E-Bike Conversion Kit: 17 Must-Have Accessories & Upgrades

What Actually Happens Without One

• Chain skips under load during shifts, damaging cassette teeth
• Derailleur struggles to move chain while motor applies power
• Cassette lifespan drops from 3,000 miles to under 1,000 miles
• Chain replacement intervals cut in half

Installation Reality

• Mounts inline with rear derailleur cable
• Requires cable housing cut and sensor insertion
• Some versions require specific cable routing to avoid binding
• Bafang sensors work with Tongsheng motors and vice versa

Two Types Available

• Mechanical brake levers with built-in switches: Replace your existing levers entirely. Work with cable-actuated rim or disc brakes. Cheaper ($20-40 pair) but require complete lever replacement.
• Hydraulic brake sensors: Mount inline with hydraulic brake lines. Detect pressure changes when you brake. More expensive ($40-70 pair) but don’t require lever replacement.

The Compatibility Trap

Not all brake sensors work with all motor controllers. Bafang uses different connector types between BBS01b/BBS02b and BBSHD. Tongsheng TSDZ2b uses yet another connector. Verify connector compatibility before ordering or budget for adapters.

What Gets Damaged Without Protection

• Chainring teeth bend from direct rock strikes
• Aluminum chainrings crack under impact
• Motor mounting bolts shear when chainring catches obstacles
• Chain derails violently when bent teeth catch
• Chainring replacement costs $40-80 plus labor

Who Actually Needs Bash Guards

• Mountain bikers riding technical trails with rock gardens
• Riders who frequently encounter trail obstacles
• Anyone running large chainrings (48T+) that hang lower
• Urban riders navigating curbs and obstacles aggressively

Commuters on paved roads don’t need bash guards. They add weight and complexity without benefit on smooth surfaces.

When You Need a Stabilizer

• BBSHD motors programmed above 25A: High current creates massive torque
• Full-suspension frames: Frame flex amplifies motor movement
• Aggressive trail riding: Impacts and jumps stress motor mounts
• Bikes with worn bottom bracket shells: Loose fit allows motor rotation

Installation Reality

Stabilizer bars mount between the motor and frame, typically using existing bottle cage bosses. Not all frames have bosses in the right location. Some installations require custom fabrication or hose clamp mounts. BBS02 motors at conservative power levels rarely need stabilizers. BBSHD at 30A+ should always have one.

Important: Display upgrades only work within the same motor brand family. Bafang displays don’t work with Tongsheng motors without adapters. Some aftermarket displays claim universal compatibility but often lack full functionality.

What You Can Actually Change

• Current limits: Increase from conservative 15A to 25A+ for more power (at battery life cost)
• Speed limits: Raise or lower motor cutoff speed
• Pedal assist sensitivity: Adjust how quickly motor responds to pedaling
• Throttle response curve: Linear vs aggressive power delivery

The Programming Warning

Aggressive programming voids warranties and can fry controllers. Increasing current limits beyond what your battery’s BMS supports causes voltage sag, controller overheating, and shortened component life. Start with small changes and test thoroughly.

The Overheating Risk

Large chainrings (52T+) on BBS02B motors cause overheating on extended climbs. The motor lugs at low RPM, generating excessive heat. BBSHD handles large chainrings better due to superior cooling, but both benefit from appropriate gearing for intended use.

Open Source Firmware Benefits

• Smooth power delivery from 0-120 RPM cadence (factory cuts at 90 RPM)
• Responsive throttle (factory has ~1 second lag)
• Customizable power curves per assist level
• Walk assist actually works properly
• Temperature monitoring and protection

The Installation Reality

Flashing open source firmware requires opening the motor casing, connecting a programmer to the controller board, and running software on your computer. It voids warranties. Some sellers offer pre-flashed motors for $50-100 premium. For DIY types, the upgrade takes 1-2 hours and costs around $30 for the ST-Link programmer.

When Nylon Gears Fail

• Heavy riders (200+ lbs) see failure around 2,000-3,000 miles
• Cargo bikes or trailer hauling accelerate wear significantly
• Steep climbs at high assist levels increase stress on gears
• TSDZ8 models include metal gears from factory

Metal Gear Upgrade

Aftermarket metal reduction gears cost $40-70 and essentially eliminate this failure point. Installation requires motor disassembly (45-90 minutes). Some riders preemptively upgrade before the nylon gear fails. Others wait for failure and rebuild with metal components.

The Adapter Solution

Generic shift sensors work with simple wire splicing or using adapter cables. Most Tongsheng kit sellers include compatible sensors. If buying separately, verify connector type or plan for minor wiring modifications.

What Happens Without Torque Arms

• Motor axle slowly rotates in dropouts under power
• Dropout slots elongate and widen from repeated stress
• Eventually axle spins completely, ripping motor cable from controller
• On aluminum frames, dropouts crack rather than bend
• Front fork failures at speed are especially dangerous

Real Failure Stories

Dropout failures happen suddenly, not gradually. You’re riding normally, hit the throttle or pedal hard, and the axle rotates 90 degrees instantly. Motor cable rips out, wheel shifts, and you’re fighting for control. On front hubs, this means crash. Always use torque arms rated for your motor’s power level.

