A folding bike for commuting has to survive two conflicting jobs. You need a ride that doesn't beat you up on potholes, and a package small enough for a crowded train, a studio closet, or the space under a desk. Brompton, Dahon, and Tern still own most of that market. They don't make the same compromises.
So which one should you actually buy?
It depends on whether you'll carry the folded bike up stairs, how long you pedal between stops, and what your transit operator will allow on board. Folded volume, wheel size, and carry weight decide that faster than brand loyalty.
Folded size is the first filter
City riders who skip a cover usually want a folded volume under about 200 litres, because that is the range where you can hold the bike uncovered without dominating a vestibule. Brompton's classic C Line fold is 585 x 565 x 270 mm, or about 89 litres. That is the figure most people mean when they say a folder "disappears."
Dahon 20-inch models sit in a different band. Folding Bike Guy's Dahon comparison puts the Vybe D7 around 145 litres and the Mariner D8 II around 195 litres, using rectangular volume from listed dimensions. Those numbers are bigger than a Brompton. They still fit a closet. They are not "needs a cargo bag every time" bikes.
Tern's older published folds were bulkier. A 2017 Cyclingabout roundup listed the Joe Tour at 870 x 950 x 460 mm (380 litres) and the Eclipse at 810 x 900 x 380 mm (277 litres). Those packages usually wanted a cover. Tern's current BYB is a different idea: it packs about 30% smaller than a typical folder, stands on its own, and can roll beside you through a station.
Thing is, volume is not the same as "allowed on the bus." Rules change by city and by time of day. Some systems treat a small folded bike like luggage. Others restrict bikes in peak hours no matter how tiny they are. Check the operator you actually use before you buy around a 30 x 30 inch rumor.
Fold speed still matters on a platform with gloves on. Brompton's three-stage fold is often under 20 seconds; Folding Bike Guy says the C Line 6-speed can fold in 15 seconds or less. Dahon advertises a three-step Dahon Folding System on the Mariner. Tern's Vektron, an e-bike, folds in about ten seconds according to Clever Cycles.
Small wheels save space. They also change the ride.
Sixteen-inch wheels, the Brompton C Line standard, make the smallest parcel. They also drop into potholes more readily. On a 15-minute hop to the station that is rarely a crisis. On a 50-minute road with broken asphalt, reviewers have called that ride tedious for years. Cyclingabout said as much in 2017. Cyclist still praises the platform's durability, which is a different claim.
Twenty-inch wheels are the commuting middle. Dahon's Mariner D8 and Vybe D7 use them. So do many Terns. You give up some folded compactness. You gain a more stable, less fidgety feel over typical city surfaces.
Brompton's G Line tries to split that gap: same three-stage origami, 20-inch wheels, wider tires. Velorution's G Line vs C Line notes put the G Line fold at 690 x 730 x 402 mm, more than twice the classic volume by Brompton's figures. At 14.8 kg, it's a bike you fold to store or to put in a car, not one you happily carry up three flights every morning. The electric G Line makes that even clearer.
Larger 26- and 27.5-inch folding bikes can feel close to a regular hybrid on longer rides. They fold into something you bag. If your "commute" is really a mixed train-plus-10-mile ride, that trade can be worth it. If you live in a walk-up and ride the subway, it usually isn't.
Cyclingabout and a Brompton vs Dahon comparison both land on the same split: small wheels win in tight streets, and they wear people down when the ride stretches past an hour.
Brompton, Dahon, and Tern side by side
These brands overlap on paper and diverge in daily use. Brompton is the compact specialist with a long parts ecosystem. Dahon is often the value 20-inch folder. Tern leans toward a more full-sized ride and, on some models, a rolling folded package.
Published specs don't all use the same measuring method. Treat the table as a map, not a lab report.
