Retro Step-Through Electric Hybrid Bike
HKM-660691 Retro Electric Hybrid Bike
The HKM-660691 blends vintage step-through styling with a modern electric drivetrain: a 1000 W brushless rear hub motor (over 100 N.m of torque) and a 48 V 16.7 Ah lithium pack (801.6 Wh) in a high-strength steel retro frame. The 20 x 4.0 in fat tires soak up pavement and trail chatter, while hydraulic disc brakes front and rear bring it to a confident stop. Documented at up to 31 mph with a 19.3-37.3 mi range, it is equally at home on a city commute, a weekend trail loop, or an errand run - all with a look that turns heads at the cafe stop.
1000 W Rear Hub Motor48 V 16.7 Ah / 801.6 Wh Pack31 mph Top Speed20 x 4.0 in Fat TiresHydraulic Disc BrakesStep-Through Frame7-Speed Drivetrain265 lb Rider Capacity
Motor
1000 W
brushless rear hub, 100+ N.m
Battery
48 V 16.7 Ah
801.6 Wh removable lithium
Top Speed
31 mph
50 km/h, throttle only
Range
19-37 mi
31-60 km, varies with assist
Tires
20 x 4.0 in
Fat tread, all-terrain
Rider Capacity
265 lb
120 kg rider plus cargo
Overview
The HKM-660691 is built around a high-strength steel frame with retro step-through geometry. The low top tube makes mounting and dismounting easy for riders of any height or mobility, and the upright riding position keeps weight off the wrists on longer rides. The frame is rated for a rider-and-cargo load of 265 lb.
Under the bodywork is a 1000 W brushless rear hub motor that produces over 100 N.m of torque for standing starts and climbs, fed by a 48 V 16.7 Ah lithium pack storing 801.6 Wh of energy. A sine-wave controller meters power smoothly and quietly, and a 7-speed Shimano derailleur with 5 pedal-assist levels lets you add human power when you want to.
Real-world range is wide because the bike adapts to how you ride. Throttle-only at higher speed returns the lower end of the 19.3-37.3 mi band. Moderate pedal-assist on the same terrain regularly returns toward the upper end; optimal conditions have been measured at the full 37.3 mi. Cold weather, soft tires, headwinds, and steep terrain all reduce those numbers.
Comfort comes from the 20 x 4.0 in fat tires running at low pressure and the natural compliance of the steel frame, which absorbs road vibration that a rigid aluminum frame would transmit to the rider. The wide contact patch adds grip on sand, snow, gravel, and wet pavement, expanding where you can safely ride.
Key Features
1000 W Brushless Rear Hub Motor
A 1000 W brushless motor is laced into the rear hub and produces over 100 N.m of torque for confident hill starts and rapid acceleration. Direct drive means no chain wear on the motor side and a quiet, low-maintenance ride.
48 V 16.7 Ah Lithium Pack (801.6 Wh)
The pack lifts out of the frame with a key for indoor charging and stores 801.6 Wh - above the usual commuter budget. A full recharge takes about 5-7 hours on the supplied charger; partial top-ups take proportionally less. An integrated BMS guards against over-charge, over-discharge, short circuit, and thermal runaway.
Comfort Ride: Fat Tires and Steel Frame
The 20 x 4.0 in fat tires at low pressure and the natural flex of the steel frame combine to absorb pavement cracks, expansion joints, and trail chatter, so the rider arrives fresher than on a rigid frame.
Hydraulic Disc Brakes, Front and Rear
Front and rear hydraulic disc brakes (180 mm front / 160 mm rear rotor) give modulated, weather-proof stopping power. Levers with motor cut-off switches disable drive the instant either is pulled.
7-Speed Drivetrain
A 7-speed Shimano derailleur with a thumb shifter gives a broad gear range for efficient pedaling at any speed. The indexing is crisp and needs minimal adjustment over time.
20 x 4.0 in All-Terrain Fat Tires
The oversized casing provides stability, traction, and shock absorption on sand, snow, gravel, and pavement. Run them at 5-30 psi: higher for efficient pavement commuting, lower for soft surfaces.
Smart LCD Display with Backlight and USB
A bright backlit LCD shows speed, battery level, average and max speed, trip distance, odometer, and assist level. An auto-dimming backlight stays readable in sun and at night, and a USB port keeps a phone charged on the go.
