Lightest Mid Drive Motor Review: Top Ultra-Lightweight Options Compared (2025)
A mid-drive motor’s weight directly affects handling, acceleration, and how natural the bike feels under power. For riders building or upgrading a lightweight e-bike—especially for climbing or tight trails—every pound matters. The lightest production mid-drive motors today come in at roughly 4.2 to 5.5 lb, but the trade-offs between torque, battery weight, and integration are real. This review covers the lightest options, how to verify fit, what can go wrong if you choose wrong, and which motor best fits your riding style.
Quick answer
The TQ HPR 50 (4.2 lb / 1.9 kg) and Fazua Ride 60 (4.4 lb / 2.0 kg) are the lightest mid-drive motors you can buy in 2025. Below 5 lb, peak torque stays between 50 and 60 Nm—enough for most rolling terrain and moderate hills, but noticeably weaker on sustained grades above 10%. For riders who need more climbing power, the Shimano EP8 RS (5.3 lb) delivers 85 Nm while still staying under 6 lb. The best balance for most people lands at 5.0–5.5 lb with 60–75 Nm, offering enough torque for daily commutes and light trail riding without the weight penalty of a full-power motor.
Comparison framework
Three factors determine whether a lightweight mid-drive will work for you: torque, battery pairing, and frame compatibility. Lighter motors use smaller stators and lower gear reduction, reducing torque but also cutting weight. The table below compares the top ultra-light models (2025 specs, manufacturer-reported). Note that total system weight also depends on battery size—a 300 Wh battery adds about 3.5 lb, a 500 Wh battery about 5.5 lb.
| Motor | Weight (approx) | Peak Torque | Continuous Power | Battery Options | Best Use Case |
|---|---|---|---|---|---|
| TQ HPR 50 | 4.2 lb (1.9 kg) | 50 Nm | 250W | Internal or frame-integrated (300–430 Wh) | XC/marathon racing, sub-30 lb builds |
| Fazua Ride 60 | 4.4 lb (2.0 kg) | 60 Nm | 250W | Removable down-tube integrated (430 Wh) | Gravel, road, lightweight trail |
| Mahle X20 | 4.6 lb (2.1 kg) | 55 Nm | 250W | Hub or frame-integrated (250–350 Wh) | Commuting, fitness, recreational |
| Shimano EP8 (RS) | 5.3 lb (2.4 kg) | 85 Nm | 250W | External or semi-integrated (any standard battery) | Trail riding, light enduro, all-day climbing |
| Bosch Performance Line SX | 5.5 lb (2.5 kg) | 55 Nm | 250W | Fully integrated (400–545 Wh) | Light trekking, urban, fitness |
Top Pick: For riders who want the absolute lightest setup with responsive pedal feel, the TQ HPR 50 delivers an unmatched 4.2 lb weight and uses a harmonic‑pinion drive with near-zero drag when pedaling unassisted. Its torque sensor accuracy is among the best in class—you feel immediate response with no lag. It’s the go-to for weight-weenie mountain builds.
Specs are manufacturer-reported; actual weight varies slightly with cable routing and mounting hardware. Always verify with your bike or motor supplier.
How to verify motor weight and fit before buying
Before committing to an ultra-light motor, check the following on the intended frame or bike:
- Bottom bracket shell width and motor mount pattern. Most lightweight mid-drives (TQ, Fazua, Mahle) use proprietary interfaces. Measure your frame’s shell width (typically 68–83 mm) and compare with the motor’s required insert width. The brand’s website or a dealer can confirm compatibility.
- Manufacturer’s spec sheet for total system weight including hardware. The TQ HPR 50, for example, is often listed at 1.9 kg, but adding the mounting brackets, bolts, and cable connectors can add 0.1–0.2 lb. The same applies to the Fazua Ride 60—check the included items list.
- Battery integration compatibility. If you plan to use a third-party battery, verify the voltage (usually 36V) and BMS communication protocol. Many lightweight motors only work with their own battery and display, so buying a complete bike or a full kit is safer.
Best-fit picks by use case
Ultralight XC and marathon racing
TQ HPR 50 – At 4.2 lb, it’s the lightest mid-drive available. The harmonic‑pinion drive produces virtually no drag when pedaling without assist, which matters for long climbs where you switch between power and pure muscle. Torque is modest (50 Nm), but the motor’s fast torque sensor response means you never feel a lag even on steep pitches. Pair with a 300–350 Wh battery (2.8–3.5 lb) for a total system under 8 lb. Real-world range: 15–25 miles in high assist, 30–40 miles in eco mode. This motor shines on technical terrain where you need precise modulation—the sensor reacts to pedal pressure in milliseconds, letting you feather power through rock gardens without over-accelerating.
