Brompton G Line Urban review

The Brompton G Line is the legendary folding bike brand‘s radical new model. It was launched in 2024, with larger 20-inch wheels and a redesigned, larger frame to fit around them, as well as disc brakes and off-road tyres that the brand says makes it a viable option for more than just the commute, and even gravel riding.

It’s a big departure for Brompton, which has made the same 16in wheel bike – albeit with spec and material variations – since the company began in the 1970s, but the theory is the same, just sized up and with some important performance tweaks.

I was given the opportunity to test the road-going build with slick tyres and, despite the obvious folded size and weight negatives in comparison with the other Bromptons, the ride quality is excellent, it’s more capable and it should still be compact enough for many people.

The Brompton G Line starts from £2,399 / €2,849 for the non-electric bike without the Roller Frame; with the Roller Frame prices start from £2,499 / €2,969 / $3,300.

Brompton G Line development

After half a century building bikes with 16-inch wheels, making the G Line was a bold step, but the view was that it had the potential to reach a different customer base than the existing loyal – and international – Brompton owners. Whereas the smaller bike is popular in big cities, where space is at a premium – especially in Asia – the G Line’s more versatile performance claims theoretically makes it more fitting for city-dwellers just a train ride or car drive away from the great outdoors.

The journey began with the simple proposition: how could they get 20in wheels on a Brompton? Tom Kerr, G Line design lead, explained the full development and prototyping process to me in this article, but the tl;dr version: step one was getting big wheels on and it not being too crazy; step two was a fleet of prototypes with different geometries to find the right balance; step three was finding the right componentry for the job and refining the folding process; step four was proving they could build it in the factory.

The final product is certainly different, however it still looks like a Brompton and folds like a Brompton.

There are suggestions from Brompton that this isn’t the final product, however, and that, much like the smaller bike, it’s a platform to do different things with. Brompton was tight lipped about what that meant, but I would expect a heavier lean into the adventure side and a lightweight build á la the titanium T Line, at the very least.

Brompton G Line build

The bigger frame opened up new build possibilities for Brompton. While the smaller bikes had a wealth of proprietary technology involved, including in the drivetrain, the size of the G Line meant Brompton has been able to use Shimano Alfine hub gears, saving space in the fold that a cassette (especially with eight gears) would take up, keeping required maintenance down, and bringing reliable performance that didn't need extra development or experimentation in the design process.

The shifting is done through Microshift trigger shifters, which are intuitive to use, and there's a dial so you know what gear you're in.

Another big departure from the rest of Brompton's range is the addition of disc brakes, which will not only help those who do plan to take the G Line off-road, but also inner-city commuters considering the extra stopping control disc brakes bring in all weather conditions. For this, Brompton signed up Tektro to supply the parts, with 140mm rotors.

Then there's the tyres, probably the most understated development of the bike judging from the coverage it received at launch. Even ignoring the gravel-ready build with the Schwalbe G One tyres, the urban G Line here is also fitted with 50mm tyres, up from the 35mm standard for smaller Bromptons. In general, this allows riders to run lower tyre pressures, adding comfort and grip. And if you are going for the gravel setup, the Schwalbe tyres come tubeless-ready, which is a big plus from me.

Elsewhere the G Line's size means Brompton has also been able to add further comfort-focussed features, including wide handlebars with ergonomic grips and wide pedals.

Brompton G Line geometry

The new-for-Brompton size means the team has had to figure out a new bike's geometry for the first time in decades. It also means that while most Bromptons come in one size only, the G Line has three sizes.

However there aren't many changes between the small, medium and large options, only the stem and seatpost change, and the seatpost is more adjustable the bigger the size.

My G Line was a size large, so came with the telescopic seatpost, which has two quick release adjustment points, which is necessary to be able to hide the full length inside the seat tube so the fold isn't compromised.

I'm about 188cm tall and didn't actually require the full telescopic extension. as I got the length I needed from the end of the first section.

Riding (and using) the Brompton G Line

It might look like and fold like a 16in Brompton, but it rides nearer to a full size hybrid bike. The increased stack height from the raised bars means you sit much more upright than a smaller Brompton, which I personally prefer for the riding I was doing on it.

Unlike most reviewers, I was riding the full Urban setup of the G Line as opposed to the adventure build with the gravel tyres, so I found it very easy to make a direct comparison with the 16in-wheeled Brompton bikes.

From a pure riding point of view, I found the G Line far superior. It's more comfortable and more capable, even just riding on tarmac. The big tyres made the bike more comfortable, the disc brakes offered more confident and repeatable stopping power, and the gearing is ideal for the riding I do in the city (hills included).

One thing that stuck with me from talking to Tom Kerr, the G Line design lead, was that he mentioned the G Line has proven that certain design and build features are possible on a Brompton and may therefore be implemented on the smaller bikes.

The other side to the Brompton is that its function when not being ridden is just as important. And that's where you're always going to struggle slightly when comparing a bigger bike to a smaller bike. Unsurprisingly the G Line is heavier and less compact when folded.

I weighed this size large with the roller frame and lights at 14.9kg. That obviously makes it less favourable than smaller Bromptons to carry up or down stairs to the train or into an apartment, but I don't think it's a dealbreaker.

Its folded size is 72cm (depth) x 67cm (height) x 41cm (width). If you have that space then, again, it's not a dealbreaker, but a large number of Brompton's existing customer base will have bought the smaller bike because they want to save extra centimetre possible, and it would definitely make it harder to travel on a rush hour train. I found the awkwardness of carrying its larger dimensions more of an issue than the weight.

However, that's why the company expects this is for a different audience. It is still easy to take on a train when it's not overly crowded, and it's very easy to pack into a car.

Most importantly, it's still incredibly easy to fold, and on top of that, the roller frame – which has been refined for the G Line – works very well (just don't let go of it on an incline).

Brompton G Line review verdict

In isolation, the Brompton G Line is an excellent bike. It folds brilliantly, it rides brilliantly, and it's obviously more compact than a full-size bike.

The only question is its audience. I expect there to be some take up with the Brompton superfans across the world, but whether it can successfully capture the new target consumer will, I think, be make or break given the news of the company's drastic drop in profits. And it faces much more competition among those people than it does with the 16-inch bikes.

The extra size and weight will certainly put some customers off. That said, if I were in the market for a folding bike and didn't need to go as small as the other Bromptons, I would not hesitate to get a G Line. I would, however, get the build with gravel tyres, because that would only add to this bike's capability.

• Buy the Brompton G Line Urban now from Edinburgh Bike Coop (£2,499)