Retro Step-Through with Cargo Ready Frame
The step-through geometry and sturdy steel frame make the bike easy to mount and stable under load. Optional racks and panniers turn it into a practical errand runner without changing its vintage character.
Full Specifications
Model
HKM-660691 | Retro Electric Hybrid Bike
Frame Material
High-strength steel, retro step-through geometry
Motor
1000 W brushless rear hub motor, 100+ N.m torque
System Voltage
48 V DC
Battery
48 V 16.7 Ah lithium-ion (801.6 Wh), removable and lockable
Charger
2 A smart charger, 100-240 V input
Charging Time
5-7 hours from empty
Battery Cycle Life
Approximately 800 charge cycles to 80 percent capacity
Top Speed
31 mph (50 km/h)
Range Per Charge
19.3-37.3 mi (31-60 km), varies with terrain, rider weight, and assist level
Climbing Grade
Capable on moderate to steep grades with pedal-assist
Peak Torque
100+ N.m (73.8 lb-ft)
Drivetrain
7-speed derailleur, thumb shifter
Brakes
Hydraulic disc brakes, 180 mm front / 160 mm rear, motor cut-off levers
Ride Comfort
20 x 4.0 in fat tires and steel frame compliance absorb vibration
Tires
20 x 4.0 in fat tires, all-terrain tread
Wheels
20 in alloy rims, stainless spokes
Saddle
Retro cruiser saddle with upright handlebar
Display
Backlit LCD with speed, battery, odometer, trip, USB port
Throttle
Twist-grip throttle with 5 pedal-assist levels and zero assist
Lighting
LED headlight provision, brake-activated tail-light, powered by main battery
Load Capacity
265 lb (120 kg) rider plus cargo
Bike Weight
Approximately 75 lb (34 kg) including battery
Recommended Rider Height
5 ft 1 in to 6 ft 3 in (155-190 cm)
Certifications
CE, RoHS; battery cells UN38.3 tested
Battery, Range, and Charging
The 48 V 16.7 Ah pack stores 801.6 Wh of energy. Most commuter e-bikes ship with 400-600 Wh, so this pack runs roughly 35-100 percent above the usual energy budget. That headroom is what lets the bike handle a throttle-only commute at 20 mph on flat pavement without range anxiety at the end of the work day.
Real-world range depends on how much you pedal, rider and cargo weight, tire pressure, and terrain. Throttle-only riding at higher speed lands in the 19.3-31 mi band. Moderate pedal-assist on the same terrain regularly returns 31-37 mi. Cold weather below 40 F (4 C) temporarily reduces available capacity by 10-20 percent; it returns once the pack warms up.
Tip: Store the pack between 30 and 70 percent charge if the bike will sit unused for more than a month, and top it up every 4-6 weeks. Charging indoors at room temperature extends usable pack life considerably compared with charging in an unheated garage.
The pack unlocks with the supplied key and lifts out of the frame in a few seconds, so you can charge it at a desk while the bike stays locked outside. Two keys are included. Charging with the pack installed works equally well - the charge port is accessible from the drive side.
Daily Use & Care
- Set tire pressure for the surface: 5-30 psi, higher for pavement commuting and lower for sand, snow, or gravel.
- Rinse the steel frame, rims, and drivetrain with fresh water after riding on salted roads or wet gravel to prevent corrosion.
- Check that both axle nuts and the stem bolts are torqued before the first ride of each week. Hub-motor torque works fasteners loose faster than on a conventional bicycle.
- Wipe and re-lubricate the chain every 100-150 mi, or after any ride through standing water or dusty conditions.
- Inspect hydraulic brake pads monthly. They wear silently; replace when the friction material is under 1 mm.
- Charge indoors at room temperature. Unplug the charger once the indicator turns green rather than leaving it connected for days.
- Keep the display and charge port covers closed when the bike is parked outside so moisture stays out of the connectors.
What's in the Box
- 1 x HKM-660691 retro electric hybrid bike, approximately 85 percent pre-assembled
- 1 x 48 V 16.7 Ah removable lithium battery pack
- 1 x 2 A smart charger with 100-240 V input
- 2 x Battery keys
- 1 x Toolkit with hex wrenches and pedal spanner
- 1 x Pair of folding pedals
- 1 x User manual and assembly guide
Frequently Asked Questions
How much assembly is required out of the box?+
The bike ships approximately 85 percent assembled. Remaining steps are fitting the front wheel, straightening and bolting the handlebar, installing the pedals and saddle, and checking brake alignment. Budget 30-45 minutes with the supplied tools. Have a bike shop check torque and brake bedding if you are not comfortable doing it yourself.
