the front and rear axles are thru-axles for increased stiffness and strength on rough terrain and the front offers quick release for easier trail maintenance and transport
- Massive 203 mm hydraulic disc brakes with quad-piston calipers from Magura offer efficient cooling and more powerful, controlled, stops. You can adjust the reach on each two-finger brake lever and even use them with one finger if that’s your preferred hand position
- I love that Bulls managed to squeeze in a bottle cage mounting point on the downtube, and they partnered with MonkeyLink so you can use a magnetic bottle adapter here for easier stowing vs. a cage
- It’s neat to see innovation in the lighting and fenders space, the new MonkeyLink mounts at the stem and seat post collar allow for a range of accessories that will run off the main ebike battery! my only complaint is that the headlight I saw was not aimable and thus, depends on the head tube and stem angle for direction
- The Brose powered E-Stream bikes seemed to have a lower stand over height and shorter overall length than the Bosch powered models, I think the chain stays are shorter here because of how the motor is designed, which makes for a nimble snappy ride
- To me, the rear suspension design looks a lot like split pivot, it’s designed to isolate chain movement (reducing kickback) by providing vertical play vs. horizontal and this allows for effective braking but may suffer from bob when climbing, thankfully, both shocks have compression adjust with near-lockout
- Bulls added a nicer full-surround chain guide to eliminate drops and clear debris from the chain if you’re riding in muddy or tall grass conditions
- Minor prop here, I love that the left chain stay actually has mounting holes to add a kickstand! That’s kind of rare for a full suspension electric mountain bike, but could come in handy if you commute or ride around town during the week
- The motor provides high levels of power and support almost instantly, so you can start a climb in higher gears or just get the support needed to balance right off the bat, the controller is measuring wheel speed, pedal cadence, and pedal torque rapidly
- Extra sturdy Shimano shifter levers allow for two-way action on the high gear trigger and multi-shift on the low gear lever, it’s exactly the kind of setup you’d expect from a nicer mountain bike
- Bulls has a great reputation in the US, their dealer network is expanding and the 2+ year warranty offered on this and other models appears to be well supported, shops have told me that this company is easier to work with and that has been my personal experience as well
- I like that the display panel is compact to reduce the potential for bumps and scrapes, and that there are dedicated buttons to activate lights and explore menus, it’s pretty deep for such a compact display but you have to use the joystick to navigate left/right and up/down which might not be as sturdy with lots of use compared to simple press buttons (the early Specialized Turbo models used a joystick that eventually broke for a lot of people)
- The motor kept supporting me, even when I was spinning (pedaling) very quickly at or even above 120 RPM, this was a big limitation with some of the older mid-drive systems and the takeaway is that you can simply pedal faster vs. having to shift gears to hit higher speeds in a pinch, as someone with a sensitive knee, it’s great to be able to spin faster vs. pushing harder and pedaling slower
- I had mixed experiences with the battery mount design on this bike, it seats up into the downtube and sort of just drops out when unlocked, be extra careful handling this thing because it weighs ~7.1 lbs but doesn’t have an obvious handle, it could drop out and hit the ground which could cause damage… and replacements are expensive $900+
- The battery charger is relatively large and heavy at ~2.6 lbs vs. just 1.5 or ~2 lbs, because it’s built into a tough alloy casing, the magnetic Rosenberger EnergyBus interface is cool but can pick up iron filings if set down in the dirt or sand
- The Brose S motor is extremely capable, offering up to 90 Newton meters of torque, but it does not have shift detection like Bosch or Impulse, so you want to ease off when changing gears so you don’t mash and bend your sprocket teeth
- I struggled to figure out how to switch from km/h to mph in the Marquardt display, it might be something that is setup at the factory and not open to adjustment? I was not able to experiment with the app but perhaps that adds some additional features
- The display is a bit bright, in terms of backlighting, it only shows four bars for battery level (five, ten, or a percentage would be more useful), and the range estimate isn’t as dynamic as Bosch and some other companies where it gives you an range for each level of assist
- By default, the seat post dropper lever is mounted near the left grip, and it sort of gets in the way of the display panel (which is mounted just to the side of it), I’m not sure how to overcome this because the dropper lever would be really tough to reach if it was setup behind the display, maybe putting it on the right portion of the handlebar vs. the left?