Vivi ACE01 750W Torque-Sensor Fat-Tire E-Bike

The 30-second verdict

Under $1,000, e-bikes make one compromise almost universally: cadence-sensor pedal assist, which switches the motor on and off based on whether the cranks turn rather than how hard you push. The ACE01's headline is that it doesn't — Vivi fits a torque sensor, the component that makes assist ramp smoothly with rider effort, and pairs it with hydraulic 180 mm brakes and a 100 mm lockout fork that are each a tier above the price. We have not ridden this bike; every figure here comes from Vivi's published spec sheet, and the pattern-match to the identically-specced hardware on bikes we track closely is what gives us confidence in the picture. The honest caveats: 72 lb is heavy, the 60-mile range claim halves under arithmetic, and 25 mph assist makes it Class 3 with the path restrictions that carries. At $929.99 it is the best sub-$1,000 spec sheet in the catalogue today — the question is only whether a $460 M026SHUL does your actual riding for half the money.

The torque sensor is the story

On a cadence-sensor bike (every other sub-$1,000 fat bike we track, including the Kingbull Hunter 2.0 and Jasion EB5 MAX), assist is binary per assist level: cranks turning → full programmed power. On a torque-sensor bike, the controller reads how hard you press the pedals hundreds of times a second and scales the motor to match — assist feels like your own legs got stronger, starts are smooth rather than lurchy, and low-speed manoeuvring stops being an on/off exercise. The rest of the powertrain backs it up: 750W rated (the number state power caps regulate — legal everywhere; Oregon alone allows 1,000W), 1500W peak for bursts, and 90 Nm — the highest torque figure of any Vivi we track.

Range: 720 Wh is real capacity; 60 miles is not the real number

Vivi claims up to 60 miles. The arithmetic: 26x4.0" fat tires typically burn 20-30 Wh per mile under pedal assist, so 720 Wh ÷ 25 Wh/mi ≈ 29 miles of mixed riding — call it 25-35 depending on assist level, rider weight, and terrain, and less at a sustained 25 mph. Sixty miles requires ~12 Wh/mi, an eco-mode flat-ground figure. That said, 720 Wh is genuinely large — the same capacity as the ACE07 and Hunter 2.0 — and the semi-integrated pack is removable for indoor charging. The 3A fast charger (vs the 2A unit on cheaper Vivis) refills it in roughly 5-6 hours.

Speed and class

The configuration is textbook Class 3: pedal assist to 25 mph, half-twist throttle capped at 20 mph. Class 3 is the fastest street-legal class but carries real restrictions — several states bar it from shared-use paths, some mandate helmets for all riders, and seven states don't permit Class 3 sales as street-legal at all. If your state is one of them, the ACE07 — the same power platform capped at 19.8 mph as a Class 2 — is the compliant cousin. Check your state's page before ordering.

Build: hydraulics, lockout fork, and the certification line

Hydraulic disc brakes with 180 mm rotors are the right answer for a 72 lb bike that cruises at 25 mph — self-adjusting, strong in the wet, and the single biggest hardware gap between this and the cheaper Vivis' cable discs. The 100 mm suspension fork with lockout and preload adjustment is a real fork, not a pogo stick, though still coil-sprung. Shimano 7-speed, 26x4.0" all-terrain tires, and a 6061 aluminium frame with a 47.2" wheelbase round it out. Certification: SGS-tested UL 2849 and UL 2271 — the standards NYC Local Law 39 and California SB 1271 reference. Warranty is Vivi's standard 1 year on motor and battery — the spec is DTC-tier, the support model is not, and that's the honest trade at this price.

Who should buy it

Buy the ACE01 if you want the smoothest-riding fat bike under $1,000 — the torque sensor + hydraulics combination doesn't exist elsewhere at this price — and your riding mixes pavement, gravel, sand, or snow. Skip it if you need a step-through frame (the ACE07), live in a Class-3-restricted state (also the ACE07), want app features like GPS tracking (the ACE01 Pro adds them for $60), or your rides are short and flat enough that a $479.99 M026SHUL would do.