The Stromer ST2 is a high-quality ebike, with a well-thought design, and electrical and mechanical components very carefully chosen to offer the best quality. A few weeks ago we contacted the Swiss producers of this ebike, who have kindly sent us a test model (the Stromer ST2 Sport Black version to be precise): here is our in-depth review of this ebike.

The Stromer ST2 ebike is available in two different versions: the Sport version (itself available in two sizes) and the Comfort version, with a step-through frame. There are two available colours: black and white. The city pack adds mud guards and a rear carrier to the ebike. We have tried the Sport version, in the bigger size, with a city pack.

Stromer ebikes: a short history

We think it interesting to briefly present the story of Stromer ebikes, to understand how the Swiss producer came to produce such a high quality ebike.

In the picture below it is possible to see one of the earliest ebikes produced by the Swiss designers. It is interesting to see how the fundamental traits of Stromer ebikes were already present: the rear hub motor, and the battery (a 360Wh one in this case) integrated in the down tube of the frame.  The components were just standard though, and not high quality ones, starting from the mechanical disc brakes to the average fork.

The ST1, introduced in 2011, was a big step forward. With this model, the current general design was introduced, and some interesting technical solutions were added to the mix, as for instance the regeneration of electrical energy when the brakes are actuated. The quality of the mechanical components was also improved: Magura hydraulic disc brakes, carbon fork…

The Stromer ST2 is the last declination of Stromer ebikes, a producer which is now part of the big BMC group. Without revolutionizing the ST1 project, the ST2 improves on it and updates it. Let’s get to know it better.

Electrical components

This Stromer ST2 ebike is based on a rear hub motor activated by a torque sensor, getting energy from a battery integrated within the down tube of the frame. The ebike is controlled through a touch-enabled display integrated within the horizontal tube of the frame, and through an app for Android smartphones.

The rear hub motor is gearless, 48V, 500W, with a maximum torque of 42Nm. It is important therefore to note that in many European countries, where the power limit is 250W, this ST2 would have to be registered as a motor bike.

It is in any case a “pedelec”, in the sense that the motor is activated only when the pedals turn. Between the cogset and the chainstay there is a torque sensor, used by the Electronic Control Unit to regulate the power of the motor, so that it follows the amount of power with which the cyclist pushes on the pedals.

Three levels of assistance are available. They can be selected through a keypad positioned on the right hand side of the handlebars, in a way which is easy to reach and use. The buttons are easy to feel, and back-illuminated. A third button is used to activate the front and back lights.

(Almost) all the other functions of the ebike are managed through a touchscreen display integrated in the horizontal tube of the frame. When the ebike is moving, the display shows the speed, the state of charge of the battery, and the level of assistance chosen (you can also choose to show the trip distance and time).

When the ebike stands still, it is possible to have access to a menu with many other options: locking the ebike; turning it off; regulating the sensor (more on this later); activating the walk assistance mode; and other settings which we will mention in the course of this test.

The display is pressure-sensitive, and this makes it less reactive and precise than the touchscreens of the smartphones to which we are used; at the same time, the positive side is that it works even with gloves on.

This Stromer ST2 ebike has three lights: the classic front and rear lights, and a day light to improve its visibility in traffic – and its aesthetic appeal (day lights are also a requirement for speed-ebikes in some countries). The day light dims down when you activate the normal front light (which delivers 170 lumen), and can also be completely turned off. Within the U formed by the day light a USB socket is hidden, which can be very useful in case you want for instance to use your smartphone as a gps navigator – a mode in which smartphones’ batteries last a very short time.

Talking of batteries: all the electrical components of this Stromer ST2 work thanks to a high-capacity battery (814Wh, 48V * 17Ah, Samsung cells); 814Wh are really a lot, and manage to deliver a very high range. The battery is perfectly integrated within the down tube of the frame, balancing the weight of the rear hub motor. The battery can be locked inside. When the lock is open with a key, the battery just slides out from the side in a very efficient way.

The battery can be recharged both on the bike itself, and when it is removed. The connector adheres to the EnergyBus standard, and has magnets so that it is easy to always put it quickly in the right way. The only problem with this battery is that it is not very easy to carry: its length prevails on the other dimensions, something which – together with a weight approximating 5 kgs – makes it uncomfortable to carry it (or a spare one if you ever need it).

The cabling is very well studied; as you can see from the pictures cables enter the frame as soon as they can, also due to the fact that the battery is located there.

The design of the ebike is therefore very “clean”, with the only exception of the motor, impossible to hide due to its generous dimensions.

For more informations on how these electical components actually behave, refer to the “road test” section below.

Mechanical components

The mechanical components chosen to equip this Stromer ST2 ebike are of high quality, and often produced exclusively for Stromer.

Shimano has been chosen to provide the components for the transmission system. There are two  chainrings, 52T and 36T; the cogset is a 10-speed one (11T to 34T). The rear derailleur is a Deor XT, while the front derailleur is from the 105 groupset; the handlebar switches are SLX. Needless to say, changing gears is always a quick and precise affair.

Brakes are an important aspect of an ebike weighing 27kgs, and which can reach a speed of 45 km/h. For this reason Stromer has chosen to mount Magura MT2/4 hydraulic disk brakes, with 180mm rotors. As we will see more in-depth in the “road test” section, brakes behave very well.

The bike has a nice rigid feel to it, also thanks to the 15mm through-axles with which the tyres are fixed. Absorbing shocks is a task mainly devolved to the Schwalbe Big Apple tyres. Mud guards are perfectly fixed, and have generous dimensions.

The rear pack carrier is of a smaller size, and can only bear a maximum of 10kg.

The saddle has been made specifically for this ebike model.

