Lightweight e-bikes – just a trend?
Introduction
In the world of two-wheeled mobility, we have been observing a remarkable trend towards light and ultra-light e-bike models since the 2020s. This development was ultimately driven by users, who increasingly expressed their desire for light urban or sporty e-bikes directly or indirectly to manufacturers. Product managers of some component manufacturers and some niche providers of light e-bikes recognized this trend a few years ago and began to react accordingly. We at Möve were also among these manufacturers and in 2019 we presented our first very light single-speed e-bike, the Urban:Airy , which weighed just 16 kg.
We also presented the lightweight Trekking E-Bike Airy , which is equipped with a Pinion gearshift and RockShox air suspension fork and weighs 19 kg.
Long-standing focus on reach and performance
The focus of the first generation of e-bikes was on range and performance. Faster, higher, further was the motto that most e-bike manufacturers were committed to in the first decade of e-bike development. This trend was driven by the dominance of mid-engine system manufacturers such as Bosch. The design-related product properties of these mid-engines made it possible to satisfy the target group's "hunger for performance" with manageable development effort. In general, it is important to know that with mid-engines it is easier to increase performance than to reduce weight or size, because this design inevitably requires the use of a relatively heavy gearbox.
In addition, in this early period of e-bikes, the industry focused on the target group of best-agers, i.e. a target group that was to be brought back to the bike by means of electric pedal support, which was very successful. These best-agers were followed by a much younger and more performance-oriented target group, namely the first e-mountain bikers. They wanted to climb the mountains, also powered by the mid-engine, and transfer the additional power gained into new speed records. However, the driving characteristics of these first e-mountain bikes were more similar to those of motorcycles than to those of traditional mountain bikes.
In the first years of this groundbreaking e-bike success, i.e. between 2012 and 2018, more and more component manufacturers, in addition to Bosch, recognized the opportunity for double-digit growth in an emerging market and began to secure market share and emulate the market leader Bosch. The result was the annual market launch of ever new mid-engine drive systems such as those from Brose, Yamaha or Shimano. But they all had one thing in common: more torque on the bottom bracket axle, with the products differing in nuances such as the gear function or the housing materials. At that time, hub motor providers were leading a shadowy existence in Germany, largely due to the technical and subsequent economic bankruptcy of the Bionix hub motor.
Vivax and Fazua as pioneers for lightweight e-bikes
Back in 2017, I personally noticed the drive system from the Austrian manufacturer Vivax, the Vivax Assist Motor, which was already ready for series production at the time. This drive, specially developed for racing bikes for retrofitting in the seat tube, was powered by a battery cleverly hidden in the bottom of a drinking bottle and coupled to the bottom bracket axle via a spiral-toothed cone pair. This e-bike drive was the first to take a different approach, namely one that was independent of torque, because the additional drive energy was introduced in a cadence-controlled manner. This led to a riding experience when pedaling that was very similar to cycling and was particularly interesting for ambitious racing cyclists. With the Vivax Assist Motor, they could now also enjoy electrically assisted pedaling without having to officially out themselves as e-cyclists. I even believe that the Vivax Assist motor was the reason for the first e-doping cases in cycling, but at the same time it confirmed the potential of this technology, especially for the development of very light e-bikes such as the racing bike model group.
The start-up Fazua, which first attracted attention in 2014 as part of a successful Series A financing round from the Hightech Gründerfonds, took a different but also technically very sophisticated approach. We met the founders at the HTGF pitch events when we presented our cyfly technology.
The Munich-based start-up with the mid-engine drive of the same name pursued the innovative approach of decoupling the electric motor from the bottom bracket gear. The gear was permanently installed in the bike and activated for electrically pedal-assisted driving via a removable in-tube battery electric motor unit. This led to the unique possibility that the e-bike could be used as an almost normal bicycle after removing the heavy electric motor battery unit, making it the first series-ready hybrid of an e-bike-capable biobike. Fazua later made its breakthrough in the mass market for lightweight e-mountain bikes and was fully taken over by Porsche in August 2022.
