HKM-3429587 Retro Fat Tire E-Bike Runs a 1500W Hub on Cast 20 x 4.0 Wheels With a Bench Seat and a Fold for Off-Road

1500W · 960Wh · 34 to 40 mi · 20 in · cast wheels · hydraulic discs · 7-speed · NFC unlock · folding frame

Cast Wheels a Bench Seat and a Number Plate on the FrameRetro Soul With Real Modern Muscle

A 20-inch retro fat bike with a 1500W peak rear hub, 50 Nm of torque and a 48V 20Ah pack worth 960Wh in the down tube. Cast alloy wheels carry 20 x 4.0 knobby tires, an inverted double-crown fork and a rear coil shock handle the rough ground, and dual hydraulic discs do the stopping. There is a seven-speed cassette, NFC unlock, a round grille headlight with turn signals, a bench seat and a fold for storage. It is listed at 34 to 40 miles and it rides like a small motorbike rather than a mountain bike.

The look is doing a lot of the work here, and it is deliberate: a bench seat rather than a saddle on a post, a round grille lamp, a side plate where a race number would go, and one-piece cast wheels. Very little in this range bothers with a coherent retro theme, and the black-on-black finish is what keeps it from becoming a novelty. The bench changes who buys it: you sit on it rather than over it.

Underneath that it is a 20-inch fat bike with a long wheelbase, a 960Wh pack in the frame and suspension at both ends. That is the honest description: it is not a trail bike in the mountain-bike sense, but it does have the travel and the tire volume to make a fire road or a packed beach into a comfortable ride rather than an endurance test, and the seven-speed cassette lets you turn the pedals on a grade instead of letting the motor do everything.

At a Glance

• Peak 1500W Hub — 50 Nm, 35 degree climb
• 48V 20Ah Pack — 960Wh inside the down tube
• 34 to 40 Miles — Listed range, 8 to 10 hour charge
• 25 mph Listed — Poster figure, page says to 37
• 7-Speed Drive — Cassette behind the hub motor
• Hydraulic Discs — Dual, front and rear
• Full Suspension — Inverted fork, rear coil shock
• Cast Alloy Wheels — 20 x 4.0 knobby, no spokes
• NFC Unlock — Card or key, PAS 1 to 5
• Retro Bench Seat — Moped length, fixed
• Folds — For storage, not for a train
• Round Grille Lamp — With turn signals and horn

Retro Body and Cast Wheels

The frame is a moped shape in black, with a long bench over the rear wheel and a battery tucked into the down tube. A side plate sits where a race number would go on a flat-track bike, and the round grille headlight finishes the look.

The wheels are cast alloy in one piece, which is the detail that separates this from a generic fat bike. There is no spoke tension to check, nothing to go out of true at the low pressures a four-inch casing wants, and the bead seat holds better when you drop to 8 psi in sand.

Suspension is at both ends: an inverted double-crown fork up front and a pair of coil shocks under the rear of the frame. On 20-inch wheels with four inches of tire that is enough to keep the bike from skipping across a washboard track, which is the sort of surface this bike is actually bought for.

• Frame: moped shape, black
• Battery: 48V 20Ah, down tube
• Wheels: cast alloy, 20 in
• Fork: inverted, double crown
• Rear: coil shock
• Brakes: hydraulic disc, both ends

Fitted as shipped: front and rear fenders, a flat rear rack, the round grille headlight, a small bar bag, a kickstand and the battery keys. Braking is dual hydraulic discs, front and rear, with the hose routed down the fork leg and a motor cut-off at each lever. The bars carry the turn signals, the horn button and the NFC reader, and the pedals are platform type with reflectors.

1500W Hub and the Listed Range

Peak power is 1500W from a single brushless rear hub, with 50 Nm of torque and a listed 35 degree climb. One motor keeps the steering light and leaves one controller to look after, and because it turns a cast 20-inch wheel the torque reaches the tire with less loss than the same unit would manage on a larger rim. The seven-speed cassette behind it means you pedal with the motor rather than against it.