Stromer ST2 Road test

It is finally time to get on the saddle of this Stromer ST2 and see how it behaves on the road.

When starting to take confidence with the ebike, you are at first almost surprised by its power and acceleration, and by the brake power, but a few minutes are enough to understand and “tame” the ebike.

What most characterizes this ebike is the perfect balance and union between the high-power motor, and the great natural feeling of pedalling on it, thanks to a torque sensor which is extremely precise and reactive. What we mean to say is that even though it’s a high-power motor, you don’t perceive it as being something “other” than your own legs. With the third level the motor delivers all its power and it is easy to reach the speed of 38 km/h without barely noticing it; push just a bit on the pedals and soon you’ll be travelling at 45 km/h, the higher limit at which the electric assistance is deactivated. As soon as you push on the pedals the ebike accelerates in an impressive way, but never feeling twitchy or nervous – you always feel like you are in full control. The acceleration is great both when coming from a complete halt – for instance after a red light – and when you are already travelling at a decent speed: if for instance you are travelling at 20 km/h and you want to accelerate to overtake another bike, a couple of pedalling strokes will be enough to reach the speed of 30 km/h.

With the first level the ebike behaves in a very similar way to the European-style ebikes limited to a 250W motor: a speed of 25 km/h is easily managed even for long distances. The second level is of course an intermediate one, with the user being able to completely personalize it (as we will see in the paragraph dedicated to the app).

The wide range of gears available (from 52-11 to 36-34) allows the cyclist to easily find its preferred speed and cadence; by selecting the right gear and the third level of assistance, even the steepest climbs are not a problem.

The 814Wh of the battery allow for a very high range. Even using the third level, you won’t be able to completely discharge the battery if you use the ebike for a normal commuting trip in the city, even though once you go faster than 35-38 km/h wind resistance (and therefore the power consumption) increase a lot. Using the first level, this Stromer ST2 ebike becomes a great bike for a cycle tourist, allowing for a huge range.

From the display integrated into the horizontal tube of the frame it is possible, when the bike stands still, to regulate a few parameters, as for instance a greater or lesser sensibility of the torque sensor. The most interesting thing however is the regulation of the electricty regeneration system, which is activated when you brake. Basically, when you brake for more than about half a second (therefore when you are actually braking, not when you are just pinching the brakes for a quick control) the motor turns into a generator which helps slowing down the ebike (which in turn helps to keep the brakes cool and efficient) and at the same time generates electricity which is used to recharge the battery. It is the same principle of the KERS system used in Formula 1. As we were saying, using the display it is possible to set the intensity of this system, from zero to a maximum level. The standard setting (about half) turned out to be the ideal one for us; it is important to note that when you go for the maximum regenerating power it is frequent to block the rear wheel during an emergency brake (we have expressly tested this).

Speaking of braking: apart from the specific situation just described, the brakes are powerful and gradual, and always give a good feeling of being safe and in control.

More in general, the ebike offers a feeling of great stability, even at the high speeds which can be reached by pushing on the pedals – or going downhill. Where it lacks is in agility: the 27kg weight can be felt in quick and/or tight corners, where you have to slow down or emphasize the movement of your body in order to really push the bike around the corner (we are of course talking about a “sporty” kind of ride in tight and quick corners; for a more normal, urban use you won’t have many problems). The ebike reminds you of its weight also when you have to take it up some stairs; the weight however is well-balanced, and that helps a lot. Simple dirt roads are not a problem, but this Stromer ST2 is more of an urban jungle animal, preferring to avoid potholes and uneven surfaces.

We note  also that, because of how the gearless motor is built, it slows down the ebike a lot when it is turned off; pedalling when the motor is not on is therefore basically impossible.

The app used to manage the Stromer ST2 ebike

Even though the basic functions are all integrated in the on-ebike display, other functions need an app (for Android and iOs) to work. The link between the ebike and the app is done not through Bluetooth, but through a sim-card embedded within the frame. In this way, you can communicate with the ebike even from a distance.

The base screen shows the state of charge of the battery, the average speed, and whether the ebike is locked or not.

Thanks to a GPS sensor embedded within the ebike, another screen shows its position on a map.

Here you can activate the lock, and make the lights of the ebike blink for a few seconds.

Moreover, it is possible to finely adjust the settings relative to the second level of assistance. The first line, “range”, cannot be changed, but varies accordinf to how you set the other parameters: speed, torque, agility.

Accessories

The customer receives this box together with his ebike. Here there are the accessories that you can see in the picture, and the battery charger (a rather noisy one, it must be said).

Conclusion

If you live in countries in which the use of speed-ebikes is allowed, this Stromer ST2 can give a lot of satisfaction. We think it is perfect for the urban or extra-urban commuter, especially for those who have a garage available where to leave the ebike.

It could be great for cycle tourists as well: for daily trips you can use the third level to quickly leave the city, and then switch to the first level to enjoy many miles of riding. For longer trips lasting more days, the high range ensured by the 814Wh battery allow for a more relaxed search for charging points.

There are many other high-tech ebikes. In this case, we think that the high-tech part is very well-thought, and effectively useful for the cyclist. It’s not some gimmicky functions that are used once just to try it and then never again. This ebike was made in order to be actually used by real people, as you can tell from the presence of mudguards or from the fact that you can buy it in the Comfort version, with a step-through frame. It seems obvious to say this, but many high-tech ebikes are more a design experiment rather than object to be used by real people.

All of this comes at a price. In order to bring home this Stromer ST2, you will have to part with 5,500 of your hard-earned euros. The warranty is 2 years (or 1000 charging cycles) for the battery and the other components, and 3 years for the frame.