What makes the best folding bike? Whether it’s a cycling vacation, a weekend adventure or daily commute, a folding bikes pleasure comes down to some frictionless mathematics. It’s all about how things measure up… literally! First, a folding bike must measure up small when folded. Second, it must measure really big when unfolded (we’ll explain why). And third, it must be engineered so that it folds and unfolds simply. Sound obvious? Well, very few brands measure up to all three. Grab your measuring tape and let’s dig in!

Big On Ride Quality

If a folding bike is going to be ridden in a pothole-strewn city, then it has to be big on ride quality. But, good ride quality means it has to unfold big. What does big mean? A bikes bigness is its “wheelbase.” If you’re buying a folding bike and the word “wheelbase” doesn’t come up, then something is very wrong. The wheelbase on a bike is the measurement from the front axle to the rear axle, and it represents the overall stability or footprint of the bike.

Wheelbase is especially important when a bike has smaller wheels. Small wheels, incidentally, are the best for the city. With a bigger wheel, it takes more time to accelerate to top speed, and when you reach top speed, you hit another stop light (in the city, at least). But, a small wheel is pure acceleration, so you leap from one stoplight to the next. Small wheels also manoeuvre much faster. That’s why a folding bike is best for the city.

But, all the natural assets of a small wheel disappear on a short wheelbase. A short wheelbase means the bike starts to feel quite squirrelly and scary. If you were to design the best city bike, it would have small wheels on a long wheelbase. And, it would fold. Why? Because cycling in the city generally takes you indoors, not outdoors. But, it’s this folding that introduces a new problem to solve.

Small on Portability

Ride quality is never something that should be sacrificed for portability, ever. Boiled down to its essence, ride quality means safety. But, if you’re designing a folding bike, this generates a fairly large mathematical paradox. How can I design a bike that measures big unfolded yet measures small folded? Of course, the real question is: what is the point of folding up a bike if its just as awkward folded as it is unfolded? Like really… what’s the point?

The use-case here has to do with indoors versus outdoors. When the bike is unfolded it is generally outside. And, when it is folded it is generally inside. It could be parked beside your desk, in a gallery coatcheck or in your closet at home, safe from thieves. Or, it’s moving around inside, like when you’re doing a grocery trip. Finally, it could be inside but the inside itself is moving – think of it being inside of a train, plane or automobile. If your folding bike is like carrying a big, heavy suitcase wherever you go indoors, then it’s a failure of design.

Quick On The Physics

Thus far we have seen how a short wheelbase with an unsafe ride is a failure of design. Likewise, a bike that folds so big and heavy is also a failure of design. But, even if you were to accomplish a stable ride and small fold, the next issue is that the folding and unfolding has to be easy. That’s right: another engineering puzzle! Overly complex folding mechanisms with fiddly transitions hinder usability, making the folding process something you’d rather forget about altogether. And that prompts the question: why buy a folding bike you’ll never fold?

Foldability also comes down to math. It is all about engineering without over-engineering. Ultimately, it’s about creating incredibly tight tolerances that guarantee a snug and small fold. That means engineering parts that are meant for folding bikes, and quality control that ensures all straight lines are in fact straight. And, that takes a company-wide commitment to engineering standards that most companies don’t have the experience, knowledge or chutzpah to engineer. If you want to build the best folding bike, you better mean it!

In Comparison

So, building the best folding bike is quite difficult. It has to resolve a measurement paradox by folding small yet unfolding big. And, it has to resolve this paradox without frustration. And, the only company who measures up is Brompton.

Let’s begin with wheelbase. For sake of context lets not just compare a Brompton to another brand of folding bike. In fact, let’s compare Brompton to a regular bike. Let’s take a popular hybrid bike like the Trek FX. This has a wheelbase of 1045mm. The 16″ wheeled Brompton also has a wheelbase of 1045mm. That means that despite it’s small wheels, a Brompton is the same size as a regular bike, only the smaller wheels make it faster in city traffic.

Now, let’s compare the G-Line bike. If a regular bike has a wheelbase of 1045mm, the G-Line has a wheelbase of 1165mm. That’s a whole lot of bike planted on the ground! Well, the G-Line takes that stability and adds some speed and cornering with its smaller 20″ wheels. That means it feels safe when speed picks up. For proof, we took a G-Line to the UCI certified Paris-Ancaster race and it placed in the top 10%. It just takes one test-ride to understand that the G-Line can do anything.

But, now let’s compare the 16″ and 20″ Brompton bikes to the popular 20″ wheeled Tern bicycles. A Tern has a 1025mm wheelbase. That means the ride is squirrelly. On top of this short wheelbase and poor ride quality, a Tern folds up to an absolute monster – 8 cubic feet. The Tern is also notoriously fiddly to fold. A fiddly bike that unfolds small and folds big really makes no sense, unless you just want something cheap to ride once or twice a year. Then, fair enough.

Strange Company

How did Brompton solve the engineering paradox of an easy to fold bike that unfolds to a regular size bike while compressing to something the size of a backpack? The answer is engineering. And character. Lot’s of character. It takes a stubborn obsession to produce a bike like Brompton, but it also takes top-level engineering. And, a compulsion to keep improving. Brompton has all of this in spades. Unlike Tern bikes, which were designed in Los Angeles to fit in the trunk of a car, a Brompton was originally designed to fold small for the teensy-tiny London Tube while unfolding big to handle all the English potholes.

England once had medieval guilds, was home to the vertical integration of the industrial revolution, and has adopted just-in-time inventory practices. If a Brompton is eccentric it’s because it marries all three. We’ve been working with Brompton since 2006, and they might be one of the strangest companies to succeed in the world today. That helps explain why there is such a tribe around Brompton.

A Fun Conclusion

All this math, geometry, and obsessive engineering doesn’t just exist for its own sake – it’s in service of something radically practical. A Brompton gives you the stability of a full-size bike, the portability of a carry-on, and the speed and agility to outpace traffic. It folds in seconds, fits under a desk, and dodges every cost and hassle of car ownership. No gas, no parking, no theft, no problem. It’s the best folding bike ever – and, it’s the best city bike ever.

But the best part? It’s really fun. It’s fun on a commute and it’s fun if you’re planning to ride around Europe. A Brompton is fun if you’re living the van-life, own a sailboat, or just want to take the train for a weekend in Montreal. It’s all city bike, but there’s a bonus level too: whether work or vacation, it’s the best travel companion you’ll ever have.