How to Install a Mid-Drive Motor on Your Bike (DIY Guide)
In this hub: Conversion Kits & DIY Hub — browse the recommended reading order.
A mid‑drive conversion is the closest thing to “my legs got superpowers.” It’s also the conversion style where careful fitment and torque matter most. This guide walks you through a safe, repeatable install with the checks that prevent annoying noises and drivetrain wear.
Quick overview
Best for: hills, cargo, longer rides, and riders who want a natural feel.
Time: 3–6 hours for first-timers.
Tools you must have: crank puller + bottom bracket tool.
Before you start: compatibility checklist
- [ ] Bottom bracket shell width: 68mm or 73mm (common)
- [ ] Bottom bracket type: threaded (ideal) or compatible press-fit solution
- [ ] Frame clearance: chainring and motor housing won’t hit chainstays
- [ ] Brakes are strong (or you’ll upgrade)
- [ ] Battery mounting plan (triangle is best)
If you’re unsure which kit fits your bike, start here: How to Choose the Right E‑Bike Conversion Kit for Your Bike
Tools and supplies (the “don’t regret it later” list)
Required
- Crank puller / extractor (matches your crank type)
- Bottom bracket tool (matches your BB)
- Hex keys
- Torque wrench (highly recommended)
Nice to have
- Medium threadlocker (for specific fasteners if manufacturer recommends)
- Grease (anti-seize on threads)
- Cable wrap + zip ties
- Bike stand (makes everything easier)
If you have a press-fit bottom bracket
Press-fit frames aren’t automatically “no,” but they can add complexity:
- You may need an adapter to convert press-fit to a threaded interface
- Fitment can vary by frame brand and BB standard
If you’re not comfortable diagnosing press-fit standards, a bike shop can identify the exact BB type quickly and tell you whether an adapter is reliable for your frame.
(For most first-timers, a threaded BB donor bike is the easiest path.)
Step 1: Remove cranks and bottom bracket
1) Shift to the smallest chainring/cog (reduces chain tension).
2) Remove pedals (if needed for access).
3) Remove crank bolts, then use the crank puller to remove cranks.
4) Remove the bottom bracket.
Note: Some BBs have reverse threading on the drive side—check your BB type so you don’t fight it the wrong direction.
Clean the BB shell threads and face.
Step 2: Dry-fit the motor (verify clearance)
Before you fully tighten anything:
- Slide the motor into the BB shell
- Check housing clearance to the chainstays
- Check that the motor sits square and the mounting plate can clamp properly
If it barely clears, you may need spacers or a different chainring offset to protect chainline.
Step 3: Mount the motor and secure the lock rings
1) Install the motor through the BB shell.
2) Install the mounting plate/bracket per kit instructions.
3) Install lock rings and tighten to spec.
Why torque matters: A loose mid‑drive can creak, shift under load, and chew up hardware. Tightening to the manufacturer’s spec is the difference between “solid” and “noisy.”
Step 4: Install the chainring and check chainline
Chainline is the “hidden key” to a smooth mid‑drive.
Quick chainline test
- In the middle cassette gears, your chain should run fairly straight.
- If it angles aggressively, you’ll get noise + wear.
Fixes (in order): 1) Use the chainring offset that came with the kit
2) Add/remove spacers as the manufacturer allows
3) Adjust rear derailleur indexing after the drivetrain settles
Step 5: Battery mounting (do this like it’s permanent)
Best: triangle mount
- Better handling
- Less stress on racks
- Usually more secure
Rack mount
Works, but re-check bolts after early rides and don’t overload the rack.
Safety reminder: Follow CPSC charging guidance: be present while charging, use the correct charger, and avoid modified packs. CPSC charging safety
Step 6: Wiring and cable routing (clean = reliable)
- Route cables away from the chain, crank, and tire.
- Use gentle bends; avoid pinching.
- Add drip loops near connectors if you ride in rain.
Common connections:
- Battery to controller
- Display
- Speed sensor
- Brake cutoffs (optional but recommended on higher power)
- Gear sensor (optional but helpful for smoother shifting)
Step 7: Setup and first test (do this in a safe area)
1) Power on and confirm the display works.
2) Set wheel size in the display/controller if applicable.
3) Test assist at the lowest level first.
4) Test brake cutoffs (if installed).
5) Test shifting under light load.
Shift technique (mid‑drives)
Easing off power during shifts dramatically reduces drivetrain wear. Think: “soft pedal for half a second” as you shift.
Torque “cheat sheet” (generic guidance)
Every kit is different—always follow your kit’s manual first. But as a sanity check:
- Big clamp/lock ring hardware should be tight enough to prevent movement under hard pedaling
- Use a torque wrench where the manufacturer provides a number
- Re-check after the first 10–20 miles
If you don’t have a torque wrench, borrow one. Stripping threads is not a fun DIY lesson.
Speed sensor placement (small part, big problems)
Most mid‑drives need a speed sensor + magnet.
- Put the magnet where it won’t get knocked off (spokes are common)
- Align the sensor and magnet gap per kit instructions
- Secure the sensor cable so it can’t snag brush or debris
If your display shows “0 mph” while moving, this is the first thing to check.
Weatherproofing basics
Even “water resistant” kits hate pressure washers and deep puddles.
- Don’t blast the motor or connectors with high-pressure water
- Apply dielectric grease only if the manufacturer recommends it
- Keep connectors oriented so water drains away (drip loops)
A smart first ride plan (20 minutes)
1) Ride in a quiet area at low assist.
2) Listen for creaks, rubbing, or chain drops.
3) Do a few gentle stops to confirm braking feel.
4) Stop and re-check that nothing shifted.
5) Only then go on your normal route.
This turns “first ride” into a quick test instead of a long walk home.
Last checks before your first real ride
- [ ] All motor mounting hardware torqued
- [ ] Chainline acceptable (no rubbing)
- [ ] Brakes bedded and strong
- [ ] Cables secured and not rubbing
- [ ] Battery mount tight and stable
Troubleshooting (common issues and fast fixes)
| Symptom | Likely cause | Fix |
|---|---|---|
| Creaking under load | Motor not tight / lock rings loose | Re-torque to spec |
| Chain drops | Chainline off | Adjust spacers/chainring offset |
| Poor shifting | Indexing changed under new load | Re-index derailleur, check hanger |
| Random cut-outs | Loose connector or cable rub | Inspect connectors + secure cables |
| Excessive noise | Misaligned chainring / drivetrain wear | Check chain/cassette + alignment |
Safety and legal notes (US)
Many riders reference Class 1/2/3 behavior and <750W motor language when discussing rules. PeopleForBikes class overview
Where you can ride can vary. Some public lands use class-based access rules (example from NPS). NPS example
Related guides (same hub)
- How to Convert Your Regular Bike Into an E-Bike (Step-By-Step Guide)
- Common Mistakes When Converting Your Bike to Electric (and How to Avoid Them)
- Bafang Motor Conversion: What You Need to Know Before Installing
Official resources (worth bookmarking)
- Safety & charging basics: CPSC Micromobility Battery Charging Safety (2025)
- Battery fire risk example: CPSC warning on certain e-bike batteries (UPP, 2024)
- US class system overview: PeopleForBikes class definitions (1/2/3, <750W)
- Trail access example (NPS): NPS e-bike class definitions and access notes
- Certification context: UL Standards & Engagement overview (mentions UL 2849 tests)