Bosch Hub Line put to the test: Here’s what the new Bosch motor is like to ride

Bike review: the Bosch Hub Line

The Hub Line is a sensible and presumably competitively priced addition to the Bosch range. It performs reliably and offers high peak power, good range and low pedalling resistance; above all, it is the well-developed Bosch ecosystem that makes it attractive. However, given Bosch’s excellent mid-drive motors, we would have expected even more in terms of riding feel and noise levels. - Adrian Kaether, Test & Technology Editor

Why a hub motor?

Whilst in the world of mid-engined cars, manufacturers are coming up with ever more spectacular performance figures and ever more innovative technology - Keywords: Gobao and Avinox eCVT - Whilst others are engaged in an arms race par excellence, Bosch, of all companies, is taking the opposite approach.

Like no other company, Bosch eBike Systems has long been synonymous with the mid-drive motor. Now, for the first time, the Swabian firm is expanding its product range to include a motor in the rear wheel hub: the Hub Line. Why? Naturally, they’re not revealing exactly why. Our guess: hub motors are simply in demand for certain types of bikes. They’re less conspicuous, easier to integrate and probably also cheaper than, for example, Bosch’s sporty Light Motor Performance Line SX (reviewed here).

Up to 45 Nm at 2.3 kg: The facts

Typical of hub motors: the Bosch Hub Line delivers only a modest amount of torque but a fairly high peak power output. Its weight is in line with the market standard and roughly on a par with budget hub motors such as the widely available models from Bafang. High-end hub motors on sporty gravel bikes, such as the X.20 from Mahle, significantly outperform the Bosch in terms of weight and torque, but offer lower peak power in return. Here is an overview of the facts about the Hub Line:

• ​Max. torque: 45 Nm
• Max. power: 400 watts
• Batteries: usually 360 or 400 Wh (in principle, all modern Bosch batteries are compatible)
• Range Extender: Compatible with Power More 250
• Weight: approx. 2.3 kg
• Diameter: approx. 100 mm
• Housing: black aluminium
• Special feature: complete decoupling at speeds above 25 km/h
• Integration: fully integrated into the Bosch Smart System

The key strength: integration into the Bosch system

As part of Bosch’s motor system, the Hub Line hub motor is also fully integrated into the Bosch ecosystem. This means that, in principle, the motor is compatible with all Bosch batteries and displays within the smart system – from the minimalist System Controller Mini Remote solution right through to the large Kiox display.

The control panels allow the motor to be connected to the eBike Flow app for navigation, activity tracking and even GPS and anti-theft protection. However, the latter requires, firstly, the additional Connect module and, secondly, a paid Flow+ subscription costing 5 euros a month or 40 euros a year. The Powermore 250 range extender (469 euros) can also be combined with the Hub Line motor.

Riding experience: a tailwind instead of strong legs

When it comes to mid-drive motors, Bosch is still right up there at the top in one area despite competitive pressure from DJI and others: the riding experience. Can the same be said of the Hub Line motor? Unfortunately, only to a certain extent. The motor’s quick response when accelerating is generally good, and it also reacts well to changes in pedalling input. In practice, we didn’t notice any significant delay, as is often the case with many budget hub motors. With assistance switched off and at speeds above 25 km/h, Bosch promises that the motor will disengage completely, and that’s exactly how it feels in practice.

However, even Bosch’s Hub Line cannot shake off the generally somewhat indirect riding feel associated with many hub motors. At low assistance levels, this isn’t particularly noticeable, but anyone switching to Auto or Turbo mode feels more as though they’re being propelled by a strong tailwind or an invisible hand than actively contributing to the propulsion themselves. This is handled much better by good mid-drive motors, including Bosch’s SX and CX models. They involve the rider more actively.

Technically, this makes sense because the mid-mounted motor transmits power directly to the chain or belt, whereas the rear-mounted motor has no direct connection to the drivetrain. This is good for reducing wear on the chain and belt, but bad for the riding experience. Nevertheless, it’s striking just how noticeable this decoupling is on the Hub Line. The high power output, on the other hand, is a clear advantage and ensures that the Hub Line doesn’t run out of steam as quickly as many other hub motors. It handles steep urban routes well, even if its climbing ability doesn’t quite match that of a mid-drive motor with a derailleur.

Range: Better than expected

The Hub Line also scores highly in terms of range, which is another of Bosch’s traditional strengths. With our admittedly the very light and fast Roadlite:On test bike from Canyon Fitted with fast gravel tyres, the Hub Line barely uses half a battery charge over 50 kilometres of city riding. This suggests a range of at least 80, or more likely 100 kilometres, on medium assistance. This is an excellent figure for the small 360 battery, especially as, whilst the bike is light and fast, being a single-speed means it places particular demands on the motor when pulling away from traffic lights.

Unfortunately, it’s not inaudible: the background noise

Alongside their sleek appearance, the low drive noise is a major advantage of many hub motors. Unfortunately, the Bosch model does not belong to this attractive ‘whisper-quiet’ class. The powerful and apparently efficient Hub Line does not make a loud noise when in operation, but it is always audible, even at low assistance levels. At the 25 km/h limit, the constant engagement and disengagement of the motor is particularly audible and detracts from the minimalist riding experience that many urban bikes with hub motors otherwise aim to provide. It’s a shame: given how quiet Bosch’s top-of-the-range CX motor has become whilst riding, we’d have expected more from this model.

Bosch Hub Line at a glance:

Strengths:

• Integration into the Bosch ecosystem
• High peak power for a hub motor
• Disengagement at speeds above 25 km/h

Weaknesses:

• Not really any quieter than a mid-engine car
• The driving feel is somewhat indirect due to the design of the system