Gravel and adventure
Fazua Ride 60 – Weighing 4.4 lb, it offers 60 Nm of torque and a removable 430 Wh battery that integrates cleanly into down tubes. Ideal for gravel rides where you want assist on headwinds and rolling terrain but still want the bike to feel nearly normal when the battery runs out. The freewheel mode has very low drag (similar to a bottom bracket without a motor when coasting). However, note that the motor’s 60 Nm will struggle on sustained gravel climbs above 10% grade if you’re carrying bikepacking gear. In those cases, dropping to a lower gear and pedaling harder is necessary.
Light trail and all‑day climbing
Shimano EP8 (RS) – At 5.3 lb, it’s heavier than the pure‑light options but delivers 85 Nm of torque, enough to handle moderate climbs without needing a huge battery. The RS (Race Spec) version shaves about 0.3 lb off the standard EP8 by using a carbon composite cover and lighter gears. This is the best choice for riders who want trail capability at a still‑light weight. The torque sensor is slightly less refined than the TQ or Mahle—there’s a tiny delay on rapid pedal inputs—but the extra torque makes up for it on loose, steep climbs. Pair with a 500 Wh battery for 25–40 miles of trail riding.
Commuting and fitness
Mahle X20 – 4.6 lb with 55 Nm. The X20 is designed for bikes where assist is a subtle companion—think flat bars and moderate hills. It pairs with hub batteries (up to 350 Wh) or a frame‑integrated pack. The motor is nearly silent and provides very natural pedal feel, making it a strong option for riders who just want a little help without a heavy system. One limitation: the Mahle motor is not designed for extreme torque loads. If you frequently start from a stop on a steep hill (e.g., a 15% grade), the motor can overheat and throttle back power after 60–90 seconds of continuous climb. For flat commutes and gentle rolling terrain, it’s excellent.
Trade-offs to know
Torque vs. weight – Ultralight motors (under 5 lb) cap torque at 50–60 Nm. That’s enough for most hills if you’re fit, but on steep sustained grades (over 10%) you’ll feel the limitation. A real-world example: riding a 32-lb e-bike up a 12% grade with a 50 Nm motor requires steady pedaling effort at low cadence; the motor will help but won’t pull you up effortlessly. In contrast, a 75 Nm motor (e.g., Bosch Performance CX, 6.2 lb) can handle that same climb at a conversational pace. If you live in a mountainous area, consider whether 50 Nm is enough for your usual routes.
Battery weight vs. range – A lightweight motor is only half the equation. A 500 Wh battery adds about 5.5 lb. To keep total system weight under 10 lb, you’ll likely need a 300–400 Wh battery, which reduces range to about 20–40 miles depending on assist level. For long day rides (50+ miles), you may prefer a slightly heavier motor (5.5 lb) paired with a standard 500 Wh pack to avoid range anxiety. The weight penalty of the extra battery about equals the motor savings.
Integration and compatibility – Many ultralight motors (TQ, Fazua, Mahle) are designed for specific frame interfaces. Retrofitting an existing bike is often impossible—these motors are typically sold as part of a complete bike or a custom motor-battery kit. Attempting to mount a Fazua Ride 60 on a non-Fazua frame requires a special adaptor bracket that rarely lines up with standard bottom bracket holes. The result: poor chainline and motor cooling issues. Always check compatibility before buying a motor alone.
Cost – Ultralight mid-drives typically cost $1,500–$2,500 for the motor alone, and complete bikes using them start around $4,000. The trade-off is real: you pay a premium for grams saved. If you’re on a budget, a heavier motor like the Shimano EP8 (non-RS) at around $1,200 gives you 85 Nm for less money, but adds 1–1.5 lb.
Thermal performance on sustained climbs – Lightweight motors have less mass to dissipate heat. On a long climb (20+ minutes at high assist), a 50 Nm motor may reach thermal derating limits earlier than a heavier unit. The Mahle X20 and Fazua Ride 60 both show noticeable power reduction after 10–15 minutes of continuous full-throttle climbing. If your regular route includes long, sustained grades, consider the Shimano EP8 or a heavier motor with better heat management.
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Ryan Williams has spent over 8 years testing, repairing, and writing about electric bikes. He has personally ridden and reviewed 150+ e-bike models from brands like Lectric, Aventon, Rad Power, Super73, and dozens more.
Before founding EBIKE Delight, Ryan worked as a bicycle mechanic for 5 years at independent bike shops across California, where he specialized in e-bike conversions and electrical system diagnostics. He holds a Certificate in Electric Vehicle Technology from the Light Electric Vehicle Association (LEVA).
Ryan’s work has been cited by Electric Bike Report, Electrek, and BikeRumor. When he is not testing the latest e-bike on California backroads, he is in his workshop tearing down batteries and controllers to understand what makes them tick — and what makes them fail.
Areas of Expertise
E-bike performance testing and real-world range verificationBattery diagnostics, charging best practices, and safetyBrand comparisons: Lectric, Aventon, Rad Power, Super73, and moreError code troubleshooting across major e-bike systemsE-bike laws, registration, and compliance by state
Ryan believes every rider deserves honest, hands-on information — not marketing hype.