The Brompton modding community is in overdrive right now, racing to create the lightest Brompton G Line builds imaginable. They’ve already managed to shave the weight down from 14.84 kg to just 8.50 kg!
But even that pales in comparison to a recently unveiled CarbonDry Brompton, which weighs an astonishing 3.9 kg, making it the lightest folding bike in the world.
It’s important to remember that the Brompton G Line was never designed with speed or weight savings in mind. With its stiff frame, wide tyres, internal gear hub, and rugged components throughout, this folding bike is all about versatility, practicality and everyday utility.
In fact, the Brompton G Line frame and fork alone tip the scales at a rather weighty 4.2 kilograms – roughly three times the weight of a lightweight gravel bike frameset, or about the same as a Surly Disc Trucker steel touring bike frameset.
That hasn’t stopped enthusiasts from chasing performance gains, especially given the G Line’s advantages over the other Brompton models: larger 20″ wheels, a stiffer and longer frame, and the addition of disc brakes.
In this article, I’ll take you through the world’s lightest Brompton G Line build (so far!), showing you exactly how every gram was shed, one component at a time.
Note: This article was originally written in July 2025, but has been updated in March 2026.
The Lightest Brompton G Line Build Yet
To reduce the G Line’s weight to just 8.5 kg, Harvey Hung of the Brompton tuning brand HH Innovation took a no-compromise approach. In fact, every part has been modded, and it’s only the front frame triangle that remains.
It’s also worth considering that Harvey weighs just 53 kg himself, meaning any weight reduction on the bike will feel significantly more impactful (about 1.5 to 2 times more), compared to someone weighing 80 to 100 kg.
The most striking modification is the move from the Shimano Alfine internal gear hub to a derailleur setup. Shimano 8-speed hubs aren’t exactly known for being lightweight – they typically add over a kilogram on their own. That said, they do offer benefits in durability, protection from damage, instant shifting, and reduced drivetrain wear.
To complement the SRAM Red AXS derailleur and lightweight cassette (just 230 grams), Harvey installed a carbon fibre wheelset weighing only 1.09 kg. This drivetrain and wheel upgrade alone accounts for a weight reduction of roughly two kilograms. Swapping in Schwalbe One 1.10″ slick tyres shaved off an additional 510 grams.
Harvey also fitted a Schmolke carbon seatpost and a carbon saddle, together dropping around 400 grams. Brompton’s stock saddles are on the heavier side, so if you find a lighter alternative that suits you, it’s an easy and effective way to trim even more weight.
A carbon fibre handlebar swap shed another 200 grams from the stock G Line build, and an unexpected but significant saving came from the grips – Harvey replaced the original lock-on Brompton grips with Extralite foam grips, cutting 114 grams.
To keep the cockpit clean and add a splash of colour, HH Innovation also created a custom stem face plate with an integrated computer mount and a striking orange accent.
The braking system saw a big change too, with Extralite levers mated to TRP Spyre SLC mechanical disc calipers. Lighter Hassns Carbon rotors were also fitted, bringing the total brake system weight savings to 340 grams.
Another major contributor to the weight reduction was swapping out the original frame components. This build now sports a full carbon fibre fork and a titanium rear triangle, together cutting over 900 grams. These two aftermarket upgrades are essential for any ultralight build, as they account for a substantial portion of the overall weight loss.
The drivetrain also saw a significant overhaul. The stock cranks, bottom bracket, and chainring were replaced with a much lighter setup featuring a titanium bottom bracket, saving an additional 440 grams. Lightweight pedals shaved off another 190 grams!
Beyond the major components, Harvey fine-tuned the build with smaller upgrades – swapping out items like the luggage block, hinge clamps, pedal holder, hooks, suspension block, frame fins, and seatpost clamp – to shave off every possible gram.
Now, let’s break down the weight savings from largest to smallest.
Weight Savings Table: Lightest Brompton G Line
| Component | Model | Weight Saving (Approx.) |
|---|---|---|
| Carbon Wheels | Wheel Angel Carbon | 1700 grams |
| Removing Fenders & Rack | – | 850 grams |
| Titanium Rear Triangle | Unknown | 510 grams |
| Tyres | Schwalbe One | 510 grams |
| Removing Luggage Block | – | 480 grams |
| Carbon Fork | Silverock Mini Bro | 396 grams |
| Crankset | Cane Creek eeWings | 387 grams |
| Saddle | Gelu K3+ Carbon | 250 grams |
| Stem | Titanium | 207 grams |
| Carbon Handlebar | Schmolke Carbon | 200 grams |
| Pedals | HT Components | 190 grams |
| Seatpost | Schmolke Carbon | 190 grams |
| Brake Calipers | TRP Spyre Carbon | 150 grams |
| Grips | Extralite | 114 grams |
| Brake Levers | Extralite 3S | 100 grams |
| Chainring | Lightworks Carbon 48T | 95 grams |
| Brake Rotors | Hassns Carbon | 90 grams |
| Shifter | Sram AXS | 35 grams |
| Total Weight Saving | – | 6453 grams |
After tallying up the approximate weight savings, the lightest Brompton G Line would come in at just 8.39 kilograms. But there are a few extra items added, such as the magnetic front chain supporter, carbon rear chain supporter, and Spurcycle bell to bring the bike up to 8.5 kilograms.
How To Reduce The Weight of A Brompton G Line
By removing only the Shimano Alfine internal gear hub, heavy-duty rims, aluminium fork, and steel rear triangle, 3.5 kilograms were saved on this custom build. However, even without such extreme modifications, there are still plenty of ways for the average rider to shave weight while maintaining the original frameset and wheels.
Ditching the rack and fenders alone can bring the G Line below 14kg. Swap out components like the saddle, luggage block, handlebar, pedals, seatpost, and grips, and you’re under 13kg.
From there, the next biggest weight reduction would come from a carbon fork and titanium rear triangle, getting you close to 12kg. And that’s still with internal gears, fat tyres, and super sturdy wheels.
The next step is a carbon wheelset paired with a derailleur drivetrain, which is required to go under 10 kilograms.
Summary
The Brompton G Line was never built for lightness – it’s a practical, robust folding bike with a stiff frame, wide tyres, and an internal gear hub. But that hasn’t stopped enthusiasts from pushing its limits.
The biggest weight savings come from replacing the Shimano Alfine hub and heavy wheels with a derailleur drivetrain, carbon wheelset, and Schwalbe One tyres, cutting over 2 kilograms. A carbon fork and titanium rear triangle drop another 900 grams. Taking off the rear rack and fenders shaves a further 850 grams from the bike.
Further reductions came from a titanium bottom bracket, lightweight crankset, pedals, carbon seatpost, saddle, and small parts like grips and clamps. Even the brakes were upgraded, saving 250 grams with Extralite levers, TRP disc calipers, and Hassns Carbon rotors.