Aipas M1 Pro Xterrain ST Fat-Tire E-Bike

The average published payload across the bikes we review is 328 lb, and that figure has to cover the rider, clothing, a lock, a bag and anything on the rack. For a rider over about 250 lb it is the binding constraint, and only ten of the bikes we track publish 400 lb or more.

The M1 Pro states 500 lb, the highest figure in our catalogue — the next best are the TST City Commuter and SISIGAD Family at 450 lb. Paired with a step-through frame that removes the need to swing a leg over a top tube, 4-inch tires that spread load and absorb road shock, and a 110 Nm motor with enough torque to start a heavy load from rest on a hill, this is a coherent package for heavier riders rather than a spec-sheet boast. Our heavy riders guide covers the wider picture, and on payload alone this is the strongest bike in that conversation under $1,000.

The 88 lb bike weight is the price of that strength. This is not a bike to carry upstairs, and a car rack for it needs to be rated accordingly.

This is the comparison people actually search for, so here it is plainly. Vivi is the higher-volume brand on Amazon and sells more bikes at lower prices; Aipas sells fewer bikes at higher specifications.

• Battery: the M1 Pro's 840 Wh beats the Vivi ACE01 at $561.99 (as of Sep 25, 9:24 AM EDT, subject to change) and the Vivi ACE07 at $781.79 (as of Sep 25, 9:24 AM EDT, subject to change), both of which run smaller packs.
• Payload: 500 lb against Vivi's typical 330 lb. If you are a heavier rider, this is the whole decision.
• Certification: Aipas names SGS and UL 2271 for the battery. Vivi names UL 2849 on several models, which is the broader standard covering the whole electrical system — Vivi wins this one on scope.
• Torque sensor: the Vivi ACE01 uses a torque sensor, which meters assistance to how hard you pedal. The M1 Pro uses PAS levels, which switch power on in steps. The Vivi feels more natural on varied ground.
• Price: Vivi sits in the $400-600 range where most buyers land; the M1 Pro is $898.99 (as of Sep 25, 9:24 AM EDT, subject to change).

The short answer: buy the Aipas if you are heavy, carry loads, or want the bigger battery; buy the Vivi if you want UL 2849 on the whole bike, a torque sensor, or a lower price.

Aipas states SGS Certified to ANSI/CAN/UL 2271. Unpacking that: UL 2271 is the standard for the battery pack used in light electric vehicles; ANSI/CAN indicates the standard is harmonised for the US and Canada; SGS is the laboratory. That is a checkable claim.

What it does not cover is UL 2849, the standard for the complete e-bike electrical system — motor, controller, charger and battery together — and that is the one most US rules name first. New York City's Local Law 39 of 2023 bans the sale of e-bikes and batteries not certified to UL 2849 or UL 2271, so a UL 2271 battery satisfies the battery half of that rule. California's SB 1271 requires certification for e-bikes sold in the state from 1 January 2026. If your building asks specifically for UL 2849, this bike does not yet answer that question, and the Vivi C26UL or the Heybike Cityscape 2.0 at $609 (as of Sep 25, 9:24 AM EDT, subject to change) do.

48 V x 17.5 Ah is 840 Wh. An 88 lb fat bike carrying a heavier rider sits at the top of the normal consumption band, so 22-30 Wh per mile is the realistic range:

• 840 Wh / 30 Wh per mile = 28 miles (heavier rider, hills, higher assist)
• 840 Wh / 25 Wh per mile = 34 miles (our planning figure)
• 840 Wh / 22 Wh per mile = 38 miles (moderate assist on flat ground)
• 840 Wh / 85 miles = 9.9 Wh per mile, which is what the "up to 85 miles" claim requires

Under 10 Wh per mile is not achievable on an 88 lb bike with 4-inch tires, so the 85-mile claim fails its own arithmetic. Thirty-four miles is the number to plan around. Charging takes 4-6 hours per Aipas, and the pack can be charged on or off the bike, which matters if the bike lives in a shed and the battery comes inside.

Aipas recommends the bike for riders from 5'5" to 7'2", which is a tall range and confirms this is a full-size frame despite the step-through shape. Shorter riders should look at the Hopepeak D10 at $485 (as of Sep 25, 9:24 AM EDT, subject to change) instead.

The brakes are 180 mm mechanical discs, which is the one place the sheet disappoints given the weight involved: large rotors help, but cables stretch and pads need adjusting, and hydraulic brakes would suit a 500 lb rated load better. The Jasion EB5 Ultra at $799.99 (as of Sep 25, 9:24 AM EDT, subject to change) offers hydraulics for less money, with a smaller payload rating and no certification claim.

Everything else is sensible: a 7-speed drivetrain, 0-5 assist levels, a headlight, a brake-activated rear light, a horn, an LCD display with a USB charging port, and a claim that the bike arrives 90% pre-assembled with a toolkit. Aipas backs it with a one-year limited warranty and sells spare batteries, fenders and racks from its own storefront, which is a meaningful advantage over Amazon-only brands.

Buy this if you are a heavier rider or carry heavy loads, you want a certified battery from a named laboratory, and you value a brand with a real storefront and spare parts. Skip it if you need UL 2849 for the whole bike, if you want hydraulic brakes at this weight, or if you need a published top speed before you buy.