AIMA Big Sur Fat Tire Electric Bike Review
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AIMA Big Sur Fat Tire Electric Bike Review

AIMA Big Sur with rider on street
  • AIMA Big Sur e-bike price tag is $1799
  • Has a Torque Sensor
  • Really fun to ride with a good battery range
  • Heavy, at 82lbs

AIMA is a brand that no one in the U.S. had likely heard of until they brought over their first bikes to the Electrify Expo in Long Beach this year. They’re no startup, they’re a massive micromobility producer in China, who manufactured and sold 12 million units last year. The company did a lot of research on the American market and decided that an electric fat bike would be their first product to sell here. 

They named it after the northern California coastline, calling it Big Sur, to conjure up visions of adventure. I asked them to send me one to review, and they obliged.

The Bike

If you order the AIMA Big Sur shipped to you, it comes partially assembled in a massive crate that weighs in at around 100 lbs. I was happy that the two guys who delivered it carried it all the way into my place. Unboxing took a while, and since I currently don’t have a bike stand that can hold an 82 lb bike, I had to have my magnificent other help me. 

That’s right, I said 82 lbs. That is significant, because I live in an apartment, and have to bring the bikes up stairs to keep them safe while I work on reviews. Electric fat bikes are generally heavy, but this one is 5 lbs heavier than its sped-for-spec rival, the Aventon Aventure.2

The Big Sur is available only in a step-through frame, in your choice of Ivory White or Matte Black. 

The Parts

The Big Sur comes with a lot of creature comforts. It has a massive, padded seat, a bolted-on rear rack that can handle up to 60 lbs of cargo, integrated front and rear lighting, a suspension fork, and fenders. It’s all well laid out with controls where you’d expect them. Cable routing is mostly internal.

The bolted-on rear rack can handle up to 60 lbs of cargo.

The lighting is bright, the big front headlight will get you noticed day or night, and the rear light lights up brighter as a brake light. The brake levers have cutoff switches that immediately cut power to the motor when you start to apply the brakes.

The Motor

AIMA went with a 750W Bafang rear hub drive to move this monster. There’s no shortage of power there, it’s the most power you can legally have in most states. It’s a Class 3 bike, meaning it will give you pedal-assist power at speeds up to 28 mph, and it has a throttle that can get you up to 20 mph. 

Now, here’s the most important part of the motor’s story. This bike is equipped with a torque sensor. What on earth is a torque sensor, and why do you want it? Let’s first look at what most bikes in this price range usually use, a cadence sensor. This sensor, normally located near the cranks/bottom bracket area, notices when you are turning the cranks. It doesn’t matter if you’re putting in any effort at all, if you’re turning the cranks (pedaling), you’re getting all the power that whatever mode you are in can give you. For example, if you’re in mode 1, you’ll be whisked off instantly to about 12 mph, often abruptly. Mode 2 will get you to 15 mph, and so on.

With a torque sensor, you get power when you are putting in more effort. In general, you get more power when you put in more effort on your own. AIMA has something a little different here, when you pedal, the torque sensor will give you power if you pedal hard enough, but it doesn’t seem to give you more if you pedal harder. It does feel more efficient, though, with the torque sensor. 

In this bike, they put the torque sensor, motor controller in the bottom bracket area, so it looks almost like the bike has a mid-drive. It does not.

The battery is a massive 720Wh unit made of LG 21700 cells. It’s handy to be able to take the battery out, technically I have to remove the battery and the 5 lb seat/seatpost combo to make the bike lighter enough to go on my bike rack to take it places. AIMA claims it will do “up to” 60 miles. <sarcasm>As always, that’s figured using a 110 lb rider on completely flat terrain using the lowest assist mode and having a slight tailwind. </sarcasm> 

In my rides, it did seem there would be no range anxiety. It does offer plenty of range for any ride I wanted to do. I’d say that for most average riders, 30-40 miles is possible on one charge. 

The display is centered over the stem, full color, with speed, mode, and battery information all right there. It’s plenty bright even for full sunlight in the middle of the day. The controls are on the left side of the handlebar, with two buttons to change modes up or down, and the throttle to the left of that.

The motor controls are neat and tidy on the left side of the handlebar.

The motor system did earn its UL 2849 rating just as it arrived in the U.S. to provide additional peace of mind about the electrical system.

Who It’s Made For

As a Class 3 e-bike with a sturdy cargo rack, the Big Sur is a very capable commuter, and would also be good for bikepacking. The fat tires make it capable of traversing almost any terrain. The high volume of the tires means that they provide some of the suspension (there is a short-travel fork), but also by varying the pressure they work well on surfaces from smooth pavement (high pressure for low rolling resistance) to sand or snow (low pressure for more grip). 

The Ride

I’ve already complained about the weight. Now let’s talk about the actual ride quality. The power kicks in right away but feels very natural. It’s very easy to get going and stay going.

There are 5 different levels/modes of power. I like a lot of power, I’m often using the higher end of the available power, so I’d normally be at level 4 or 5 most of the time, because why not? I found that I kept the Big Sur in level 2 almost all the time. It has a nice 8-speed Shimano Altus drivetrain with trigger shifters which gave me plenty of range. I’d occasionally bump the level up on steep hills. 

Once this thing gets going, it’s like a juggernaut. Absolute fun on two wheels, it is really one of the most fun commuter-ish bikes I’ve been on in a while. Bumps, cracks, grates, roots, nothing bothers the 4-inch tires. Riding it down stairs is an absolute blast! I seriously enjoyed every trip I took on it.

The Tektro hydraulic disc brakes work pretty well. They outfitted the front and rear with 203mm rotors, much better leverage than 180mm, though I’d rather have a quad-piston brake on the front for just a bit more stopping power and modulation.

I understand where they were going with the ginormous seat, but I’d probably replace it with something lighter that fits me better. It’s just so big and heavy.

To get action shots, I employed my friend to ride it while I photographed him. He did not want to give it back, he had so much fun. I let him take it on a few more errands before he brought it back. 

The Verdict

If you want a fun-to-ride, affordable, very sturdy fat bike, this is worth a test ride. They can ship directly to you, or you can find a local dealer from their website. Buying from a dealer will offer you professional final assembly and of course the ability to test ride the bike first. Keep in mind the weight of this bike and where you will keep it. If you have a garage, that’s perfect. 

AIMA’s Big Sur Specs

Frame6061 single-butted aluminum alloy
ForkSuspension fork with 80mm travel
MotorBafang 750W, 48V brushless rear hub motor
BatteryRemovable internal Lithium-ion, 720Wh with LG 21700 cells
ControlsFull-color LCD display
Charge Time5 hours
Top Speed28 mph
RangeUp to 60 miles (claimed)
Rear derailleurShimano, 8-speed
BrakesHydraulic disc brakes
SaddleAIMA Comfort
RimsDouble wall aluminum
HubsFront aluminum alloy disc hub
TiresPuncture resistant 26×4”
Weight82 lbs
Color ChoiceMatte black or Ivory white
SizesOne size (fits 5’1” to 6’4”)



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One Response

  1. After you do a review, who is responsible for the shipping to send said e-bike back? I have been a e-bike enthusiast for approximately 7 years. It all started with a Raleigh Cabent really awesome bike craftsmanship is second to none. I have 2 others that I also ride I choose based on what I’ll be doing that day.I live in the northeast with all 4 seasons and all my bikes do all fours seasons .I would thoroughly enjoy reviewing some of these bikes to help people better understand which ones do what. Thanks for your excellent review. Hard to believe just 7 years ago just me and another fellow were the only ones to have e-bikes here in my town now they are everywhere.

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