Dahon Formula S18 Review

Dahon Formula E18 Electric Bike Review 1
Dahon Formula E18
Dahon Formula E18 350 Watt Motor
Dahon Formula E18 Battery
Dahon Formula E18 Bionx
Dahon Formula E18 Disc Brakes
Dahon Formula E18 Electric Bike Review 1
Dahon Formula E18
Dahon Formula E18 350 Watt Motor
Dahon Formula E18 Battery
Dahon Formula E18 Bionx
Dahon Formula E18 Disc Brakes


  • Sturdy, light weight and well balanced folding electric bike conversion from leading folding bike company Dahon
  • Uses the BionX gearless motor and battery system, offers throttle, pedal assist and four regenerative modes
  • Full length crank arms, extra long seat post and outboard bearing bottom bracket create smooth comfortable ride

Video Review





Formula S18 (Originally Formula E18)


$3,000 USD

Body Position:


Suggested Use:

Urban, Travel

Electric Bike Class:

Throttle on Demand (Class 2)
Learn more about Ebike classes


5 Year Frame, 2 Year Motor and Battery, 1 Year Mechanical Parts


United States

Model Year:


Bicycle Details

Total Weight:

39.5 lbs (17.91 kg)

Battery Weight:

9 lbs (4.08 kg)

Motor Weight:

6 lbs (2.72 kg)

Frame Material:

7005 Double-Butted Aluminum Alloy

Geometry Measurements:

Folded Size: (29 cm x 66 cm x 80 cm)

Frame Types:

Step-Thru, Folding

Frame Colors:

White with Black Accents

Frame Fork Details:

Rigid Aluminum Alloy

Attachment Points:

Rear Rack Bosses, Fender Bosses

Gearing Details:

18 Speed 2x9 Shimano Tiagra

Shifter Details:

Microshift Thumb Tap Trigers on Left and Right Bar


Cold-Forged 6061-T6 Aluminum


VP 529 Aluminum Alloy Platform


No Rise

Brake Details:

SRAM DB BB5 Mechanical Disc


Rubber, Ergonomic


Dahon Comfort

Seat Post:

Kore, Extra Long

Seat Post Length:

580 mm

Seat Post Diameter:

34 mm


WTB Double Walled Aluminum Alloy

Tire Brand:

Schwalbe Kojak

Wheel Sizes:

20 in (50.8cm)


Magnetic Clasp for Fixed Folded Position


Shimano Outboard Bearing Bottom Bracket (Lighter and More Durable), Removable Battery Pack, Quick Release Front Wheel

Electronic Details

Motor Brand:


Motor Type:

Rear-Mounted Gearless Direct Drive Hub
Learn more about Ebike motors

Motor Nominal Output:

350 watts

Motor Peak Output:

700 watts

Motor Torque:

32 Newton meters (10 Nm Nominal)

Battery Brand:


Battery Voltage:

48 volts

Battery Amp Hours:

6.6 ah

Battery Watt Hours:

316.8 wh

Battery Chemistry:


Charge Time:

3.5 hours

Estimated Min Range:

30 miles (48 km)

Estimated Max Range:

45 miles (72 km)

Display Type:

Removable Backlit Monochrome LCD


Speed, Odometer, Battery Level, Assist Level (1-4), Regen Level (1-4)

Display Accessories:

Independent Button Pad on Left Bar

Drive Mode:

Torque Sensing Pedal Assist, Trigger Throttle

Top Speed:

20 mph (32 kph)

Written Review

Dahon is one of the earliest, most innovative and well known companies in the folding bicycle space. They know how to make quality cycles and just recently entered into the electric bicycle space (sort of). In 2013 they teamed up with IZIP to create the E3 Compact but that bike used a rear rack battery and only offered one speed. The Formula S18 delivers 18 speeds and thanks to a BionX conversion kit it features a mid-mount battery for improved balance. Originally this bike was called the E18 (E for electric) which is why I refer to it that way in the video review. It’s one of the lightest weight, highest quality folding ebikes I’ve tried and really benefits from the versitility of BionX drive systems. The best way to test ride and purchase this ebike is to go through NYCeWheels, a long running bicycle shop focused on folding bikes based out of New York City.