| Model | Folded size / volume | Wheels | Fold time | Best used for |
|---|---|---|---|---|
| Brompton C Line | 585 x 565 x 270 mm (~89 L) | 16 in | ~15-20 s | Tightest everyday carry |
| Brompton G Line | 690 x 730 x 402 mm | 20 in | Same fold, bulkier parcel | Longer rides; car or closet storage |
| Dahon Vybe D7 | ~31.5 x 11.0 x 25.6 in (~145 L) | 20 in | Under 10 s in some listings | Lower-cost 20 in commute |
| Dahon Mariner D8 | ~32.7 x 13.8 x 26.4 in (~195 L) | 20 in | 3-step Dahon fold | 8-speed city kit |
| Dahon Mu SL | 660 x 820 x 320 mm (173 L, 2017 figure) | 20 in | Not recently retested here | Mid-volume 20 in |
| Dahon Link D8 | Compact; bars can sit outside the bundle | 20 in | Quick | Commute builds with tougher tires |
| Tern BYB | About 30% smaller than a typical folder | 20 in class | Stands and rolls | Stations and indoor rolling |
| Tern Vektron | Larger than a Brompton cube | 20 in e-bike | ~10 s | Hills with a mid-drive |
| Tern Eclipse | 810 x 900 x 380 mm (277 L, 2017) | 26 in | Not listed | Longer rides, usually bagged |
| Tern Joe Tour | 870 x 950 x 460 mm (380 L, 2017) | 27.5 in | Not listed | Full-size feel; cover needed |
| Very D9 | Compact in 2024 listings | Larger | ~10 s | Fast fold and wide gearing |
C Line dimensions match the classic fold cited against the G Line by Velorution. Dahon volumes come from Folding Bike Guy. Tern fold behavior is from Clever Cycles. Joe Tour, Eclipse, and Mu SL volumes are the 2017 Cyclingabout measurements, useful for scale even if those exact trims are no longer the ones on a showroom floor. Vybe fold-time claims also show up in a Bikersays Dahon roundup. Very D9's 10-second fold is from Folding Bike Guy's commuting guide.
Brompton C Line Urban weight is listed around 24.8 lb, Utility 26 lb, Explore 26.7 lb in Folding Bike Guy's Brompton lineup. Electric C Line models jump to about 32-34 lb. That's the difference between carrying the bike up stairs and talking yourself out of it.
Dahon's Vybe D7 shows up around 25.7 lb in that same retail roundup. The Mariner D8 uses a Shimano 8-speed with a 52T chainring and 11-32T cassette, an aluminum frame, and corrosion-resistant hardware aimed at wet city and coastal use. Dahon also says a large share of folding bikes use its hinge patents. That's company language, not an independent census.
Tern's pitch is ride quality and kit: longer wheelbases on 20-inch models, racks, and in the Vektron a Bosch mid-drive that still folds. Cyclist has described well-equipped 20-inch Terns as feeling closer to a full-size bike. You pay for that in folded bulk unless you pick the BYB.
Resale is a soft number. One folding-bike roundup claimed Brompton holds roughly 70-80% of MSRP after three years, Tern 50-60%, and Dahon 30-40%. That's one editorial estimate, not a market index. It does match what shops tend to say: Brompton parts and demand prop up used prices.
Gears, hills, and who actually fits
A 6-speed Brompton Explore trim is often described as covering about 33% to 100% of typical road-bike gearing, enough for real hills if you accept a slower cadence. The C Line 12-speed spreads about 402% according to Velorution, with more exposed moving parts. An Alfine hub, cited around a 307% range in older comparisons, keeps the mechanism enclosed. That helps in rain and grit.
Dahon Mariner's 8-speed Shimano setup is conventional and easy to service at any bike shop. That's not glamorous. It's useful when you don't live near a Brompton dealer. Wirecutter has also pointed to Dahon Link D8 builds with puncture-resistant tires, which matters more than gear count if your streets eat inner tubes.
Wirecutter has long used a rough rider window around 4 ft 8 in to 6 ft 3 in and a load cap near 220 lb for many folders. Confirm the exact limit on the frame you buy. Seatposts, hinges, and e-bike motors change that number.
to be honest, fit on a folder is weirder than on a diamond-frame bike because the cockpit and the fold share the same tubes, a too-short stem or a slammed saddle can make a 20-minute ride feel like an hour, and you won't know until you try the exact size with your bag on your back.
P and T Line Bromptons exist if carrying weight is the bottleneck. FoldnGo's line guide frames the C Line as the daily foundation and the P Line as the lighter, more refined carry. If the bike lives in a garage and never goes up stairs, save the money.
Match the bike to the route you already ride
Work through your actual commute, not a catalog page.
- Measure the tightest storage you have: closet depth, under-desk height, car trunk. If that space is under about 200 litres of bike, start with a classic Brompton fold or a compact Dahon like the K3 family, which Folding Bike Guy says packs into 49% of a Mariner D8 II.
