2019 BULLS SIX50 EVO AM 4 Review


Technical Specs & Ratings





Class 1


Full Suspension



Hydraulic Disc



482.4 Wh

482.4 Wh

54.4 lbs / 24.70 kgs



Frame Details

7005 Aluminium Alloy


Full Suspension


Fox Float Factory with Dual Piston System (DPS) Air Suspension, 150 mm Travel, Compression Adjust (1,2,3), Rebound Adjust, Boost 148 mm Hub Spacing, 12 mm Thru-Axle with 6 mm Hex Bolts

Fox Float Factory 36 Air Suspension with Kashima Coat, 150 mm Travel, Compression Adjust (Open, Medium, Firm), Rebound Adjust, Boost 110 mm Hub Spacing, 15 mm Thru-Axle with Quick Release

DT Swiss H 1700 SPLINE, Double Wall, Alloy, 35 mm Inner Width, 32 Hole | Spokes: Stainless Steel, 14 Gauge, Straight Pull, Black with Nipples

Schwalbe Magic Mary, 27.5" x 2.6" (65-584), 17 to 35 PSI, 1.2 to 2.6 BAR, ADDIX Speedgrip, EVO Evolution, APX Reinforced, TLE Snakeskin


FSA Orbit 1.5 ZS, Sealed Cartridge, Threadless, Internal Cups, Tapered 1-1/8" to 1-1/2"

MonkeyLink Mangnetic Interface, Alloy, 55 mm Length, 0-Degree Rise, Two 10 mm Spacer, One 5 mm Spacer

Bulls Branded, Alloy, Low-Rise, 760 mm Length, 15 mm Rise, 9-Degree Bend, 31.8 mm Bore

Ergon GD1 Factory Frozen, Flat Rubber, Locking

Kind Shock Lev SI Dropper (100 mm, 125 mm, or 150 mm Travel)


Fizik Gobi M7

Wellgo ZZE-01M Alloy Platform, Cage Style

Hydraulic Disc

Magura MT7 Hydraulic Disc with 203 mm Rotor in Front and 180 mm Rotor in Back, Quad-Piston Calipers, Two-Finger MT7 CARBOTeCTURe Levers with Shiftmix 3 Clamp and Tool-Free Reach Adjustment and Tool Free Free Stroke Adjustment

More Details


2 Years Motor and Battery, 5 Years Frame

United States, Canada


17.32, 19.29, 21.25

Medium 49 cm Measurements: 19.5" Seat Tube, 23.5" Reach, 31" Stand Over Height, 37" Minimum Saddle Height, 31.25" Width, 77.5" Length

Silver with Matt Black and Orange Accents

MonkeyLink Magnetic MonkeyBottle Mount on Downtube

Magura MT7 Hydraulic Disc with 203 mm Rotor in Front and 180 mm Rotor in Back, Quad-Piston Calipers, Two-Finger MT7 CARBOTeCTURe Levers with Shiftmix 3 Clamp and Tool-Free Reach Adjustment and Tool Free Free Stroke Adjustment

Video Reviews

Written Reviews

To run the forums, host the website, and travel, I charge a universal service fee for my reviews. This in-depth review was sponsored by BULLS North America. My goal is to be transparent and unbiased, this video and written review are not meant to be an endorsement of BULLS products.

