Home visit / E-bike: The development of compact and lightweight e-bike motors has significantly changed the market in recent years. A key player in this segment is the Bavarian company TQ, which has been instrumental in shaping the trend of light e-MTBs, particularly with its HPR50 drive, and is further advancing this trend with the HPR60 and HPR40. We visited their facilities in Inning am Ammersee, spoke with the developers about transmission concepts and sensor technology, and took a detailed look at their local production.
The story of TQ: From electronics service provider to e-bike pioneer
That TQ plays such a prominent role in the bicycle sector today was unforeseeable when the company was founded in 1994. Originally started as a two-man operation, the company initially focused on electronics services and early robotics. Today, TQ employs around 2.000 people worldwide, approximately 200 of whom work in the e-bike division at the Ammersee location.
The journey to bicycle drive systems only began around 2010 and is closely linked to Toni Rossberger. The former extreme athlete and machine fitter, who had long been developing solutions for TQ in areas such as aerospace, became personally involved in an e-bike startup. However, the prototypes at that time were heavy, bulky, and relied on inefficient chain designs. Rossberger sought a rotationally symmetrical, compact solution. Since existing industrial gearboxes for e-bikes were neither efficient nor affordable, he developed his own concept, which ultimately laid the foundation for today's TQ portfolio.
The technology: The harmonic pin-ring gear
The heart of the TQ drive system is the so-called pin-ring drive, also known as the "HPR" (Harmonic Pin-Ring Drive). Unlike classic coaxial drives or multi-stage gear designs, this construction enables extremely compact, ring-shaped power transmission. This results in very high torque density in a very small installation space. Another technical advantage lies in its integration around the bottom bracket, which allows for a low Q-factor (the distance between the pedals) and short chainstays on the bicycle frame.
TQ's first production motor, the HPR 120S, was launched in 2014. With a maximum torque of 120 Nm, the unit was far ahead of its time – for comparison, a second-generation Bosch Performance Line CX delivered 75 Nm at the time, albeit with a higher weight. Even though the 120S might seem like a dinosaur from today's perspective, it demonstrated the fundamental performance capabilities of pin-ring technology.
Innovation through software: force measurement instead of a classic sensor
One of the biggest design challenges with mid-mounted motors is integrating the torque sensor. This typically requires a hollow shaft and additional space, which contradicts the goal of an extremely compact motor. TQ therefore opted for an unconventional approach: The drives do without a conventional torque sensor.
Instead, TQ uses proven strain gauges attached to the bottom bracket axle bearings. These precisely measure the vertical forces and the minimal twisting that occurs when pedaling. The real magic happens in the software: A highly complex algorithm processes this data in real time and calculates not only the applied torque, but also analyzes pedaling technique, weight distribution (left/right), and even detects whether the rider is standing up. This interplay of simplified mechanics and advanced software is a key factor in the compact size of current TQ motors.
The paradigm shift: From powerhouse to light-assist
Despite their initial focus on maximum performance, TQ recognized early on that direct competition with industry giants like Bosch, Shimano, or Brose in the high-power segment would be counterproductive. Test rides and data analysis with riders who were critical of conventional e-bikes revealed a new requirement: a motor should preserve the natural riding feel of an unmotorized bike, rather than masking it with sheer power.
From this "submarine project" emerged a significantly lower gear ratio drive with less power, reduced flywheel mass, and minimal noise. This marked the birth of the HPR50. The motor was designed for riders seeking sensitive, rewarding assistance without sacrificing the handling of an agile trail bike. Its integration into models from major manufacturers like Trek finally brought TQ its definitive breakthrough in the rapidly growing light e-MTB segment.
The evolution of the HPR series: HPR60 and HPR40
TQ's product strategy is also interesting. The HPR60, which succeeded the HPR50, offers 10 Nm more torque and 50 watts more peak power in the same housing, coupled with optimized thermal management. This backward compatibility is a major advantage for frame manufacturers and end users, as the form factor remains the same.
The minimal-assist concept is currently taken to its extreme with the HPR40. This motor weighs just over one kilogram and is specifically designed for e-gravel and e-road bikes. Visually, the motor disappears completely behind the chainring, making such bikes virtually indistinguishable from their conventional counterparts.
A look at production at Ammersee
A true highlight of the visit was the tour of the production facilities in Inning. What is often used as a mere marketing label in today's bicycle market ("Engineered in Germany") is tangible reality here. TQ's vertical integration is impressive. A large proportion of the transmission components, the complex power electronics, and the final assembly of the motors take place within the company's own network (Inning, Peiting, Delling).
On the assembly lines, the components are joined together in a semi-automated process where precise robotics and skilled manual labor work together seamlessly. The close proximity between the research and development department and series production is particularly noteworthy. This allows modified components or prototypes to often be tested and implemented within 24 hours – a tremendous advantage in such a fast-paced technological environment.
Innovation pays off
The visit to TQ E-Bike demonstrated that innovation doesn't always mean striving for the highest performance figures. By boldly differentiating themselves technologically with pin-ring technology and software-based power measurement, TQ has carved out a niche that has since become one of the most important trends in the bicycle industry. The high degree of local manufacturing and the continuous, evolutionary development of the motors in the same form factor make the system extremely attractive not only to bicycle manufacturers but also to tech-savvy and athletic cyclists.