BULLS have finally joined the light eMTB game with the SONIC EVO AM SX-I. In our 2024 e-mountainbike group test, it takes on the competition with a Bosch Performance Line SX motor, 29” wheels and 140/130 mm of travel. The SONIC EVO AM SX-I is aimed primarily at sporty riders with a penchant for trail riding. How did the German lightweight fare against the other 26 competitors in our 2024 comparison test?

BULLS SONIC EVO AM SX-I | Bosch Performance Line SX/400 Wh | 140/130 mm (f/r)
18.6 kg in size L | € 9,999 | Manufacturer’s website

BULLS entered our 2024 e-mountainbike comparison test with not one, but two bikes: the VUCA EVO AM and SONIC EVO AM SX-I. However, the concepts couldn’t be more different from each other, at least visually. The VUCA EVO AM relies on a beefy frame with a menacing enduro look, all topped off with a Pinion motor system. The SONIC EVO AM SX-I, on the other hand, is based on a lightweight concept, boasting a more discreet, sleek look. Although the AM acronym stands for “all mountain”, BULLS’ new light eMTB was designed more for sporty tours with occasional trail detours, rather than rowdy trail sessions. The SONIC EVO AM SX-I rolls on 29” wheels and generates 140/130 mm of travel (f/r), which makes it the bike with least travel in our 2024 e-mountainbike comparison test. The SONIC comes equipped with a Bosch Performance Line SX motor that delivers 55 Nm of torque, and draws its power from a 400 Wh battery. Our test bike retails at € 9,999 and tips the scales at 18.6 kg, which is average in our light e-MTB test field. In addition to its sporting ambitions, it should also impress with clever everyday features. We tested the BULLS SONIC EVO AM SX-I to see how it fares against the competition, both on and off the trails.

For an overview of the test fleet head to the group test: The best eMTB of 2024 – 27 of the most exciting models in our comparison test

Silver Arrow – What sets the BULLS SONIC EVO AM SX I apart from the competition?

Although some motorsport historians might disagree, legend has it that the iconic “Mercedes Silver Arrows” name originated in the early 1930s, when the Mercedes team decided to remove all the paint from the bodywork to meet the weight limitations. With the SONIC EVO SX-I, the BULLS team seems to have followed suit, both by keeping the weight down and replicating the legendary Silver Arrows look. With its rectilinear, square-edged silhouette, the full carbon frame looks elegant and subtle, which is topped off by a two-tone paint finish with matt black and silver accents – it’s just missing the race plate! The cables are routed internally and disappear neatly into the frame through conventional cable ports, ensuring a tidy look, and going against the current trend of internal headset routing. To minimise pit stops on the way, the BULLS team added 5 mounting points to the underside of the top tube, allowing you to attach a tool strap for basic trailside repairs, as well as a bottle cage for optimal hydration. There’s also a MonkeyLink Connect mount under the stem, which serves as a universal interface for several MonkeyLink headlights, meaning that you won’t be left in the dark when a ride is longer than expected. The headlight mount is complemented by MonkeyLink TwinLights at the rear, which come as standard with the bike and ensure excellent visibility. The rear lights are neatly integrated into the frame, tucked away seamlessly into the seat stays. Both the front and rear light draw their power directly from the main battery.

The Silver Arrow comes equipped with a Bosch Performance Line SX motor, which delivers 55 Nm of torque and 600 watts peak power.
The 400 Wh battery can be removed from the side of the frame and is secured with a key lock.
There are 5 mounting points for bottle cages and range extenders on the underside of the top tube, meaning that you can keep hydrated and carry all your trail essentials directly on the bike.

The spec of the BULLS SONIC EVO AM SX-I also suits the Silver Arrows theme! Generating 140 mm of travel, the silver RockShox Pike Ultimate matches the bike’s colour scheme and offers countless adjustment options, while at the same time delivering a tremendous performance on the trail. The slim, black RockShox Deluxe Ultimate air shock forgoes a piggyback reservoir, matching perfectly with the overall discreet look of the bike while at the same time helping to save weight. To round off the light eMTB concept and match the fork, BULLS chose TRP’s silver C2.3 four-piston brakes, which are pretty rare to see around and are only featured on one bike in this test. The brakes are paired with 203 mm rotors front and rear, providing sufficient braking torque. However, some of our test riders didn’t get along with the brake’s ergonomics, because the levers move in an arc rather than drawing a linear path. This leads to a slight pressure on your fingers when you pull hard on the lever. The Limotec Alpha 1UH dropper post offers 150 mm of travel, which isn’t enough for a bike in size L. The electronic SRAM XX Eagle AXS Transmission drivetrain ensures smooth gear shifts and relies on a hanger-less rear derailleur, which is extremely robust, and bolts directly to the frame. For the wheels, BULLS rely on a MAVIC E-Crossmax SL carbon wheelset and lightweight Schwalbe tires, combining a Nobby Nic at the front and Wicked Will at the rear, and thus proving clearly that weight and efficiency are high on their priority list. Both tires come in the thin SuperRace casing and hard Speedgrip compound, which, as their name clearly suggest, were designed with rolling efficiency and lightweight in mind. If you spend lots of time on technical trails and want to protect the expensive carbon rims, we recommend upgrading to more robust tires with the tougher SuperTrail casing.

