On Monday morning I rode to work from Macclesfield on the Brompton. The whole ride was accompanied by a chorus of squeaks which was very irritating. I eventually managed to trace the sources of the squeaks down and fix them, and I present them here for the benefit of other Brompton owners.
1) Not a Brompton issue per se, but the B67 I got for Xmas which is currently residing on my Brompton has passed through the initial “Hard” phase and is now in the “Creaky” phase. With the B66 on the DL-1 this was not really an issue, because there is little other noise from the bike I just ignored it and it went away.
The creaking is not caused by the springs as you might expect, but by the leather rubbing on the metal pads on the underside to which it is riveted. A bit of lubrication sorts this problem out, the approach I took was to melt some Proofide in a teaspoon with a match, pour it onto the interface between metal and leather and slightly stress the saddle so that it can easily get into the gap.
2) The Rear brake cable and gear cable were rubbing on the side of the tyre when under hard pedalling. This was fixed by using a few cable-ties to hold the cables in a favourable position within the cable-gathering loop on the right seat-stay.
3) It turned out that the main source of the racket was the suspension block, with the saddle acting as a sort of speaker for the noise it generated. The suspension block is held onto the rear triangle by a single bolt, which once removed allows the block to be detached and disassembled. I lubricated the entire length of the bolt with lithium grease and re-attached the suspension block to the bike. I also tightened the bolt much futher than it had been when previously, resulting in a firmer, more compressed block which moves less.
These three tweaks have effectively eliminated the noise from the Brompton, so I can now get on with the business of enjoying the ride instead.