Technology

Technical Details
In the beginning: All screws of the Brompton are metric! So be not concerned about repairing or spare parts. At british engineers one thinks first about inch and yards...
The Brompton rolls on 16"-wheels (there we have it now). Because the tubes have car valves, they can be pumped easily to nearly 4 bar at the petrol station. The rear wheel has a suspension: The rear wheel assembly is fixed revolving at its lower end and leans on the mainframe by a rubber element at its upper end (in the picture at right marked with squares).
Here some more technical details:

Mainframe: Steel
Hinges: forged
Weight: 12 - 13 kg
Folded size: 56x55x25 cm
Wheels: aluminium alloy rims
Tires: 16 x 1 3/8" (37-349)
Wheelbase: 1015 mm
Saddle height: 760-980/1075 mm
Bottom bracket height: 270 mm
Handlebar height: 1015 mm
Steering angle: 72.4°
Gearing 3-speed: 3.83 - 5.11 - 6.80 m
Gearing 5-speed: 3.37 -4.04 -5.11 - 6.44 - 7.66 m

Tips and Tricks
The following section is for those who have already a Brompton. Who is unsure about buying a L-Model gets tips how to equip it with lights here.
Build on lights
The biggest disadvantage of the L-models is the missing lights. In Germany it seems to be "cool" (especially for young people) to drive without lights. Therefore I want to advise you to build on and use lights at your Brompton. Because the lights are in a quite low position I recommend additional reflecting stickers at the handlebars and the top of the seat pillar. I am also on the way as car driver and look especially after cyclists. During bad weather even I have problems to recognize bicycle drivers. How much more dangerous is the situation for the bicycle drivers caused by the naively and mostly too fast driving of other car drivers!? So: Lights on!
Back to Brompton: At right you see how I build on the dynamo: At the left side of the rear wheel swing. Because of this it is situated at the outside of the folded Brompton. This is a small disadvantage, especially because I use a Nordlicht-Dynamo. This collides with the left crank if one doesn't look out. Before that I used smaller dynamos, but they broke quickly at bad weather. You get used quickly to lift the crank before folding in a position that it doesn't collide with the dynamo.
At the T-Brompton the dynamo is mounted at the right side on a stable girder of the rear carrier. Because of this it is situated in the inner parts of the folded Brompton, like all other dirty or sensitive parts. This is not possible with the L because of the lacking rear carrier.
The front light is mounted quite simply. It is screwed to a sawed normal holder fixed to the long screw of the front brake. Normal holders, which you can buy are all too long. All parts you mount have to fit also with the Brompton folded! I looked for a holder which was after sawing still strong enough that I could drill the holes for the fixing of the light.
The rear light made more problems for me. At the L-model the rear carrier is missing, which works as a solid base for mounting dynamo and light (see "Models"). I found this solution: Sawing a normal rear light, so that only the upper part with the lamp remains. Screwing and glueing this to the rear reflector of the L-model. An even better solution is to buy a socalled "Toplight" and to mount it instead of the normal reflector. Both methods have the disadvantage of the rear light bumping to the ground if the Brompton is folded. The reason for this are the too small standard castors (rollers) on which the folded bike stands. So:
Enlarge the castors for standing
This meanwhile a standard modification. Replace the too small plastic castors by bigger ones. I simply used wooden castors with a rubber ring. They are available in every do-it- yourself shop. The hole is quickly drilled to fit. In the pictures at right you can see the effect. I just should paint my castors black again...
Practical in strange towns
Often I drove through strange towns and had to look to the city map very often. The clip in the picture at right is simply fixed with sticky tape. It made the handling of the map much easier.
Mudguard extension
During fast driving in the rain the rear mudguard is not long engough. After I was totally dirty after my first Brompton ride (at the borrowed Brompton also the front mudguard extension was removed...), I invented the mudguard extension. Buy a normal plastic mudguard and shorten it. Saw and file a hole into it, so that it exactly clamps to the small castor. At right you can see it. After folding I put the extension between front mudguard and front wheel. This works for more than two years now!
What's squeaking here?
At some time I always heard a quiet squeaking during driving. That was quite nerving. Mainly it appeared during stepping on the pedals and I had the crank bearing under suspicion. But then sometimes I could hear it when I was just rolling. What was it?
At some time I discovered that it came from the rubber element of the suspension. It has a screw inside which just had to be oiled.