The motor driving Dahon’s Formula S18 electric conversion is a 350 watt gearless design built by BionX. It’s based on the SL-350 kit (which costs nearly $2,000 on it’s own). This motor is great because it offers regenerative riding and braking functionality and coasts silently (being gearless). During my ride tests it also offered plenty of torque when starting from rest and powering up hills. The SL Series motors from BionX are 2.5 pounds lighter than their older PL series and I like the wavy aesthetic of the hub casing which is made from metal to provide strength and protection.

The battery pack powering the S18 offers 48 volts of power with 6.6 amp hours of capacity. This is part of what makes the bike so powerful, 48 volts is what some of the larger full sized ebikes offer! If you are looking for a folding style ebike that can actually power up some hills and won’t struggle with extra weight, this is the proper size to look for. Higher voltage also flows more efficiently so this bike gets excellent range. I was told by the Dahon and BionX reps that the battery chemistry used in this pack is designed to store longer without discharge. This makes a lot of sense considering folding ebikes are often left on a boat, RV or other holding area between trips. Even so, make sure you top off the battery every few months if it hasn’t been used to help prolong its life. Together the motor and battery pack used for this bike weigh ~14.6 pounds and the frame by itself weighs ~24.5 pounds (for a combined total of ~39.1 lbs).

Motors and batteries are only as good as their controllers and control systems. Thankfully, BionX offers one of the most intuitive LCD computer displays I know of (with their second generation G2 offering) and it’s featured on this bike. The up and down keys let you navigate four levels of regen mode (perfect for coasting down hills and saving your brakes) and four levels of pedal assist mode slow you down or act as an exercise mode while adding juice back into the battery. You can also ride in “neutral mode” to pedal like a regular bicycle (which the S18 does quite well thanks to its light overall weight) and use the trigger throttle on demand. Note that the trigger throttle only works once the bike senses at least 2 miles per hour of movement. This is a safety feature of all BionX systems. I love that the display and battery pack are removable for safe storage or to make the bike even lighter when riding.

During my ride test I mostly relied on the trigger throttle to test the torque on the bike from standstill but for maximum range, pedal assist is best. This bike is said to reach up to 45 miles on a single charge which is quite good. I don’t know too many people who would actually want to ride that far on a folding electric bike however because they tend to be a little less forgiving due to the smaller wheel size and lack of suspension. Some of the other folding ebikes I’ve tested use shorter crank arms, shorter seat posts and soft pedals that don’t feel smooth, comfortable or responsive. Thankfully, that is not the case with this bike and that’s one of its biggest benefits. This bike rides great, almost as well as a full sized city bike, and is still able to fold down to be relatively compact. The pedals are aluminum so they stay stiffer when riding. The seat post is extra long and the crank arms are also full sized. The bottom bracket pedals very smooth because it uses an outboard bearing system which also makes it lighter.

This is one of my favorite folding electric bikes. It costs a bit more but actually rides like a full sized ebike and uses some of the best systems available. The weight of the motor and battery pack are balanced and kept low to the ground which makes it stable to ride and carry when folded. It coasts well and even rides well out of pedal assist mode because the hardware was kept full sized and there are lots of gears to choose from. The only downside to a bike like this is the lack of shocks. The smaller 20″ wheels and narrow tires don’t absorb as much vibration but the bike is still relatively comfortable, akin to a city or road bike. This would be a great choice for trips, to keep in an RV or boat or even as a commuter for work as it is comfortable, durable and could easily be carried on to a train, subway or bus.


  • Light weight, just ~40 pounds but still offers a large motor and battery pack
  • 350 watt gearless rear mounted hub motor is powerful and offers regen modes plus regenerative braking
  • Battery pack is designed to store longer without losing charge, great for part time use with a boat or RV
  • 48 volt battery is powerful, efficient and ideal for climbing hills, transporting larger riders and going far
  • Beautiful design with mid-mounted battery pack for improved balance and handling ability
  • Full sized crank arms and metal pedals are responsive and comfortable
  • Extra long seat post works well for larger riders, maximizes pedal strides
  • Offers both throttle mode and pedal assist mode for increased range or climbing and variety in riding (if you’re carrying groceries or something it’s convenient to just use the throttle)
  • Battery can be charged on or off the bike, mechanical disc brakes offer great stopping power


  • No holes for mounting a water bottle cage and the battery takes up this spot
  • A bit less forgiving than some folding ebikes (narrow tires, no shocks no seat post shock)
  • Bike has to be moving 2 miles per hour or more for throttle mode to work


Comments (14) YouTube Comments

Ken Sanders
11 years ago

Yup a good mix of bike and electric drive Bion x Dealer Ken Sanders

Lorraine Jacobs
10 years ago

Thank you so much for this wonderful review! Knowing all those features with Dahon seems very interesting. However, I am kind of concerned with the sit post with no shock and for its entire frame for not having shocks. I believe it is best to have it most especially when you can drive this to a little rocky road. But, all-in-all this entire kind of electric bike is really wonderful.