The pack is 48V 20Ah, which works out at 960Wh, and it sits inside the down tube behind a key-locked cover. A full charge runs 8 to 10 hours on the supplied charger through a sealed port, so the bike comes indoors rather than the battery. The poster claims up to 65 miles; plan on 34 to 40, because that larger figure assumes a light rider, flat ground and the lowest assist level.

Top speed is listed as 25 mph on the poster and 25 to 37 mph on the product page, and the gap matters. 25 mph is already the Class 3 ceiling in the US; 37 mph is a downwind, full-throttle number that no state allows on a public path. Ride it on private ground or a trail where the limit does not apply, and check local rules before using the top of that range anywhere else.

Who It Fits and How It Rides

The bench is fixed rather than on a post, so the fit range is narrower than the frame suggests: about 5 ft 4 in to 6 ft 2 in. Taller riders will feel their knees come up and shorter riders will find the step-in easier than a saddle bike, so sit on one before ordering rather than assuming.

On gravel, packed sand and broken pavement it is stable and the rear coil shock keeps the bench level. On a smooth road the knobby tread hums and the steering is slow, which is the trade for the tire volume that makes the rough surfaces work. The hydraulic discs want a firm two-finger pull rather than a grab, and they stay consistent when the rims are wet or gritty.

• Fire roads, farm tracks and packed dirt
• Beach towns and campgrounds
• Storage where a full-size fat bike will not fit
• Not for tight singletrack, stairs or public roads at the top speed

What's in the Box

Before the first ride: check the fold joint is fully seated, check both axles, set the fork and shock preload for your weight, bed the disc brakes in with ten firm stops from a walking start, then charge the pack. There are no spokes to tension, so put that time into the brakes.

Color and Finish

Black covers the frame, fork lowers, fenders, rack, rim faces and the bench, with the number plate picked out in white and the only other colour coming from the orange reflectors on the pedals. It is the most monotone bike in this range, and the retro shapes carry it rather than graphics.

Touch-up paint in matte black is available on request. The wear points are the bench edges, the cast wheel faces and the chainstay under the chain.

Battery Care and Maintenance

Charge the pack between 20 and 90 percent for daily use and take it to full about once a month so the management system can balance the cells. Because the pack lives inside the down tube, the ride home from a cold day should end with the bike indoors rather than in a freezing garage.

Check tire pressure before every ride at 15 to 20 psi on pavement and 8 to 12 psi on sand, and check both axles and the shock preload after the first 50 miles. Check the hydraulic pads monthly and the hose fittings for seepage, keep the charge port covered, and wipe the cast wheels after a wet ride. The NFC card is a convenience rather than an alarm, so park it where you would park a motorbike.

Specifications

Frequently Asked Questions

Service and Policies

Coverage that lasts beyond the box. Orders ship free with a tracking number in 2 to 5 business days. From delivery, the product is protected for 180 days against manufacturing defects and transit damage, returnable within 30 days for a full refund, and covered by a 24-month parts-and-labor warranty on manufacturing defects. Four policies, one idea: ship it free, protect it for 180 days, take it back for 30, and stand behind it for two years.

HKM-3429587 · retro 20 in fat tire electric bike · peak 1500W brushless rear hub, 50 Nm, 35 degree climb · 48V 20Ah 960Wh pack in the down tube, key-locked · 34 to 40 miles listed range · 25 mph listed, up to 37 mph on the page · dual hydraulic disc brakes with motor cut-off · inverted double-crown fork with a rear coil shock · cast alloy 20 x 4.0 wheels with no spokes to true · seven-speed cassette · NFC unlock, PAS 1 to 5 and a cruise mode · round grille headlight with turn signals and a horn · retro bench seat · flat rear rack · front and rear fenders · white number plate on the frame · folds for storage · matte black · charger and NFC card in the box · UL listed · built for fire roads, beach towns and campgrounds rather than tight singletrack, stairs or public roads at the top speed