The BULLS SIX50 EVO AM 4 is an all-mountain electric bike running the proven Bosch CX motor and frame-integrated Bosch PowerPack 500. It’s well balanced and sturdy, featuring wider Boost hub spacing, thru-axles, and plus sized Schwalbe Magic Mary tires that reduce deflection, improve traction, and provide float for the heavier bike. Compared to the 2018 model, which used a Shimano drivetrain, the 2019 SIX50 EVO 4 SRAM is actually two pounds lighter, but still comes in at roughly 54.4lbs. Aside from the Fox Factory shocks, Magura MT7 hydraulic disc brakes with carbon fiber levers, SRAM EAGLE X11 12-speed drivetrain, and PowerTube batttery, one of the things that really differentiates this model from other leading products for 2019 is the color Bosch Kiox display panel. It’s exciting to see and experience the latest and greatest ebike hardware from a leading brand with a growing network of shops in North America. Bulls has been selling in the USA since 2016 and their independent bicycle dealers provide ongoing service and warranty support. The SIX50 EVO AM 4 comes in three frame sizes, which are great to experience in person, and you’ll notice the sloped top tube for more comfortable standover. Furthermore, I really appreciate dropper seat posts that don’t have pre-set positions. The Kind Shock LEV SI dropper comes in three lengths to accommodate the three different frame sizes. Also, while many competing full suspension ebikes struggle to fit on bottle cage bosses, BULLS has gone above and beyond with the magnetic MonkeyLink downtube mount and two wired-in MonkeyLink light interfaces. The stem and seat post clamp work with a whole range of accessories, including a rear fender option. The headlight design is not aimable and the dual-light pack costs $170, which is a bit high in my opinion, but they’re very functional and easy to remove for weight savings if you know you’ll be back before the sun goes down. In short, you’re getting an extremely rugged, capable, and beautiful electric bike here. Bulls offers a specced-down model called the EVO AM 3 for people who want to save some coin and are okay with RockShox suspension and a Shimano XT drivetrain. I actually prefer the trigger shifters from Shimano because the high lever moves in both directions (forward or back), and the low lever can do multi shifting. Shimano also offers a one-way clutch feature on their derailleur… which is what we saw with the 2018 SIX50 EVO AM 4, it had Shimano XTR. SRAM has their own roller clutch feature to make rear wheel maintenance easier, and the derailleur shifts quick and clean, I’m just more used to Shimano. Anyway, the EVO AM 3 uses the same battery setup and motor as the AM 4 but comes in dark grey and neon green vs. the exposed silver Aluminum here.

Driving this ebike is a powerful mid-motor from Bosch called the Performance Line CX. It offers 350 to 570 watts of power output, and up to 75 Newton meters of torque depending on the level of assist being used. If you live in Europe, this system may be rated at 250 to 500 watts and limited to 25 km/h vs. 20 mph (32 km/h), but it still delivers high torque. The motor controller listens to rear wheel speed using a magnet and electronic sensor on the left chain stay, pedal cadence, and pedal torque signals, over 1,000 times per second. These signals allow it to start and stop almost instantly to keep you in control… which is especially important in a technical mountain setting. Beyond assistance, this motor controller is also listening for tension changes in the chain, resulting from gear shifting. When it senses these inputs, it tells the motor to ease off in order to reduce mashing and gear grinding. It’s not a perfect system, and you can help it by reducing force on the pedals yourself as you shift gears, but it’s something that only Bosch is really doing right now. There have been a few hardware driven shift detection designs over the years (from Impulse and Bafang partners) but the software solution that Bosch has developed is a real differentiator. I love how BULLS has angled the motor and tucked it up into the frame in order to maximize ground clearance and shorten the effective chain stay length for a snapper ride feel. Visually, the motor doesn’t blend into the frame as nicely as if it had a silver casing, but the neon orange aluminum skid plate does set off the fork sticker and label accents around the frame and tires. This motor spins a single chainring with 16 teeth (one more than the 15t chainring on the 2018 model), to maximize starting and climbing power while allowing for high top speeds. It balances the wider 11 to 50 tooth cassette perfectly and is roughly equivalent to a traditional 40 tooth chainring. The chainring spins at 2.5 revolutions for each crank revolution because the motor has a reduction gear to provide a mechanical advantage. I’m told that the smaller chainring increases chain grab but noticed that it can also bring the chain closer to the right chain stay and possibly allow for chain suck in very muddy environments. The Bosch Performance Line CX mid-drive unit is also the most power hungry and loudest of the Bosch lineup and it weighs a bit more at 8.8lbs. But again, that weight is positioned very low and centered along with the battery pack for optimal balance and stability. Expect reliability, great power, dynamic ride experiences with eMTB mode, and an increase in noise at high pedal rates. All Bosch Performance Line motors support pedal rates up to 120 RPM, which allow them to continue supporting you during massive downshifting, riding into a steep hill. For even more details and footage, check out my stand alone Bosch CX motor review in the EBR forums.

