Bosch eBike Motor Laufleistung and Drive Sizing: A Checklist Before You Order a VFD, Servo Gearbox or Micro Stepper

Why this checklist exists

I'm the person who reviews orders for drive components before they go to purchasing. That job has been mine for 11 years, and since 2017 one of the product lines I review is Bosch eBike systems motors sold to dealers, builders and fleet operators.

I'm not writing this as an expert with a clean record. I've made and documented fourteen serious specification mistakes. Roughly $27,000 in wasted budget, plus the kind of phone calls that make you stare at your desk for a while before calling the customer back.

So this is not theory. The checklist below is the one I keep by my desk. It has five checks. It applies to a VFD order for a 5 hp motor, a servo motor with a gearbox, a micro stepper motor and a Bosch eBike motor replacement.

Check 1: What size VFD for a 5 HP motor? Don't start with horsepower

People ask this like there is one answer. If the motor is a normal 5 hp induction motor and the load is a centrifugal pump, a 5 hp VFD is often correct. But that is the start, not the decision.

The VFD has to supply the motor's nameplate full-load amps, not the mechanical horsepower. A typical 460 V three-phase 5 hp motor may show between 7 and 8 A on the nameplate. At 230 V, the same 5 hp motor may draw about 15 A. If the VFD datasheet lists continuous output current, compare that current to motor FLA. For constant torque loads, use the heavy-duty rating. For long cables or a hot panel, apply the derating the manufacturer gives you.

The mistake I made was matching '5 hp' in the catalog and ignoring FLA. The motor nameplate showed 8.5 A. The drive current rating was below that. On paper, it looked like a perfect match. In reality, it tripped when the motor reached rated load. I paid restocking and learned to look at amperes.

• Write down motor nameplate voltage, FLA, phase and rpm.
• Check both the VFD normal duty and heavy-duty output current ratings.
• Confirm the overload requirement: most loads need 150% for 60 seconds.
• Derate for ambient temperature and cable length if needed.

If the load is uncomplicated, the answer may still be 5 hp. But you need enough data to say that honestly.

Check 2: A servo motor gearbox needs a duty cycle and a radial load number

I regularly get requests like 'Need a 4:1 planetary servo motor gearbox for a 750 W servo.' That request alone is not enough.

A servo motor can deliver high torque during acceleration. A gearbox has to handle that torque, but it also has to handle the way the load applies force to the output shaft. The often ignored number is radial load, especially when the gearbox output uses a chain sprocket, belt pulley or pinion.

One of my documented mistakes was a servo motor gearbox sized by torque alone. The calculated torque was fine. The chain tension produced a radial load on the output shaft that was higher than the gearbox bearing rating. The bearing failed, the seal leaked, and the machine stopped. The gearbox datasheet listed the radial load limit. I simply did not check it.

• Provide a torque-time profile with acceleration, running and deceleration segments.
• State cycle time and how many reversals happen per minute.
• Check ratio, backlash and maximum input speed.
• Calculate radial and axial loads on the gearbox output shaft, not just output torque.

If you hear someone say 'it's only a small gearbox,' that is the moment to ask for the mechanical layout.

Check 3: A micro stepper motor's holding torque is not the torque you can use

Most micro stepper motor enquiries include frame size, current and holding torque. Those are real numbers, but they do not tell you whether the motor can move the load at the required speed.

Holding torque exists when the motor is at standstill or moving very slowly. As step rate increases, the available torque drops. The shape of that torque-speed curve depends on winding inductance, driver current, supply voltage and the selected step mode. A different motor with the same holding torque can stall at the same speed if it has a different winding.

I learned that with a replacement NEMA 23 micro stepper motor. Same frame, same holding torque, same current. I did not request the torque-speed curve at the customer's 24 V supply. At the required feed speed, the replacement could not deliver the torque that the old motor could. The axis stalled. On paper, the motors looked identical.

• Define the moving mass, friction, acceleration and maximum speed.
• Ask for a torque-speed curve measured with the same driver voltage and current you plan to use.
• Check winding inductance and driver capability together.
• Confirm whether microstepping is being used for smoothness or for increased step resolution.

Microstepping can smooth motion and reduce resonance, but it does not automatically improve absolute positioning accuracy. It certainly does not replace a torque curve.

Check 4: A Bosch eBike motor Laufleistung is a load profile, not a fixed number

I also receive requests that ask about a Bosch eBike motor Laufleistung. Laufleistung means distance travelled. On the surface, it sounds like the right way to compare motors: 10,000 km on one motor versus 20,000 km on another.

The reality is that distance alone is a weak measure. Two identical bikes with identical Bosch eBike systems motors can experience very different load. One commuter might ride mostly flat roads at low assist levels. Another might carry cargo on steep hills in Turbo mode every day. Both do 10,000 km, but the second motor and its internal gearbox do much more work.

I will not publish a single Bosch eBike motor Laufleistung figure because I have not seen a universal one published by Bosch. Anybody who gives you one exact number is probably giving you comfort, not data. What matters is the load profile behind the distance.

• Ask about elevation gain per ride and rider plus cargo mass.
• Ask which assist mode is used most of the time.
• Ask about stop-and-go riding versus long steady sections.
• Consider temperature, storage conditions and maintenance history.
• For fleet decisions, track fault data and physical inspections, not only odometer readings.

If you are ordering motors for a fleet, do not set replacement intervals based on mileage alone. Use the operating conditions and service records to set limits.

Check 5: A Bosch eBike systems motor is not one interchangeable part

The last check is about the product family in the title. A Bosch eBike systems motor is not one single motor. Active Line, Performance Line, Performance Line CX, Cargo Line and Performance Line Speed are different drive units with different torque, mounting and electronics. Even within one family, generations changed over the years.

If an order says only 'Bosch eBike systems motor' and nothing else, I stop and ask for the details. This is not a step you can skip.

• Take a close photo of the label on the motor casing.
• Write down the full model number and type number.
• Check the system generation and connector style.
• Record the bike brand, model and year.
• Note the display and battery part numbers if the motor is part of a complete system.
• Share any fault codes or failure description if this is a replacement.

I made the mistake of ordering by motor family name. The replacement motor was physically part of the same family but from a different generation. The connectors did not match. The correct unit was available, but I had lost a week and the customer's patience. A photo of the original label would have prevented it.

What I still have to remind myself

Most of my failures were not caused by not understanding motors. They were caused by skipping one line in a datasheet or ordering by a convenient label such as horsepower, frame size or motor family.

This checklist will not give you the exact part number. It will not replace the manufacturer's sizing tool or a proper technical review. What it does is stop the most expensive mistakes before they happen.

The honest part is this: if you do not have the data for one of these checks, do not guess. Ask the customer, take the photo, request the torque curve, or look at the nameplate. That extra step feels slow at the time. It is much cheaper than the alternative.