The MonkeyLink TwinLights ensure good visibility and are seamlessly integrated into the frame, drawing their power directly from the main battery – awesome!
Both Schwalbe tires come in the thin SuperRace casing and hard Speedgrip rubber compound. For more trail performance, we recommend upgrading to the more robust SuperTrail casing and a softer rubber compound.

What would a Silver Arrow be without a motor? The BULLS SONIC EVO AM SX-I relies on a Bosch Performance Line SX motor, which is the most powerful light eMTB drive system in this test, delivering 55 Nm of torque and 600 watts peak power. Although seamlessly integrated into the frame, the motor is slightly bigger than its direct competitors, the TQ, FAZUA and maxon, which is clearly visible at first glance. The motor draws its power from a 400 Wh battery, which can be easily removed from the side of the frame, and is secured by a key lock, like the KTM’s battery. Incidentally, these are the only two light eMTBs with a removable battery. For long-distance races and epic backcountry expeditions, you can expand the battery with an optional 250 Wh range extender, which can be secured to the underside of the top tube and connected to the charging port at the top of the down tube. BULLS went for a minimalist cockpit with the SONIC EVO AM SX-I, combining a Bosch System Controller in the top tube and Mini Remote on the handlebars. Both are reduced to the bare essentials, and impress with good haptic feel and ergonomics.


€ 9,999


Motor Bosch Performance Line SX 55 Nm
Battery Bosch CompactTube 400 Wh
Display Bosch System Controller
Fork RockShox Pike Ultimate 140 mm
Rear Shock RockShox Deluxe Ulitmate 130 mm
Seatpost Limotec Alpha 1UH 150 mm
Brakes TRP C2.3 RX 203/203 mm
Drivetrain SRAM XX Eagle AXS Transmission 1x12
Stem BULLS 50 mm
Handlebar BULLS riserbar 780 mm
Wheelset Mavic Crossmax XL R 29 29"
Tires Schwalbe Nobby Nic SuperRace, Speedgrip/ Schwalbe Wicked Will SuperRace, Speedgrip 2.4/2.4

Technical Data

Size S M L XL
Weight 18.6 kg
Perm. total weight 130 kg
Max. payload (rider/equipment) 111 kg
Trailer approval no
Kickstand mount no

Specific Features

MonkeyLink lighting system with rear light

Tuning tip: If you want to test the limits of your heart rate and squeeze the last ounce of performance out of the BULLS, upgrade to tires with a more aggressive profile and robust casing.

What is the BULLS SONIC EVO AM SX-I capable of on the trail?

Just like a racing car, the BULLS SONIC EVO AM SX-I places you in a sporty, stretched position that pushes your upper body far forward. On level ground and fire roads, this position puts a slight pressure on your hands, though this vanishes as soon as the gradient increases. With its firm suspension and shallow-profiled tires, the SONIC EVO AM SX-I is efficient on flat trails and needs little input from the rider to get up to speed. The Bosch Performance Line SX motor requires high pedalling cadences to fully develop its power, which fits in perfectly with the bike’s sporty orientation. Nevertheless, the motor pushes significantly harder than the TQ-HPR50, FAZUA Ride 60 or Specialized SL1.2. Experienced riders with a good level of fitness can even keep up with the full-fat competitors in this test. As soon as the climb gets steep and technical, the suspension/tire combo reaches its limits and struggles to generate traction.

On technical climbs, the firm suspension and shallow-profiled tires quickly reach their limits and generate little traction.
On flowing trails, the firm suspension allows you to generate plenty of speed by pumping through rollers and berms.

When gravity takes over, the BULLS integrates you nicely between its wheels, while the front-heavy riding position helps you squeeze every ounce of traction out of the shallow-profiled tire in open corners, without having to actively weight the front wheel. On flowing trails, the BULLS impresses with intuitive handling, and the firm suspension allows you to generate plenty of speed by pumping through rollers and berms, while at the same time providing enough reserves for bigger jumps. When ploughing through small root carpets and isolated rocks, the suspension effectively absorbs impacts, providing less feedback than the CENTURION No Pogo SL R8000i. Overall, the suspension seems to have more travel than it says on the tin, encouraging even beginners to open the gas. While on moderate trails the BULLS is plenty of fun with its direct, intuitive handling, on rougher trails it reaches its limits, requiring good skills and a vigilant riding style to negotiate rock gardens and steep off-camber sections. For experienced riders, the agile handling makes it easy to spontaneously change lines and provides plenty of riding fun in challenging terrain. If you want to treat yourself to an ice-cold brew after a long day in the saddle, you can shut off the motor using the Bosch eBike Lock.