Powering the bike is a high capacity Bosch PowerTube 500 battery which offers 36 volts and 13.4 amp hours for a total of 482.4 watt hours. Bosch has been supplying ebike batteries to North America since 2013 and is well known for reliability and cross compatibility between different brands. That’s less common now with the PowerTube, because there is a vertical mount and side mount option, and each manufacturer can opt for a custom interface and cover. BULLS has chosen a bottom-load design that’s easy to click in without needing a key but can be a little tricky to remove… their aluminum alloy covers look great, but add nearly a pound of weight and are color-matched so don’t look good if you swap between different bike models. As for the PowerTube battery, there’s no carry loop at the top or side, which means you have to use extra care connecting and disconnecting it from the frame. Iit still has a 5-LED battery indicator on the end (near the charging port) so you can quickly judge capacity even if you store it separately from the bike frame. I almost always take the pack off before lifting the bike for service or transport. The charging port of the battery is replicated on the left side of the bike frame, near the base of the downtube, so you can charge without removing the battery every time. The thing is, this port is located very near the left crank arm and I could imagine a snag or disconnect if you’re charging and bump the pedals… it also seemed like the protective rubber cap for this port didn’t seat as easily as some competing designs. The PowerTube battery pack requires a bit of extra flexibility and patience to remove from the frame. First, you have to insert the key and unlock it, then the pack sort of pops out (downwards) half an inch near the head tube. At this, point the pack is unlocked but it won’t come out completely. To fully release it, you have to press a little plastic button inside the crack, all while trying to balance the bike frame because there’s no kickstand. The left chain stay actually does have a 20mm kickstand mounting point if you wish to use it, but a stand would add weight rattle a round constantly in rough terrain. Anyway, I have relatively small fingers, so it wasn’t too difficult to remove the pack. Once you actually press the button, the pack is completely free at the top and will swing down towards the front tire. It weighs about 7.2lbs total, with the attached metal shield, so expect a bit of weight and please be careful not to drop the battery because they are like $900 to replace. Again, the PowerTube battery for BULLS doesn’t have a handle built in, and with the metal shield it weighs more than the older Powerpack… and, since it’s coming down vs. resting as you lift up, it just seems more precarious. Perhaps that is why Bosch encased the PowerTube itself in an Aluminum alloy box. As a side note, to best care for the lithium-ion cells that are packed inside the PowerTube, I have heard that you should avoid storing it in extreme heat or cold, and that you should leave it around 50% full for long periods of disuse vs. completely full or empty. Charging the pack is fast and easy with the included 4 amp Bosch charger. It is one of my favorite chargers because it is so compact and lightweight at ~1.7 lbs. You will probably have better luck sticking this charger into a backpack than trying to bring along a second PowerTube battery to extend range. Bosch does offer a compact travel charger that delivers 2 amps, but it’s only 0.5lbs lighter and just a little bit slimmer, so I’d probably just stick with the original. In conclusion, I feel that the PowerTube battery offers a mixed bag of benefits and trade-offs. It’s hidden, positioned low, doesn’t rattle, and offers a relatively high capacity, but is heavy and less easy to swap and use with a second pack because of the screwed-on shield design. For even more details and footage, check out my Bosch PowerTube review in the EBR forums.