What is the actual range I should plan for?+
Plan for 19.3-37.3 mi depending on how much you pedal. Throttle-only riding at higher speeds lands closer to 19.3-31 mi. Moderate pedal-assist on mixed terrain regularly returns toward 37 mi. Heavier riders, headwinds, hills, and low tire pressure all reduce range.
Is a license or registration required?+
Rules vary by state and locality. A 1000 W motor with a 31 mph top speed exceeds the limits of the common three-class e-bike framework in many US jurisdictions, which may place this bike in a moped or motor-driven cycle category. Check your state DMV and local ordinances before riding on public roads or bike paths.
How long does the battery take to charge?+
About 5-7 hours from fully empty with the supplied 2 A charger. Partial top-ups take proportionally less time; there is no need to run the pack down before recharging.
Can I pedal it if the battery runs out?+
Yes. The 7-speed drivetrain works independently of the motor. The bike is around 75 lb, so pedaling home unassisted is slow going, but it is entirely possible on flat ground.
Will the brakes handle the speed?+
Hydraulic disc brakes front and rear are the right specification for a 31 mph bike. Bed the pads in during the first few rides with 10-15 progressive stops to build the friction layer on the rotors.
Is the battery removable for indoor charging?+
Yes. It unlocks with the supplied key and lifts out of the frame. You can also charge it in place through the frame-side charge port.
Can the fat tires handle snow and sand?+
Yes. The 20 x 4.0 in tires float on soft surfaces when run at low pressure. Drop to the lower end of the 5-30 psi range for sand and light snow, and raise it for efficient pavement commuting.
Service & Policies
Free Shipping on All Orders
Every order ships free. Handling Time: 0-1 business days (Monday to Friday). Transit Time: 2-5 business days (Monday to Friday). A tracking number is emailed as soon as the parcel leaves our warehouse.
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24 Months Warranty Service
The product is covered by a 24-month warranty from the delivery date against manufacturing defects. Coverage includes parts and labor; normal-wear items are excluded.
CERoHSUN38.3 Battery801.6 Wh PackHydraulic BrakesStep-Through Frame20 x 4.0 Fat Tires
Why Choose the HKM-660691
Retro Looks, Modern Drive
A vintage-inspired steel frame and cruiser saddle hide a genuine 1000 W motor and 801.6 Wh pack. You get head-turning style with the range and torque to back it up on real rides.
Fat Tires for Real Roads
Potholes, expansion joints, brick lanes, sand, and snow all become rideable surfaces when the wide, low-pressure tires absorb what a narrow tire would skip across.
Two Ways to Ride
Twist the throttle for immediate acceleration, or shift through the 7-speed cassette and pedal. Most owners mix both - throttle to get moving from a stop, pedals to extend the range, and motor for hills.
Direct-Drive Simplicity
The brushless rear hub has no mid-drive gearbox, belt, or extra chain to service. Fewer moving parts in the drive path means less to maintain and a notably quiet ride.
Step-Through for Every Rider
The low top tube and upright position make the bike easy to mount and kind to wrists and backs on longer rides. Fits riders from 5 ft 1 in to 6 ft 3 in.
Built for Daily Use, Not Just Weekends
Sealed electrical connectors, a covered and lockable battery compartment, and hydraulic lines that cannot corrode in road film make sense for a bike ridden to work every day and parked outside.
Controls & Indicators
Power Button
Located on the battery pack; hold to switch the system on and off
Mode Buttons
Up and down buttons on the display cycle through 5 pedal-assist levels plus zero assist
Twist Throttle
Right-hand grip; proportional response, works independently of pedal-assist level
Speedometer
Live speed readout in mph, switchable to km/h in the settings menu
Battery Gauge
5-segment charge indicator plus percentage readout on the color LCD
Light Switch
Long-press the up button to toggle the LED headlight and integrated brake light
Shifter
Right-hand thumb shifter for the 7-speed derailleur
Pre-Ride Safety Checklist
- Check tire pressure and set it for the surface: higher for pavement, lower for sand, snow, or gravel.
