The Brompton factor
Bromptons account for the majority of used folding bikes sold in the UK. They are made in London, they fold smaller than most competitors, and the after-market support is better than any other folding bike brand. A twenty year old Brompton can still be serviced by any Brompton dealer, and replacement parts for almost every component on the bike are available off the shelf.
The flip side is price. A used Brompton holds its value extraordinarily well. A five year old Brompton in good condition often sells for seventy percent of the current new price. You are not paying for a cheap bike. You are paying for an engineered product that works, lasts and can be resold later with almost no loss.
Bromptons come in several gearing options. The two-speed is the lightest and simplest. The three-speed Sturmey Archer hub is the classic setup and is almost maintenance free. The six-speed combines the three-speed hub with a two-speed derailleur and gives you the widest range, at a small weight penalty. The newer twelve-speed is a more modern setup but the parts cost more when it comes time to service.
The alternatives to a Brompton
Dahon, Tern and B'Twin make folding bikes that generally fold a bit larger than a Brompton but offer more standard bike feel. If you are a taller rider or you want something that rides more like a normal bike over longer distances, a Dahon or Tern is worth considering. Parts are more standard than on a Brompton, but the fold is not as compact.
Birdy is a more premium Dutch-made folder with suspension front and rear. It folds slightly larger than a Brompton but rides far more smoothly. Prices on the used market are high and parts are specialist, so ownership can get expensive if something breaks.
Strida is the niche choice. A triangular-framed folder that collapses to a very long, thin package. They are fun to ride, very quick to fold, and quite compromised on any ride over a few miles. Worth knowing about but not for most commuters.
What to pay for a used Brompton
Under four hundred pounds you are looking at older Bromptons, usually with two or three speed setups, often in need of a service. The tyres, cables and brake pads may need replacing. These are projects that make great commuters once refreshed. Budget another hundred pounds for consumables.
Four hundred to seven hundred pounds covers the vast middle of the used Brompton market. Bikes in this range are usually five to ten years old, in good working condition, with all the common wear items still serviceable. A Brompton with a six speed drivetrain in this range is excellent value for a daily rail commuter.
Seven hundred to a thousand two hundred pounds buys newer used Bromptons, often with the current S, M or H handlebars, hydraulic brakes on the newer models, and titanium components on the higher specs. A Brompton Superlight or T Line in this range is a genuine upgrade on the standard steel frames.
Above one thousand two hundred pounds you are in Brompton Electric territory, or into the newer T Line titanium range. The Electric is a serious commuter tool if your journey has hills. The T Line is the lightest Brompton they make. Both hold their prices well.
Checking a folding bike before you buy
Unfold and fold the bike several times. The hinges should clamp firmly with no play, the latches should click into place without force, and the frame should feel solid when opened. Any wobble in the main hinge is the number one thing that can make a folding bike dangerous. Worn hinge bushes are replaceable on Bromptons but not always on other brands.
Check the wheels for true and bearing condition. Small wheels spin faster than big ones, so worn bearings are noticeable very quickly. A rumble or grinding as you spin the wheel means a hub service is due.
Look at the frame closely around the hinges and the main pivots. Check for any cracking or bulging of the paint, which can indicate a frame that has been stressed. On a Brompton, the most common wear spot is where the main frame tube meets the hinge plate. On older bikes, look for signs of repair or welding.
Finally, check the folding bike's history. Bromptons and other premium folding bikes are sometimes stolen. Every listing on Cyclesite is cross-checked against the UK's stolen-bike databases, but also ask the seller for the frame number and any receipts they have.
Living with a folding bike
The thing about a folding bike is that you actually use it. A normal bike sits locked up outside stations, in bike sheds, or at home in the garage. A Brompton goes with you. It sits under your desk at work, in the luggage rack on the train, in the back of a small car boot, and under the stairs at home. The inconvenience of folding it takes about ten seconds once you are used to it.
In the UK, a folded bike can travel on any train, any bus, any Tube, at any time of day, without restriction. That is an enormous practical advantage that does not show up in bike reviews but changes how you get around completely.
The components on a folding bike wear faster than on a full-size bike because small wheels spin faster. Plan on a new chain and rear sprocket every two thousand miles if you commute daily. Bromptons are cheap to service, cheap on consumables, and almost never suffer major mechanical failures if you keep them maintained.