Bulls Sonic Evo AM SL in Review

The Bulls Sonic Evo AM SL 3 combines features that no manufacturer has managed to combine so far. The bike has a powerful motor, a 725 Wh battery, and still weighs under 21 kg. Is there a catch to the overall package?

When comparing the facts, similar offers on the market are found only above the 10,000 € mark. Bulls demonstrates skill in the construction and specification of the bike. Our standardized Price/Performance Check, which we apply to all bikes on the market, strikingly leans towards “excellent” here.

A key to the excellent weight is certainly in the frame. The main carbon frame is complemented not only by a carbon rear triangle, but even the rocker link is made of carbon. Even the battery has a carbon casing. Bulls really went all out here.

And the components make no mistakes on the scale either. A reliable four-piston braking system, a capable suspension, and lightweight, durable wheels. The entire wheelset including tires, rotors, and cassette weighs only 4680 grams. That’s really light. However, it’s clear: With only 140 mm of travel and Schwalbe’s Nobby Nic tires, the range of use is not designed for hardcore trail riding.

A highlight for everyday use: The front headlight, which can be easily clipped under the stem via Monkey Link. Through contacts in the mount, it is powered directly by the large battery in the main frame.

Also practical is the chain guide and especially the generously sized chainstay protector, which ensures that the bike remains really quiet, even in rough terrain.

Shifting is done with the new electronic XT-DI2 drivetrain from Shimano. It can communicate directly with the motor, offering two new features: Free-Shift and Auto-Shift.

The Free-Shift mode allows you to shift without pedaling. When you shift while the crank arms are horizontal, the motor kicks in, driving the chain so that it can move to the next cog on the cassette.

The Auto-Shift mode, as the name suggests, is an automatic mode for shifting. The electronic drivetrain communicates with the motor and detects the riding situation thanks to the sensors in the motor. This means the motor measures the current torque, and an inclinometer indicates whether you are going uphill or downhill. Accordingly, the motor can shift into a lighter or heavier gear.

The Free-Shift function was really useful on the trail. Being able to shift without pedaling helps in many riding situations to have the right gear for what’s coming up. However, the Auto-Shift function didn’t quite convince us. The feeling of giving a large part of the control to the computer somehow doesn’t fit with the athletic approach we always maintain in our tests. Moreover, the system’s decisions only somewhat matched our needs.

In terms of shifting comfort, Shimano’s electronic ensemble clearly falls behind the competition from SRAM. Shimano’s shifting mechanism responds to every gear change with a fairly loud clank. SRAM’s brand-new Eagle Transmission is much quieter in comparison. And even under load, SRAM’s transmission simply shifts better.

The Shimano EP801 is a classic among EMTB motors. The progressive power delivery and the fact that its performance is directly proportional to the cadence give the motor a sporty character.

When you crank up the cadence, the motor’s power also ramps up. This means that you can control the motor very well with your legs. From about 80 RPM, and significantly earlier than with the Bosch SX motor, the maximum power output is achieved.

Unfortunately, the EP801 motor is clearly audible both under load and when descending. The high-frequency whirring uphill is noticeable even on deep gravel roads. The rattling of the gearbox during descent is audible on many EMTBs, and it’s also not to be missed on the Bulls Sonic Evo AM SL 3.

For many bikers, the motor is the number one buying criterion. And currently, there is a lot of movement in the market. Especially the new player DJI is seriously challenging the previous dominance of Shimano and Bosch with a new motor in the full-power segment. This table provides a quick overview of the most common alternatives to the Shimano motor and a direct link to the latest bikes with the respective options.

The installed Shimano motor packs a punch and, compared to many lightweight motors, it delivers the necessary power even at higher speeds to climb steep ramps effectively. In exactly these riding scenarios, the Sonic Evo truly shines. It is a true climbing artist.

Thanks to the steep seat angle, you sit far forward on the bike, putting a lot of pressure on the front wheel, while still ensuring the rear wheel has a lot of traction. This is also due to the very sensitive rear suspension, which allows the rear wheel to follow the ground well and always maintain traction. The motor’s power is transferred superbly to the ground, enabling the Sonic Evo to climb steep ramps confidently even on loose terrain.

Furthermore, the bike can be steered very precisely, because the head angle isn’t too slack. The bike responds very nimbly to steering inputs, giving you a real uphill flow. Last but not least, the uphill riding fun is also due to the bike’s overall low weight. This makes the bike very lively to handle in general.

We were surprised by how much fun you can have with so little travel. The rear suspension really impressed us. On one hand, the rear suspension is very sensitive, reacting smoothly to small bumps, but it also has a lot of pop, bringing a lot of liveliness to the bike.

The rear suspension builds up a lot of progression towards the end, preventing bottom-outs even on hard impacts or landings. If you hold the handlebars firmly, you can handle the Bulls quite well even beyond its intended use.

All in all, the Bulls is a confident descender that will be a blast for riders with an aggressive riding style. But it’s not a cushy ride that will carry you downhill effortlessly. The bike forgives few mistakes. It’s more of a sports car than a comfortable SUV. If the bike has a weakness, it’s the tires. At least depending on the intended use.

The tires are light and roll well, which is certainly advantageous on long rides, but they offer limited grip and don’t provide the ultimate puncture protection on descents. Riders who spend a lot of time in challenging terrain should consider mounting different tires.

We tested the Bulls Sonic Evo AM SL 3. If you want the full experience in the form of the AM SL-I, you’ll need to have €10,000 in your pocket. If you can do with a bit less luxury, you might want to check out the Sonic Evo AM SL 1 for €5199.

All information, including geometry charts and technical data for all models, can be found as always on the respective detail pages: