Review: Dahon Formula S18 Folding Bike

Putting 5 collapsible commuter bikes to the test
Chris Lesser

Dahon Formula S18; $1,399 

Who it’s for: Roadies with small apartments who like long, fast rides.

Vital Stats:
Folded Size: 11.3 x 25.7 x 31.2 inches(5.2 cubic feet)
Wheel Size: 20”
Weight: 24.5 lbs
Hits: best brakes in the group, well-appointed drivetrain spec, geared for speed, lightest bike we tested
Misses: frame flexes more than we’d like, cumbersome to roll when folded, wobbly steering stem, $1,400 will get you a decent full-size road bike
Ride Foldability Rank: Tied for 2nd Place (with the Tern Eclipse P9)
Extras: Water bottle and pannier mounts, flip-down pedals, reflective Schwalbe Kojak tires, ergonomic grips
Buy It:

Dahon has been one of the leading names in folding bikes for decades, and that experience is evident in all of the little details that make up the Formula S18. Note the forged I-Beam seat post clamp, anodized height markings on the post itself, brass bushings for smooth action on its many quick-release levers and nicely-finished frame welds and paint job.

The “S” stands for Sport, and the “18” refers to its 18-speed drivetrain, which consists of an 11-25t 9-speed cassette and a massive 56/46 double-ring crank. For reference, a 56-tooth ring is as big as a Tour de France-level rider would ever choose, and many opt for a smaller gear. But don't let that scare you—combined with the BMX-sized wheels, the gearing nets out about what a normal road bike feels like. [slideshow:517]

Unlike the other folding bikes in this test, the Dahon has an extra telescoping arm built into its stem, allowing a range of different sized riders to achieve a proper fit. It’s also the only bike of the bunch besides the Montague to use full-sized 175mm crank arms, and is the only model to use outboard bottom bracket bearings.

In essence, this is a performance road bike that just happens to have pint-sized 20-inch wheels, which are ably controlled by the best brakes in the test group—Avid BB5s with 6-inch rotors. The Dahon’s MicroShift trigger shifters performed far better than the MicroShift twist-shifters on the Pacific, and this bike’s Shimano Tiagra rear derailleur provided smooth, reliable shifting.

The bike folds and unfolds relatively intuitively, with minimal fuss, but how does it ride? It’s strangely speedy, and its full-sized fit dimensions allow even taller riders to really put the hammer down. Compared to the 22-inch-wheel Pacific Reach IF, the frame certainly flexed a little more, but not necessarily in a good way. Giving the bike the old wiggle test, I managed to get the handlebars to squeak themselves a few degrees out of alignment. Not a big deal, as they straightened out easily enough with the simple readjustment of a quick-release. The target rider for this bike is going to be looking for less of a BMX or mountain bike type of ride, and more of a fitness-based, road bike experience.

Second Opinion: It’s true that I ride my bike at least six days a week, but Chris knows a lot more about bikes than I do (thank God he’s the Bike Editor). Many of the finer details he lists above were lost on me while I was out, spinning this model around the city. What I can tell you with certainty is that the disc brakes on this bike are sticky as hell, and it’s a big plus to have adjustable handlebars, especially for taller people. Like Chris says, there’s quite a bit of flex in the frame, which is a real pain when you’re dropping the hammer like Cavendish, trying to beat a road bike off the line at a red light. As commuters go, though, it’s a solid, high-performance entry. —Peter Koch

More Info:

See the other collapsible commuter bikes we tested from Brompton, Montague, Tern and Pacific Cycles.