Bosch Performance Line CX Gen 2: the reference for e-MTBs from 2016-2019
The Bosch Performance Line CX Gen 2 is probably one of the most widely used electric bike motors of its generation. Produced from 2016 to 2019, it has equipped thousands of e-MTBs and trekking bikes across many brands:
- Haibike
- Cube
- Trek
- Scott
- Moustache Bikes
- Riese & Müller
With its 75 Nm of torque, it has long been considered the most dynamic motor on the market. Even today, many examples exceed 20,000 to 30,000 km without major failure.
The main issues encountered
1. Premature bearing wear
This is probably the most common mechanical problem on heavily used motors.
The symptoms are:
- dull rumbling;
- bearing noise;
- vibration in the pedals;
- pedalling resistance.
When the bearings start to wear, water and impurities can enter the motor and accelerate the wear of other internal components.
2. Infiltration of water and dust
The early generations of the CX Gen 2 were criticised for their imperfect sealing around the bottom bracket.
Observed consequences:
- grinding noise;
- internal corrosion;
- gear wear;
- bearing degradation.
Bosch has also marketed a repair kit including :
- new side casing ;
- bearings ;
- gears ;
- improved seals.
3. Internal freewheel problem
A relatively well-known failure concerns the freewheel mechanism ("freewheel").
The symptoms are:
- motor that runs but no longer transmits power correctly ;
- high resistance when pedalling ;
- feeling of engine braking ;
- loss of propulsion.
The problem mainly occurs on older motors that have been ridden in the rain or stored in humid conditions.
4. Complete system shutdowns
Several users have reported :
- assistance that disappears suddenly ;
- screen that stays on but motor inactive ;
- random restarts.
In many cases, the causes are external to the motor :
- battery ;
- connectors ;
- moisture in the wiring harness ;
- Bosch management software.
5. Rapid wear of the transmission
The CX Gen 2 used a small 14-tooth chainring with internal gearing.
This design provided a lot of torque but increased :
- chain wear ;
- cassette wear ;
- the risk of chain breakage.
This is one of the most common complaints about this generation.
Bosch will completely modify this architecture starting from Gen 4.
6. Internal noises
After several thousand kilometres, some owners report :
- clattering ;
- cracking ;
- metallic noise when pedalling ;
- gradual rumbling.
In the majority of cases, these noises are related to :
- the bearings ;
- the secondary gears ;
- the internal freewheel.
What has made its reputation
Despite these flaws, the CX Gen 2 is still considered one of the most robust motors of its time.
Its qualities :
- significant torque ;
- very sporty assistance ;
- excellent traction uphill ;
- availability of parts ;
- superior repairability compared to many competing motors.
Many specialised workshops still repair today :
- the bearings ;
- the gears ;
- the freewheels ;
- the motor casings.
Conclusion
The Bosch Performance Line CX Gen 2 is often considered the "diesel" of e-MTBs: heavy by today's standards, but extremely durable. Its main weaknesses concern :
- the bearings ;
- the sealing of the early versions ;
- the internal freewheel ;
- the accelerated wear of the transmission.
In contrast, it suffers much less from serious electronic failures than some competing motors of the same era. For a second-hand purchase, a CX Gen 2 with less than 15,000 km and showing no bearing noise or play in the bottom bracket remains a particularly safe choice today.