One of the most noticeable changes for 2019 is the Bosch Kiox display panel vs. the Bosch Purion. This thing has a color LCD, Gorilla glass screen, active Micro-USB charging port, connects via magnets and is removable, but cannot be adjusted for glare because it mounts in a fixed position over the stem. In terms of actual use, the Kiox provides more detailed menu readouts; including 1% stepped battery percentage vs. a five-bar infographic with wider 20% steps. Its color readout provides a fast and comfortable way to interpret assist levels (grey for Off, blue for Eco, green for Tour, yellow/gold for Sport or eMTb, and red for Turbo). The screen on the Kiox is smaller than Intuvia, but the colors make it easier to interpret in many ways without having to squint and actually read. Because of how it’s mounted, my guess is that the Kiox may also take less damage if the bike tips or crashes. I think it’s actually designed to pop off vs. cracking the mounting bracket when taking direct hits. Interacting with the display involves some button clicking. You begin by charging and mounting the battery, then press the power button on the display unit. The Kiox has power and lights buttons positioned juste below the screen. Most interactions are done through a remote button pad which is mounted within reach of the left grip. This pad has a +, -, left, right, and select button, along with a walk mode button on the top edge. It boots up in the second view, showing your assist level with a swirling color infographic. different parts of the swirl line fill based on how much power you exert as a rider and how much power the motor exerts, when active. You can arrow left or right to change screen readouts, and I especially like the ones towards the right, which show a range estimate based on remaining battery capacity and the last mile of riding. Unfortunately, the Kiox requires you to click right or left to get through, and does not loop back to the start for convenience… and this requires more hand effort and time. Perhaps Bosch will update this in the future, because the Kiox does come with Bluetooth integration and will be able to connect to a smartphone app. For now, Bluetooth seems to be reserved for use with aftermarket heart rate monitors. I’m reviewing this product in North America, but Europe is a bit ahead with the release and apps. The two markets differ slightly and I’d recommend working with your local dealer to learn more and get help with software updates. Okay, all things considered, the Kiox is an excellent display units. It brings a lot of improvements over Purion and Intuvia while adding a touch to the price point. For more information and pictures of the Kiox, I’ve created a guide in the EBR forums here.

In closing, the SIX50 EVO AM 4 is a top-end enduro electric mountain bike with excellent suspension and some welcome refinements for 2019. I appreciate that they switched to ABUS locking core for the battery, because it comes with a keyed-alike card that lets you order matching lock accessories. The new Kiox display takes the compact size and durability of the Purion with the removability and functional Micro-USB charging port and deeper feedback of Intuvia. The new Magura MT7 brake levers offer tool free reach and throw adjust, which is something I rarely see, and the rear caliper now offers quad piston vs. dual piston before. This electric bike is comfortable, responsive, highly adjustable (with rebound, compression, and sag adjust on the shocks), and all of the suspension stanchions are anodized with the Fox Kashima coating to slide smoothly and be tough. I even like the grips that were chosen, but the Fizik saddle is a little round and hard for my taste and the pedals are just basic cages that can easily get bent and become sharp… so I’d replace those. As always, I welcome corrections and feedback in the comment section below and welcome you to post your own reviews, pictures, and make friends in the Bulls Ebike forums.


