Ebike Oracle

Review · TST

mountain7.0/10

TST Fat Retro

By John WeeksUpdated Jul 27, 2026How we score

Spec-verified against the manufacturer listing

Our verdict

7.0
/ 10

The TST Fat Retro, Amazon's #2 best-selling electric fat bike (September 2026), claims 2000W peak, 90 N·m and dual suspension for $579.99 (as of Oct 14, 5:10 PM EDT, subject to change), but states neither a rated wattage nor a top speed. Those are the two numbers that decide where you may legally ride it, so the three-class system cannot place this bike from the listing alone. If cushion per dollar is the brief it earns the look; if paperwork matters more, TST's own Fat 20 prints its 750W rated figure at $549.99 (as of Oct 14, 5:10 PM EDT, subject to change).

Best for
Gravel-and-towpath riders who value cushion over paperwork

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TST Fat Retro

At a glance

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Battery
720Wh
Range
32mi

The numbers

TST Fat Retro is a electric mountain bike that scores 7.0/10 on our editorial rubric, last verified on July 27, 2026. Amazon listed it at $580 as of October 14, 2026. Prices change often, so treat that as a snapshot. On Amazon it currently ranks #1 Best Seller in Electric Fat Bikes. It pairs a 720 Wh battery, good for a claimed range of up to 32 miles. It best suits gravel-and-towpath riders who value cushion over paperwork.

Pros

  • + Amazon's #2 Electric Fat Bikes best seller (September 2026), so a huge field population
  • + Claimed 90 N·m torque, unusually high for the price if accurate
  • + Dual suspension + 20"×4" tires: the comfort-maximal budget format
  • + Removable ~720Wh battery with LCD and smartphone app
  • + $579.99 (as of Oct 14, 5:10 PM EDT, subject to change) for dual suspension plus fat tires still undercuts most of that format

Cons

  • - Rated wattage undisclosed: only "2000W peak" is stated, which no statute recognises
  • - Top speed unstated, so its legal class cannot be determined from the listing
  • - Battery voltage unstated ("15AH" alone), so capacity is our arithmetic, not their spec
  • - No UL 2849 or UL 2271 certification mentioned
  • - 180-day warranty, half the usual one year

Who is this for?

  • Gravel-and-towpath riders who value cushion over paperwork
  • Buyers comfortable verifying the speed cap and wattage plate on arrival
  • Anyone chasing the most suspension per dollar on Amazon

The 30-second verdict

This is one of the two retro fat bikes that own Amazon's fat-tire category: #2 in Electric Fat Bikes in September 2026, behind only the Jasion RetroVolt 330, and it was #1 for most of the summer. The hardware list explains the volume: dual suspension, 20"x4" rubber, a claimed 90 N·m of torque and smartphone-app connectivity for $579.99 (as of Oct 14, 5:10 PM EDT, subject to change). Our reservation is disclosure, not hardware. The listing quotes peak wattage only (2000W) and no top speed, so you cannot place it in the three-class system from the listing alone. TST proves on its own Fat 20 and City Commuter that it can publish rated figures; here it chose not to. The claimed 90 N·m would out-pull bikes at twice the price if the number holds, the app is a genuine rarity at this price, and the removable pack means charging happens wherever the sockets are rather than wherever the bike sleeps. No UL 2849 or UL 2271 certification is named anywhere on the listing.

The full review, section by section. Tap any section to read it.

The peak-wattage problem, plainly

US e-bike law regulates rated (continuous) wattage: the federal definition at 15 U.S.C. § 2085 sets 750W, every state but Oregon copies that ceiling, and no statute mentions peak. A "2000W peak" bike may carry a perfectly legal 750W rated motor, or it may not; without the number, a path ranger or an insurer gets to guess. That's why our spec table shows rated wattage as blank rather than repeating the marketing figure. Amazon sells this frame under several listings, and one of them quotes 1500W peak for what is visibly the same bike, which tells you how loosely the headline number is used. If the class question decides path access where you live, start from our class explainer and ask the seller for the rated figure before buying.

Battery, range, and an assumed voltage

The listing says "15AH" and never names the voltage. Every credible bike in this bracket runs 48V, which would make ~720Wh, a big pack for the money and the basis of the 65-mile claim. Sixty-five miles from 720Wh needs 720 ÷ 65 ≈ 11 Wh per mile, and a 4-inch fat tire with an upright rider draws closer to 20. By that arithmetic, mixed riding at about 20 Wh per mile would land nearer 30-35 miles. The pack is removable, and the LCD-plus-smartphone-app combination is unusual at this price.

Ride hardware

Dual suspension plus fat tires is the plushest configuration a budget frame can offer, and on gravel, towpaths and beaten-up streets it's the right one. The listing does not say what kind of fork or rear shock it uses, what type of disc brakes it carries, or what the bike weighs, so treat all three as unknown until it arrives. The 7-speed drivetrain and 5 assist levels are standard for the class. The warranty is 180 days, half the one-year norm.

Who should buy it, and the alternatives

If you want maximum cushion for unpaved-path riding and you're comfortable confirming the speed cap yourself on arrival, its sales rank says plenty of buyers already decided yes. The closest rival is the Jasion RetroVolt 330 at $539.99 (as of Oct 14, 5:10 PM EDT, subject to change): the same moped-style format, a claimed 99 N·m, and currently the better seller. If disclosure is what you care about, stay inside TST's range: the Fat 20 prints 750W rated alongside its peak figure, a 450 lb load rating and a published weight, which settles the federal 750W rated-wattage question on paper.

TST Fat Retro

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Frequently asked questions

What class is the TST Fat Retro?

It cannot be determined from the listing: the seller states neither rated wattage nor top speed, and those two numbers define the three-class system. If it arrives limited to 20 mph with a legal rated plate it will ride as Class 2. Confirm on the motor's rating plate and the display settings, then check your state's rules.

Why does your spec table leave wattage blank when the title says 2000W?

2000W is the peak figure, the momentary maximum under load, and another listing for the same frame says 1500W. Statutes regulate rated (continuous) wattage, which the seller does not disclose. We record what is stated, not what marketing implies. (For the record: Oregon is the only 1,000W state, and everywhere else caps at 750W.)

How fast does the TST Fat Retro go?

The listing does not state a top speed, so we leave it blank rather than guess. A 2000W peak motor on 20"x4" tires is built to go well past 20 mph, which is where Class 2 stops. Check the speed limit in the display settings when it arrives: set to 20 mph, it stays inside the Class 2 speed rule, although the missing rated wattage figure still leaves its class open.

Is 65 miles of range believable?

As a best case on the lowest assist on flat ground, barely: it needs about 11 Wh per mile from a ~720Wh pack. With 4"-wide tires and a 90 N·m motor, our arithmetic puts mixed riding at about 30-35 miles. Strong for the money; just not 65.

TST Fat Retro or Jasion RetroVolt 330?

They are the same idea: moped-style frame, 20"x4" tires, dual suspension, a padded bench. The RetroVolt 330 is currently the bigger seller and costs $539.99 (as of Oct 14, 5:10 PM EDT, subject to change) against $579.99 (as of Oct 14, 5:10 PM EDT, subject to change) here; neither publishes a rated wattage. If you want the wattage question settled on paper, look at TST's Fat 20 instead, which prints 750W rated.

TST Fat Retro

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