- Squeeze both brake levers. They should firm up well before reaching the grip, with no sponginess that would indicate air in the hydraulic line.
- Confirm the battery is seated and locked, and that the display shows the expected state of charge.
- Spin both wheels and check that the rims run true and nothing rubs the brake pads or the frame.
- Verify the axle nuts and stem bolts are tight, and that the headset has no play when you rock the bike with the front brake applied.
- Test the throttle at walking pace in a clear area before riding in traffic.
- Switch on the headlight and tail-light if you will be riding near dusk, and wear a helmet rated for the speeds this bike reaches.
- If carrying cargo, confirm any rack or panniers are secure and the load is balanced before you set off.
Quick Troubleshooting
The motor does not engage when I twist the throttle.+
Confirm the display is on and shows charge, the battery is locked into place, and both brake levers are fully released - brake cut-off sensors disable the motor while a lever is pulled. If the display shows an error code, note it and contact support.
Range dropped noticeably compared with when it was new.+
First check tire pressure; a soft tire on pavement is the most common cause. Then consider temperature - cold reduces available capacity temporarily. If range is down more than 30 percent year-round after many charge cycles, the pack may be approaching the end of its service life.
The brakes feel spongy at the lever.+
Sponginess in a hydraulic system usually means air in the line or a fluid leak. Stop riding and have the system bled and inspected. Do not continue riding a 31 mph bike on compromised brakes.
The chain skips under hard pedaling.+
The derailleur indexing is likely out of adjustment, or the chain and cassette are worn. Adjust the barrel adjuster a quarter turn at a time to align the indexing. If the chain skips only in the smallest cogs, the cassette is worn and should be replaced along with the chain.
The display shows an error code and the bike will not move.+
Power the system off, wait 30 seconds, and switch it back on. If the code returns, note the exact code and the conditions that produced it, then contact support - error codes map to specific faults in the controller, motor, or throttle circuits.
The bike feels harsh over bumps despite the fat tires.+
Confirm tire pressure is in the 5-30 psi range for the surface; over-inflated fat tires ride harsh. If the harshness persists, inspect the wheels and headset for play and have a shop check the frame.
Certifications & Standards
The HKM-660691 is produced in a facility operating under an ISO 9001 quality management system. The battery cells and the assembled pack carry the test documentation normally required for lithium-ion transport and sale.
- CE - European Conformity marking covering the electrical assembly.
- RoHS - Restriction of Hazardous Substances compliance for the electronics.
- UN38.3 - Battery transport safety testing, required for lithium-ion shipping by air, sea, and road.
- MSDS - Material Safety Data Sheet available for the battery pack on request.
- ISO 9001 - Quality management system certification held by the manufacturing facility.
Important Safety Notes
This is a high-output electric bicycle capable of 31 mph. Read the manual fully before the first ride and practice throttle control in an open, traffic-free area until the response feels predictable.
- Wear a helmet on every ride. At 31 mph a bicycle helmet is the minimum; many riders choose a certified motorcycle or downhill helmet at these speeds.
- Do not exceed the 265 lb (120 kg) load capacity, which includes the rider and cargo.
- Check local law before riding on public roads or paths. A 1000 W motor with 31 mph top speed may place this vehicle outside standard e-bike classifications in your area.
- Bed in the brake pads with 10-15 progressive stops during the first few rides before riding at full speed.
- Do not ride through water deep enough to reach the hub motor or the battery compartment.
- Charge only with the supplied charger, indoors, at room temperature, and on a non-flammable surface. Do not leave a charging battery unattended overnight.
- Do not attempt to open, puncture, or modify the battery pack. Damaged lithium packs can vent and ignite.
- Reduce speed substantially on gravel, wet surfaces, and downhill grades; fat tires add grip but do not eliminate the risk of losing traction.
HKM-660691 · 1000 W brushless rear hub motor (100+ N.m) · 48 V 16.7 Ah lithium (801.6 Wh) · 31 mph top speed · 19.3-37.3 mi range · 20 x 4.0 in fat tires · 265 lb (120 kg) rider capacity · steel step-through frame · hydraulic disc brakes · 7-speed drivetrain. Specifications are provided for reference; actual performance varies with rider weight, terrain, tire pressure, temperature, and riding style. Range figures are measured under moderate pedal-assist on level pavement. This page describes the product only and is not legal advice regarding vehicle classification - confirm local regulations before riding on public roads.
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