  • Totally custom frame with sleek motor integration to maximize ground clearance, hidden battery and integrated wires, three frame sizes to choose from so you can dial in fit and comfort (I reviewed the Medium 49cm)
  • The sloped top tube is designed to lower standover height and help you step off without racking yourself if the terrain is unstable or soft
  • Top-of-the-line suspension from Fox, the 150mm travel length is ideal for Trail and All-Mountain riding, wider 36mm suspension fork stanchions provide stiffness and strength to the fork which is important given the thicker 15mm thru-axle with wider Boost hub spacing and heavier plus sized tires, both shocks offer, rebound, compression (climb, trail, descend), and air pressure adjustments for different body weights and terrain
  • Boost hub spacing also provides a stronger bracing angle for the spokes, both wheels attach with sturdy thru-axles and the rims and tires come tubeless ready for easy conversion to save weight and ride with lower PSI
  • The suspension design resembles split-pivot which is great for isolating vertical movement and reducing chain kickback, it brakes well but suffers a bit from bob during climbs (so the compression adjustment on the rear shock is nice to have)
  • The frame comes stock with MonkeyLink light and fender attachment points, if you add lights to the stem and seat post clamp they will run off of the main battery pack which is convenient… the lights are quick and easy to remove to reduce weight and clutter if you’re not expecting to ride in the dark
  • I love the magnetic MonkeyLink bottle cage adapter on the downtube, it’s great to have fluids within reach and many competing electric mountain bikes (especially full suspension models) just don’t have room for this type of thing, for those who aren’t thrilled with the $46 bottle accessory, you can remove the magnetic dock and mount standard aftermarket parts (cages, folding lock, mini-pump etc.)
  • Great seat post dropper from Kind Shock, it comes in several lengths to match the bike frame size and allows you to adjust the height wherever you want vs. set intervals, I feel like this sort of accessory has become standard on higher priced all mountain and enduro electric bikes
  • Upgraded SRAM Eagle 12-speed drivetrain with enormous 11-50 tooth cassette vs. the older SIX50 EVO model which came with Shimano XTR 11-46 tooth cassette
  • Premium Magura MT7 hydraulic disc brakes with large 203mm front rotor offering leverage and cooling benefits, quad piston calipers provide maximum grab, CARBOTeCTURe levers reduce weight and offer adjustable reach and throw for different hand sizes and gloves vs. no gloves
  • I really like the Ergon GD1 Factory Frozen grips used on this bike and haven’t seen them on many other models, they are locking, have a rubber inner guard, a semi-ergonomic design, and rounded vs. flat for comfortable use with mountain biking gloves
  • The high volume Schwalbe Magic Mary tires offer excellent traction, reduced deflection off of rocks, float in soft terrain, and they are rated EVOLUTION which means “the very best possible made with high grade materials and the latest technology” you get TLE tubeless easy, and sturdy APX reinforced sidewalls
  • BULLS has added a little alloy guard to reduce pant leg contact with the chain and chainring, I love how compact they managed to make their motor casing, and appreciate the color matching and tough skid-plate below, there’s also a little shield protecting the stanchion on the rear shock so it won’t get dirty and chipped up over time
  • As with most high-end electric bicycles, all of the cables and wires are internally routed through the frame here, it looks nice and reduces the potential for snags
  • The frame comes with kickstand provisions towards the back of the left chain stay, if you do add one for urban riding, it shouldn’t get in the way while pedaling and won’t cause pedal lock, BULLS uses the Standwell SW-RA032J on their urban models like the ICONIC EVO TR 1
  • BULLS chose to build their battery lock design with an ABUS locking core, and they come with a little card that has a code on it so you can order matching locks and other accessories, this is a unique program that could help you reduce clutter on your keychain and order replacement keys more easily
  • Given the high-capacity Bosch PowerTube 500 battery, it’s nice that BULLS opted to include the faster four amp charger, it’s relatively lightweight at ~1.7lbs and fairly compact, so you can bring it along on rides to top off when taking a break
  • With the Bosch Performance Line CX motor you get access to very high torque output, up to 75 newton meters, and eMTB drive mode which dynamically responds to your pedaling for low and high power output without having to interact with the display, it’s based more on torque and was developed with input from pro mountain bike riders by Bosch, it works pretty well and feels natural
  • The Bosch motor controller is extremely smart and consistent, it measures rear wheel speed, pedal cadence, and pedal torque over 1,000 per second while also listening for pressure changes from shifting and then easing off, this protects the drivetrain a bit from mashing
  • Another great feature with Bosch Performance Line motors is that they can support higher pedal rates without fading out and losing power, you can reach 120 RPM (pedal strokes per minute) and the motor will still be there for you, this allows you to downshift when going into a hill without losing support
  • With all of the Bosch motors, there’s a shift detection software system built in that can sense that gears are being changed and it tries to ease off of the power to reduce strain on the drivetrain, it’s not perfect but it’s better than nothing and really comes in handy with a 12 speed drivetrain!
  • The bike has walk mode enabled, which is especially useful if you encounter a section of road or trail that you aren’t comfortable riding or maybe you get a flat tire, considering that the bike weighs ~60 lbs and has pannier racks for cargo, it could be really nice to get help moving it along in some situations
  • Battery and motor weight are kept low and center on the frame which improves stability and handling, with the main triangle section open on this electric bike, you can more easily lift it and hang it from some car and bus racks
  • The battery pack can be charged on or off the bike frame (for convenience, battery protection, and reduced weight for transport), I recommend storing lithium-ion battery packs in a cool dry location to keep the cells healthy, try not to store it below 50% over long periods
  • Unlike some other Bosch PowerTube battery implementations, this one can be forced into place without using the key to unlock the core, just push on it and listen for a click to know that it’s securely mounted
  • Not every electric bicycle company has mastered the design aesthetic of integrating the Bosch motor as well as BULLS has, in my opinion, look at how it’s angled up and incorporated into the seat tube and downtube to raise ground clearance, it really blends in compared to the big plastic housing used by many other companies
  • Interacting with the display is intuitive and simple enough that you really don’t have to look down that often once you get the hang of it, the button pad is positioned within reach of the left grip and produces a tactile click
  • I love that Kiox is color because it’s easy to interpret which assist level you’re in without squinting to read a small font, I love that it lists battery percentage in addition to range estimate for more precise trip planning, and I love that Bosch is working on Bluetooth applications which could sync with heart rate monitors and other devices in the future
  • The Kiox display is well protected at the center of the bar, is connected via magnets and can be removed easily, uses Gorilla Glass so it won’t scratch up like plastic, and it offers Micro-USB charging for portable electronics
  • Excellent two year warranty covers everything on the bike, including the motor, battery, and display system with a vast network of dealers in the US and other parts of the world who can help with fit and maintenance


