The lower-priced, stealth electric bike

Thanks to a stack of gears and the rear derailleur, most people rarely notice the larger rear hub that contains the electric motor of a rear hub-drive e-bike. The most noticeable indicator that it has electric power assist is the visible battery package mounted on the downtube, rear rack or somewhere else on the bike. If the battery is somehow molded into the bike’s design, then it appears that you may be riding just a regular bicycle. The Espin Flow falls into that stealthy category.

So, where is the battery on this bike? It’s cleverly disguised into the bike’s downtube. You’ll notice that it’s a little bigger than normal, which seems logical since their is no horizontal top tube from the seatstay to the steering tube. The aluminum frame is open on the left side, and a long, skinny battery fills the area, looking exactly the same as the other side. Espin didn’t invent this concept. There are some other e-bikes that have their battery molded into the downtube, too, with Easy Motion being the best-known brand for the style.


The Espin weighs in at 46 pounds, which is respectable for an electric bike. The electric assist is provided by a 350-watt hub motor, which is a step up from a 250-watt motor that is common in many lower-priced e-bikes. The 36-volt battery has 11.6 amp-hours with 418-watt hours and is put together using numerous Panasonic lithium-ion cells, which is pretty much the industry standard.

For its componentry, the Espin relies on a Shimano Acera Rapid Fire eight-speed drivetrain, with a single chainring up front and eight cogs in back. Tektro Novela mechanical disc brakes are front and rear with 160mm rotors. There is no rear suspension, but you do get SR Suntour Nex suspension forks on the front.

An electric bike needs a display, and the Espin Flow has an LCD multifunction unit facing you from the middle of the handlebars. A wire goes from it to a switch on the left end of the handlebars, which is within easy reach of your thumb. You click up or down for more or less electric assist, and you can also switch to different screen displays—trip meter, time, top speed and current speed. In constant view is your current speed and battery level. Five bars means fully charged, and then it drops to four bars, three bars and downward as you travel more miles.


Okay, so what is a typical ride for you? Do you normally ride with a group of friends on standard bikes? If so, you’ll fit right in with them on the Flow. It looks pretty much like normal bikes and doesn’t stand out as being that different. The people you ride with may not even realize you’re on an electric-assist bike unless you tell them.

Perhaps you like to ride with your significant other, but on a normal bike you have trouble keeping up. On the Flow, you’ll be able to. One of our  test riders has a normal cruising speed of 12 mph on her regular bike. With the Flow set at power-assist level 3, she cruised it at 16 mph and could go around 10 miles further before she got too tired. There are five levels of assist, and at level 4, she could pedal at 18 mph, and at level 5 she could maintain 20 mph. We didn’t spend much time riding at levels 1 and 2, because it just didn’t seem to be as much fun.

Espin claims the Flow will go 25 to 50 miles on a full charge. That seems to be accurate based on our test rides. We normally pedaled in levels 4 and 5, and each of the five bars was worth five miles on flat roads. Staying in levels 2 and 3 would double that distance, unless there are hills involved.


The designers of this bike were thinking about commuters. If you live only five miles or less from your work, riding a bike to get there makes sense, especially if it requires only half of the pedaling effort. That’s why the Flow comes with a rear rack to attach your briefcase or whatever. It also comes with a front headlight in case you get caught out after dark on your way home. The bell is another feature we liked. It’s built right into the left assembly for the brake lever. There’s another little clever lever that gives you a “ching-ching.” You don’t realize how important a warning bell is until you’re coming up on other riders at speed. Many are not paying attention and will turn right into you as you’re trying to go by. A friendly bell sound is a polite way of saying, “Please give me room,” whereas a horn might be met with an annoyed look.

The handlebar shape is more pulled back than what you might find on some city bikes, but they’re comfortable at a cruising pace. The stem is adjustable up and down to find the right handlebar height for you. The ergo grips bring added comfort too.


When you’re pedaling along at a swift pace, the one thing you might notice is that the cable-operated disc brakes require more hand effort than the hydraulic disc brakes that come on the pricier bikes. Another thing we noticed while riding the Flow is the power delivery is slightly delayed on take-off. Let’s say you stop at an intersection and then you want to quickly go when the light turns green. For the first two strokes of your legs, you’re riding a regular bike that weighs 46 pounds, and then the electric motor kicks in. This is a safety feature to keep beginners from getting into trouble. For e-bikes that kick in sooner, you have to be careful when moving the pedals while starting out in a tight spot. For the Flow, we found ourselves downshifting extra gears when coming to a stop in preparation for a quicker take-off from our own legs.

A nice feature of the Flow is that it has a torque sensor for the electric motor instead of a cadence sensor. What this means is that you get more juice from the motor if you’re pushing harder on the pedals. That really helps when you’re trying to pedal up a steep hill.


The Espin Flow comes with its own battery charger that plugs into a normal wall socket. With a completely drained battery, it takes around four hours to get it back up to full charge. For theft prevention, the battery is locked to the bike, which requires a key to remove it. The battery doesn’t need to be removed to charge it, but you do have to unlock it and pull it out an inch or so to get to the hole the charger cord plugs into. With many e-bikes, you can plug in the charger without the need for a key, and that is what our test crew prefers. The reason why is because we sometimes lose keys. For our fleet of test bikes, we’ve learned to zip-tie the key to the end of the charger cord that plugs into the battery.

Espin offers two model bikes, with one being the Flow we tested here and the other being the Sport. The Sport is not a step-through design but has the normal top tube. It also has a straighter-style handlebar instead of the pull-back style. The Sport is listed as having a 20-inch frame versus the Flow’s 17-inch frame. Everything else on the two bikes is the same.

On their website, the Flow is shown with fenders, but they were not included with the test bike we received. When ordering the bike, you should specify if you want fenders or not. As of now, the Espin bikes are only available as a consumer-direct model for $1,588


The Flow has an appealing look, stealthy electrics and is well built for the price. The 350-watt motor provides a decent amount of power, and coupled with the 11.6-amp-hour battery, it provides great range for those who need a little boost and a decent range for those who need (or want) a little help.


MSRP: $1,588

Motor: Geared hub, 350 watts

Battery: Panasonic lithium-ion, 36V, 11.6 Ah, 418 Wh

Charge time: 4 hours

Top speed: 20 mph

Range: 25 to 50 miles depending on terrain and assist level

Drive: Shimano Acera Rapid Fire 8-speed

Brakes: Tektro Novela mechanical disc with integrated motor cut0off, 160mm rotors

Tires: Kenda Kwest 26×1.95

Fork: SR Suntour Nex suspension

Control display: Espin LCD backlit, speed, battery, odometer, time, assist level

Frame: Aluminum 17”

Weight: 46 pounds

Colors: Matte black or matte white


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