Mahle makes a breakthrough with a sophisticated drive system for lightweight e-bikes
Mahle, a well-known automotive supplier like Bosch, recognized the trend toward lightweight e-bikes and, through its Spanish spin-off Mahle Smartbike Systems SLU, introduced the ebikemotion X35 in 2018, the first mass-market e-bike system for e-gravel and e-racing bikes. Mahle combined what it claims to have developed itself as a very lightweight rear-wheel gear motor with a weight-optimized 250 Wh battery for the down tube. The system weight of the entire drive unit was thus less than 4 kg for the first time and could be produced in large quantities on a scalable basis, which subsequently led to the appearance of numerous lightweight and ultra-light e-bikes. What Mahle had not actually planned at the time, but later turned out to be one of the main reasons for the very rapid breakthrough of this system, was the fact that many manufacturers repurposed the use of the E-system for chic and lightweight design e-bikes for the city in order to emulate the meteoric success of the VanMoof brand, which had appeared at the time with technically not quite as innovative but more sophisticated MeToos. Thus the Urban E-Bike was born and to this day ensures the rapid spread of lightweight e-bikes that are reminiscent of the original classic bicycle that is valued by enthusiasts.
The battery as a weight driver
But how did Mahle manage to reduce the system weight to under 4 kg? Of course, Mahle essentially only "cooks" with "water". Nevertheless, brave and clever product managers at Mahle decided on three major compromises or solutions. Firstly, the battery, which was a major weight driver, was "castrated" in size and an additional range extender battery (power bank) in the form of a drinking bottle was offered for longer tours, which could simply be connected to the charging socket of the main battery. Secondly, the battery was designed as a permanently installed element in the down tube, which makes a heavy and bulky battery carrier with an integrated battery lock, which is required for semi-integrated batteries, superfluous. The engineers at Mahle made use of the following knowledge:
Light e-bikes can be accelerated relatively easily on flat roads and without strong headwinds, especially if the target group is sportier and younger, i.e. relatively little battery energy is needed for acceleration.
With light e-bikes, it is relatively easy to ride well over 25 km/h on flat roads and without headwind, i.e. in these situations no energy is needed from the battery, as the electric support must be switched off above 25 km/h in Germany.
Light e-bikes for sportier users do not require as much torque, which means the motor can generally be smaller and lighter.
The average distance covered with the e-bike is only 10.3 km, which means that on average and in daily use, a battery with a lot of energy is not needed, especially since the optional power bank is available for longer tours.
A lightweight e-bike can also be carried completely when stored in the basement or apartment, i.e. the battery does not necessarily have to be removable, which allows the use of a lighter, permanently installed battery.
With the ebikemotion X35 and the later X35+, Mahle has therefore opted for a less powerful gear motor in the rear wheel hub and a smaller battery built into the frame. As a result, lightweight e-bikes are not currently based on rapid optimization of the energy density of the batteries, as most people think, but are "due" to the willingness of users to compromise and the courage of the developers.
Of course, the overall weight of e-bikes will benefit from the increasing energy density of the batteries in the future. Modern lithium-ion batteries currently achieve an energy density of up to 140 watt hours per kg. Experts assume that the energy density will increase to 300 to 350 watt hours per kg of mass by 2030.
Until then, manufacturers of lightweight e-bikes will have to continue to make compromises and look for other solutions to make the bikes even lighter. Promising approaches include further optimizing the weight of the e-motors and reducing the weight of relevant e-bike components such as the frame through measures such as lightweight material construction.
Conclusion
The trend towards lighter e-bikes is more than just a fad - it is a symbol of innovation and future-oriented mobility. These new generation lightweight e-bikes offer improved handling, agility and an authentic riding experience that is very close to that of a traditional bicycle. They are ideal for people who live in the city and are looking for an easy-to-maneuver, environmentally friendly means of transport. Active users also benefit from the combination of exercise and support from the motor.
From elegant city bikes to robust touring bikes - the range of lightweight and ultra-light e-bikes shows that there is now a model to suit every preference and every need. The future of e-bike innovations looks promising. Advances in battery technology, optimized motor designs and the use of innovative materials will continue to play a central role. A major breakthrough is expected in the next ten years when the energy density of the battery cells doubles and the battery housing is integrated into the frame as a supporting structure.
Lightweight e-bikes represent a perfect combination of technological innovation, sustainable design and practical everyday usability and will be the rule in the future rather than the exception. Lightweight e-bikes already represent an exciting time in the world of two-wheeled mobility, appealing to both enthusiasts and everyday bike users.