ABS

The ABS used by Stromer comes from the Italian manufacturer Blubrake. It was first offered on the ST5 model from 2021 onwards and was the first in the industry for S-pedelecs. It is based on electronic sensors, a transmitter disc on the front wheel, and an IMU acceleration sensor (Inertial Measurement Unit). Dieser Sensor misst die Fahrdynamik des gesamten Fahrrads – also die tatsächliche Geschwindigkeit, die Neigung, die Beschleunigung und die Verzögerung. Er dient als Referenz und erkennt, wenn das Hinterrad bei einer starken Bremsung abhebt und ein OTB (over the bar = Abgang über den Lenker) droht.

The actual braking force control is hydraulic. Without power (e.g. empty battery), the wheel continues to brake normally, but without ABS support.

At speeds under 5 km/h, the ABS does not engage. Additionally, the ABS system only affects the front wheel. If you brake too hard on the rear wheel, it can still lock up.

Where is the ABS installed?

The ABS is housed in the top tube. Retrofitting on non-ABS models is not possible due to the increased space requirements.

The operating modes

The Blubrake Gen. 2, available since 2021, has four predefined profiles: Safety, Standard, Performance, Extreme, and Off. When the ABS engages, there is no feedback through a pulsating brake lever, as is known from brake pedals in cars. Brake force increases in the order of the listed profiles, while ABS intervention decreases. 

1. safety mode: In safety mode, the braking force is reduced. This increases the braking distance enormously, so that there is a risk of being carried out of the bend even with an unlocked front wheel because the system does not provide enough braking force.

2. standard mode: Standard mode is well suited to e-bike beginners who often ride on gravel or poorly surfaced roads. The ABS reduces the braking force to such an extent that the front wheel does not lock up on dry and wet roads (on level ground). However, a practiced index finger of a fully concentrated rider still delivers the better performance.

3. performance mode: On loose surfaces, the system only intervenes when you have already released pressure from the brake lever. If you pull the brake lever all the way, you can briefly provoke a lock-up; then the system opens and gives you back control of the front wheel with a lot of braking power and short braking distances.

4. Extreme Mode: According to Blubrake, the mode is suitable for riders who want to slide the rear wheel, for example, through tight hairpin turns. The latter two profiles are not suitable for trekking rides or commuting.

See ‚Further information‘ below for more practical details.

Which mode does Stromer use?

Upon a corresponding request from the stromerforum.ch member Olfener, Stromer replied with the following:

Thank you for your inquiry and patience. The ST3 Pinion is equipped with the Blubrake ABS Gen. 2. Stromer uses the so-called standard configuration or standard mode of the ABS. The mode cannot be changed. In our opinion, the mode offers the best balance between performance and safety. However, the performance profile might also be set on the ST5.

Can the ABS be deactivated?

That's only possible with a trick – and the question remains why one would do that!

Man kann die untere Schraube des vorderen Bremssattels etwas losdrehen und den Sensor für die Raddrehzahl bewegen. Auf der ABS-Sensor-Halterung am Bremssattel steht «1 mm Distance» (zur ABS-Geberscheibe an der Bremsscheibe). Wenn man den Sensor nach aussen schiebt und die Schraube wieder anzieht, kann das ABS die Radbewegung nicht mehr messen. Im Display leuchtet das ABS-Symbol dauerhaft gelb und das ABS ist ausser Funktion (Source).

A disadvantage of this method is also that the service symbol, a warning message, or a firmware upgrade may no longer be displayed because the ABS signal lights up permanently.

Problems

See BREMSEN - 'Bleeding the brakes / problems with the ABS'
See FAQ - ‚ABS – Symbol – Functions‘

More info

The Blubrake ABS G2 anti-lock braking system in the test
Practical test: ABS for bikes | Bosch anti-lock braking system really good?