  • This ebike is on the heavy side at 54.4lbs because it has wider Boost hub spacing, sturdy thru-axles, high volume tires, and the heavier Bosch PowerTube battery with alloy casing… but at least you can remove the battery to reduce that weight by roughly 7.2lbs and the front wheel has quick release, it’s actually ~2lbs lighter than the older SIX50 EVO because of the carbon brake levers, SRAM drivetrain, and other refinements
  • As with any premium electric bike with name brand components and a leading drive system that is custom-integrated into the frame, this ebike costs more money, but at least it is sold through dealers who can offer support and comes with a great 2+ year comprehensive warranty
  • The Bosch CX motor is responsive and powerful but also draws energy faster, produces more noise, and weighs a bit more than competing products like the Shimano STePs E8000 or Yamaha mid-drive
  • The Bosch Performance Line motors are heavier and larger than the Brose S, Shimano E8000, and Yamaha PW-X while also having a wider minimum Q-Factor (so the bottom bracket can be wider), but that’s not a huge issue given the wider Boost hub spacing and larger tires on this ebike
  • Because the motor uses reduction gearing system with a smaller 15 tooth chainring (which spins 2.5 revolutions for each crank revolution), you end up with some friction if the motor isn’t assisting, this adds just a touch of work… but the upside is that the smaller sprocket grabs the chain well and offers a mechanical advantage tot he motor
  • Minor gripe here, the front MonkeyLink connection point is fixed, so you cannot adjust the angle of the headlight as you can with many competing bolt-on lights from Busch & Müller, Supernova, Fuxon and others
  • The Powertube battery is not available in a smaller 400 watt hour configuration (that could reduce weight and cost less as a spare), it may be difficult to rent on location or to carry separately because of the long dimensions and extra shielding piece, it seems like you’d have to unscrew that from the original pack and re-attach to work with a second battery… it’s just not nearly as versatile as the older PowerPack batteries
  • The location of the battery charging port on the left side of the bike frame is pretty close to the left crank arm, and actually blocks the rotation path when plugged in, just be careful not to bump the pedals when the bike is plugged in, or consider charging the battery off the bike, the rubber cover protector for this port is also a bit finicky to get in (at least for me)
  • I’m not a huge fan of cage pedals like the ones included with the BULLS SIX50 EVO AM 4 because they don’t offer a lot of surface area and can easily bend and become sharp when laying the bike down on its side, consider swapping for some Wellgo alloy or magnesium platform pedals if you’re concerned about slipping off or have larger feet
  • I don’t like the SRAM trigger shifters as much as Shimano because they only offer a single step vs. multi-shift and both levers only go forward vs. two-way on the high lever from Shimano

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