Bob McPhie
10 years ago

In Canada, government regulations prohibit the use of a throttle from a dead stop on an electric assist bicycle, otherwise it would be defined as a limited speed motorcycle. The distinction is made because their are to fees for operating an electric assist bikes, while there are licencing requirements for limited speed motorcycles. As BionX is a Canadian company, it’s only natural there system would conform to Canadian Laws. Besides, all my customers love the fact that it’s NOT a throttle based system. You see, they actually enjoy pedaling.

Court Rye
10 years ago

Very informative comment Bob! Thank you so much for explaining how things work in Canada and connecting that to the BionX system and their throttle design. I had always wondered why some ebikes require pedaling ~2mph before they let you use the throttle, your comment cleared it up!

Richard Edge
10 years ago

You probably won’t see this model in Europe, but one with a different version of Bionx system. Most parts of Europe are limited to 25 kph and 250 watts. Like Canada they also require that a throttle cannot activate from a dead stop to be classified as a bicycle. The e-assist engagement requiring a speed of 2 mph really shouldn’t be listed as a con as it is a legal requirement in many parts of the world. I rarely use the throttle if at all on my Bionx system since the torque sensing axle (unique to Bionx) which allows the motor to provide e-assist in proportion to the cyclists effort is all that is required with the correct assist setting to give you all the assistance you need.

Court Rye
10 years ago

Great feedback Richard! I appreciate the insight into how ebikes are setup around the world and agree that the 2mph isn’t exactly a con. Sometimes I just include extra points here to clarify how the system works that are more neutral.

Raymond Dimock
10 years ago

Only major con might be whether constant jiggling might cause excessive wear and tear on two bolts holding the Battery to folding frame, Love the BB7 Disc brakes, saving the 20″ rims from excessive heat buildup and normal wear and tear from regular rubber Caliper rim brakes. Since the rims and spokes are harder to source outside major cities. Disc Brakes are a major plus. Front rim has to fit 70 mm fork, so only Dahon parts for rebuild. Great effort on Dahon and Bionx for sure.

9 years ago

Actually Raymond Dimock the Dahon Formula s18 comes stock with Avid Sram DB BB5, disc brakes.

9 years ago

At 3k, do you think this is still a solid bike as of October 2015? Thanks for the website Court. Good luck

Court Rye
9 years ago

Hi Ricardo, this is definitely one of the higher quality folding ebikes I’ve tested… one of the only I know of with the BionX system. The $3k price tag definitely feels high but with assist, regen, throttle and the quality name-brand frame it makes sense. I’ve reviewed a bunch of other folding ebikes here if you’re exploring alternatives. The Gocycle G2 is very cool and also in that higher price range, I think I prefer the quietness of the BionX motor on the Dahon here but the purpose built design on the Gocycle is unmatched on almost any ebike folding or otherwise.

9 years ago

Court, would you say that a 24 inch, such as the Tern Node D8 Bionx, rides noticeably smoother than this bike? I don’t really need the compactness of a 20 inch.

Court Rye
9 years ago

Hi Ron, yeah the larger wheel feels more stable and smooth. You’ll get slightly better rolling momentum but mostly you just won’t have the same wobble feeling or unstable turns that can sometimes happen with 20″ folders. The Dahon Formula S18 is an awesome bike and very stable so no hate on this model but if you don’t need it to be that small then the Tern Node D8 is awesome, do you even need a folding bike at all? You can save weight and add strength with a non-folder :) anyway, the BionX drive system is great on both but I like the fenders and rack on the Tern.

Mark Sunbear
5 years ago

Hi. Does anyone know the replacement cost (US or CAD?) of the battery? Is the bike available in Canada?

5 years ago

Hi Mark! I live in Canada now and can pretty much confirm that the bike is no longer being sold as new, but that Virginia Block at Amego EV in Toronto Canada may have batteries and other replacement hardware for sale! I hope this helps, here’s her official website.


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