With its agile handling, the BULLS SONIC EVO AM SX-I feels at home on flowing trails, but requires an experienced rider on demanding terrain.

Size S M L XL
Top tube 580 mm 620 mm 640 mm 663 mm
Seat tube 400 mm 440 mm 470 mm 510 mm
Head tube 100 mm 110 mm 130 mm 140 mm
Head angle 65.5° 65.5° 65.5° 65.5°
Seat angle 75.0° 75.0° 75.0° 75.0°
Chainstay 450 mm 450 mm 450 mm 450 mm
BB Drop 38 mm 38 mm 38 mm 38 mm
Wheelbase 1,184 mm 1,218 mm 1,246 mm 1,270 mm
Reach 420 mm 450 mm 470 mm 490 mm
Stack 624 mm 633 mm 650 mm 669 mm
Helmet Sweet Protection Trailblazer | Glasses NAKED Optics The VOLT | Hip Pack EVOC HIP PACK 3
Jersey POC MTB Pure | Pants ION MTB Tech Logo | Shoes Five Ten Freerider Pro
Socks FOX Ranger Sock | Gloves Prologo Energrip

Who should take a closer look at the BULLS SONIC EVO AM SX-I and who should look elsewhere?

Despite having many practical features for the daily commute, like the MonkeyLink TwinLights, the BULLS SONIC EVO AM SX-I is definitely a bike for e-riders with sporty ambitions. The stretched riding position, small battery and weaker motor make it suitable for shorter, fast-paced rides. While it’s still plenty of fun for beginners on moderate trails, it requires an experienced hand as the trails get more challenging.

Riding Characteristics


  1. unbalanced
  2. coherent


  1. cumbersome
  2. clever


  1. flop
  2. top


  1. low
  2. high


  1. demanding
  2. intuitive


  1. boring
  2. lively

Intended Use

Gravel roads

Technical climbs

Flowtrail descents

Technical descents

Our conclusion about the BULLS SONIC EVO AM SX-I

The new BULLS SONIC EVO AM SX-I comes with a stylish Silver Arrows look and clever everyday features like the integrated lights. With its agile character, the German lightweight feels at home on flowing, moderate trails, but quickly reaches its limits on technical terrain. Uphill, it performs better on fast fire roads than technical climbs. Overall, the BULLS covers a rather limited range of applications, thus falling behind the more versatile all-rounders in this test.


  • Clean look
  • Clever everyday features
  • Agile handling on flowing trails


  • Tires quickly reach their limits on the trail
  • Handling can get overwhelming on technical terrain

For more information, visit bulls.de

The test field

For an overview of the test fleet head to the group test: The best eMTB of 2024 – 27 of the most exciting models in our comparison test

All bikes in test: BULLS VUCA EVO AM 2 (Click for review) | BULLS SONIC EVO AM SX-I | Canyon Strive:ON CFR LTD (Click for review) | Canyon Torque:ON CF Roczen (Click for review) | CENTURION No Pogo SL R8000i (Click for review) | CUBE AMS Hybrid ONE44 (Click for review) | FLYER Uproc X 8.70 (Click for review) | FOCUS SAM² 6.9 (Click for review) | GASGAS ECC 6 (Click for review) | GIANT Trance X Advanced E+ Elite 0 (Click for review) | KTM Macina Scarp SX Prime (Click for review) | Lapierre Overvolt GLP3 (Click for review) | Merida eOne-Sixty 10K (Click for review) | Mondraker Neat RR SL (Click for review) | Moustache Samedi 29 Game 11 FOX (Click for review) | Orbea WILD M-LTD (Click for review) | Pivot Shuttle AM Team (Click for review) | Propain Ekano 2 CF (Click for review) | RADON RENDER 10.0 HD (Click for review) | ROTWILD R.X 1000 Ultra (Click for review) | Santa Cruz Heckler SL XX AXS RSV (Click for review) | SCOR 4060 ST (Click for review) | SCOTT Voltage eRide 900 Tuned (Click for review) | SIMPLON Rapcon Pmax Pinion (Click for review) | Specialized Turbo Levo SL Expert (Click for review) | Specialized Turbo Levo Pro (Click for review) | Spherik E-SMT XX AXS (Click for review)

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Words & Photos: Mike Hunger

About the author

Mike Hunger

From slopestyle and landscape photography to enduro and action shots. Mike enjoys trying new things and loves action. He also loves craftsmanship, regularly going on road trips with his VW Syncro van, which he restored and converted himself. Of course, his bike and his camera are always with him so that he can ride the finest trails from Italy to the Alps and capture the most beautiful moments. Thanks to his training as an industrial mechanic, his experience in cycling and his photographic skills, he can apply his know-how perfectly as a bike journalist, testing the latest bikes and components and documenting his findings. As a photography nerd, he also captures the reviews with his camera and ensures that the magazine features only the best images.