Installation Types

• Hose clamp mount: Simple but can slip on smooth frame tubes. Works okay for rear motors under 500W. Not recommended for front motors.
• Bolt-through frame mount: Most secure option. Requires drilling frame or using existing bottle cage bosses. Best for high-power installations.
• Integrated torque arms: Some aftermarket hub motors include built-in torque arm features. Still recommend supplementary external arms for 750W+ motors.

Critical Reminder: For 1000W+ motors or front hub installations on aluminum frames, use TWO torque arms (one on each side). Single torque arms can fail under extreme torque. Budget $30-60 for quality torque arms versus $300-800 for frame replacement.

Why Stock Brakes Fail

• Kinetic energy increases with the square of velocity (2x speed = 4x braking energy)
• E-bikes weigh 50-70 lbs vs 25-30 lbs for regular bikes
• 160mm rotors can’t dissipate heat fast enough at sustained high speeds
• Brake fade on descents becomes dangerous when motor adds weight
• Hydraulic fluid boils under extreme heat, causing complete brake failure

Rotor Size Recommendations

• 250-500W, under 45 lbs total: 180mm front, 160-180mm rear acceptable
• 500-750W, 45-60 lbs total: 180mm front minimum, 180mm rear recommended
• 750W+, 60+ lbs total: 203mm front mandatory, 180-203mm rear required
• Cargo or tandem e-bikes: 203mm front and rear, no exceptions

The Adapter Requirement

Upgrading rotor size requires mounting adapters. Front fork and rear frame have specific mounts (post mount or flat mount). Going from 160mm to 180mm needs a 20mm adapter, 160mm to 203mm needs 43mm adapter. Not all frames accept adapters due to clearance issues. Verify compatibility before ordering.

Common Sensor Problems

• Magnet loosens and falls off spoke during riding
• Sensor mounting location interferes with fenders or rack
• Gap between sensor and magnet exceeds 5mm, causing intermittent readings
• Sensor cable routing causes it to snag on obstacles

Upgrade Options

Zip-tie magnet mounts fail quickly. Use threadlock on screw-mount magnets or upgrade to stronger adhesive-backed magnets. Consider purchasing spare sensors and magnets ($5-10) as backup. These components fail more often than any other part of the conversion.

The Voltage Sag Problem

Increasing controller amperage to 35A+ requires batteries with high-discharge capability. Cheap batteries with 30A BMS limits will shut down or sag voltage dramatically under high current draw. This causes stuttering power delivery and shortened battery lifespan. Match controller upgrades with appropriate battery capacity.

Common PAS Sensor Failures

• Magnet disc loosens on crank arm, losing sensor alignment
• Water ingress damages sensor electronics
• Sensor mounting bracket cracks from vibration
• Incorrect gap between sensor and magnet causes intermittent assist

When to Upgrade Controllers

• Original controller failed: Common after 2-3 years of heavy use or water damage
• Upgrading from BBS02 to BBSHD power: Requires higher-amp controller
• Adding features: Some aftermarket controllers offer regenerative braking or advanced programming
• Improving heat management: Upgraded controllers with better MOSFETs handle heat more efficiently

What Cycle Analyst Actually Shows

• Real-time power consumption: Watts being drawn from battery, not generic “assist levels”
• Precise voltage monitoring: Battery voltage to 0.01V accuracy, reveals battery health
• Amp-hours consumed: Track exactly how much capacity you’ve used
• Watt-hours per mile: Efficiency data for route planning
• Peak current tracking: See maximum amps during hard acceleration
• Temperature monitoring: Optional probes track motor and controller temps
• Trip data: Distance, average speed, time, max speed

Why Power Users Love It

• Diagnose battery problems by tracking voltage sag under load
• Optimize riding style for maximum range using real-time efficiency data
• Program throttle/pedal limits based on actual amp draw
• Identify controller issues by monitoring current delivery
• Data logging for analyzing ride performance

The Downsides

• Expensive: $150-180 for the unit alone, more with accessories
• Complex installation: Requires shunt resistor in power line, precise wiring
• Not plug-and-play: Works with any system but needs proper integration
• Information overload: Too much data for casual riders
• Screen size: Small monochrome display packs in lots of numbers

Who Actually Benefits

Cycle Analyst makes sense for DIY builders, performance tuners, long-distance tourers, and anyone troubleshooting system issues. If you just want to ride and don’t care about voltage curves or watt-hours per mile, skip it. The $150-180 cost only pays off if you use the data to optimize performance or diagnose problems.

Alternative Option: Some high-end displays like the Bafang 750C or Eggrider offer basic watt and voltage monitoring without the Cycle Analyst’s price tag. For most riders, these provide sufficient data at $60-100 versus $150-180.

Skip These

• Cheap phone mounts: Vibrations destroy phone internal components over time. Use dedicated GPS units or put phone in pocket.
• Battery range extenders: Carrying a second battery in a backpack works better than expensive parallel wiring setups. Less complexity, more flexibility.
• Motor covers/guards: Add weight and trap heat. Mid-drives already have adequate protection. Money better spent elsewhere.
• Suspension seatposts (low-end): Sub-$50 suspension seatposts add dead weight and offer minimal comfort improvement. Save for quality suspension or skip entirely.
• Generic “e-bike” specific locks: Same locks as regular bikes but marked up 30-50%. Buy quality U-locks regardless of branding.