- Time the ride, not the miles. Under 20 minutes of poor pavement, 16-inch wheels are usually fine. Thirty to 60 minutes, prefer 20-inch. Longer mixed-surface days push you toward G Line, Tern, or a larger-wheel folder you will bag.
- Count stairs and whether you'll carry or roll. If you carry daily, weight under about 27 lb matters. If you roll a BYB or stash in a car, G Line bulk is less of a problem.
- Read your transit operator's bike policy for peak hours, folded vs unfolded, and e-bikes. Do not assume a 30 x 30 inch rule applies everywhere. One U.S. rail example, summarized in a note on bringing e-bikes on the subway, allows bikes and scooters on Metrorail under 80 in long, 48 in high, and 22 in wide. Your city may be stricter at 8 a.m.
- Test the fold 10 times in the shop, with your commute bag on. A 10-second fold on a stand is not the same as a fold on a wet platform.
Bring a tape measure and the bag you actually wear. Ask about replacement hinges and whether local shops stock the tires. Sixteen-inch Brompton tires are easier in Brompton-heavy cities and annoying everywhere else. Fenders and a rack are the unsexy bits that make a rain commute possible; many Tern kits and Dahon city builds include them, while Brompton owners often add luggage blocks later.
Covers, bags, and when size stops mattering
Once you need a cover, the 89-litre advantage shrinks because the bag is now part of the package you haul. A larger Tern you roll or bag can be easier in a station than a coverless cube you still have to carry by the saddle.
Electric folders change the carry, not just the hills
Assistance is the honest fix for a hilly commute or a rider who arrives at work in a shirt. It also adds weight exactly where you don't want it when you lift the bike. Range, charge time, and motor placement vary by model and battery, so treat any mileage claim as a starting point, not a guarantee.
Brompton's electric C Line uses a front-hub motor and a removable battery. Run Bike Calc puts a typical electric C Line around 35 lb with a claimed 25-45 mile range. Folding Bike Guy lists Electric C Line Explore around 32 lb, with assist covering about 20 to 45 miles and a 15.5 mph cap in the writeups that describe those bikes. The battery clips off the front block so you can charge under a desk. Carrying that extra front weight up stairs is the part people underestimate.
Tern's Vektron is a Bosch mid-drive that still folds in about ten seconds. That's a different machine: more "real e-bike that happens to fold" than "folder with a motor." Heavier. Better on hills. Harder to treat as luggage.
Turns out the electric decision is mostly about stairs. If you never carry the bike, assist is easy to like. If you do, try the lift in the shop with the battery installed.
You carry it. You carry it up the stairs, then you carry it onto the train, then you carry it again at the office, and if any of those lifts is a problem, weight beats folded millimeters.
Transit and building rules for e-bikes are not the same as for analog folders. Some systems restrict batteries, wattage, or peak-hour e-bikes even when a folded acoustic bike is fine. Ask before you assume the fold gets you a free pass.
FAQ
Which folding bike is smallest for public transit?
The classic Brompton C Line fold at 585 x 565 x 270 mm (about 89 L) is still the tightest widely available package among these three brands. Wirecutter and older Cyclingabout measurements agree on that compactness. G Line is a Brompton that does not win this contest.
Are 16-inch or 20-inch wheels better for commuting?
Sixteen-inch wins on folded size. Twenty-inch wins on stability for typical 30- to 60-minute city rides. If most of your trip is on a train, buy the small fold. If most of it is pedaling, buy the bigger wheels.
Can these bikes handle riders over 220 lb or rides longer than an hour?
Many folders are specified near 220 lb and a 4 ft 8 in to 6 ft 3 in height band, per Wirecutter. Check the exact model. For longer rides, 20-inch and up (Tern, Brompton G Line, Dahon 20-inch) fatigue people less than 16-inch C Lines, which is the old complaint in Cyclingabout's touring notes.
How fast do they actually fold?
Shop claims cluster around 10-20 seconds for Brompton, Dahon, Very D9, and Tern Vektron once you know the sequence. Slow folders exist in the wider market. Practice matters more than the brochure.
Brompton or Dahon for a tighter fold and a better ride?
Brompton folds smaller than a Mariner D8 by a clear margin. Dahon 20-inch models often ride more planted for the money. Brompton's long-term parts and used values are the other half of that price. Ride length should decide it.
Take a tape measure to the space the bike has to live in, then fold the shortlist in person with your backpack on. Spec sheets won't tell you if the hinge bites your shin.