On my cycle back through Hyde Park earlier in the week, I noticed my Brompton was making some odd noises. "Odd" in the sense that it had not been making them before, and I hadn't heard other bikes making them, but potentially perfectly normal for a Brompton since I've only had one for a couple of weeks.
I popped it up on the stand yesterday to take a look, and to do some normal bike maintenance.
There were two noises — a rattling noise from the hub, and a rubbing noise from the front type.
Rattling noise from the hub
I'm not convinced I've fixed this, but oiling the chain, and hub, and cycling through the gears, seems to have made a difference. I only had time for a quick test ride, and it did seem quieter.
Looking online, the general consensus seems to be that, if it is changing gears smoothly then, even if it is making a noise, it's probably fine.
That worries me slightly, but, since I don't plan on taking the hub apart, I'll leave it for now and see what happens.
This was the noise I had heard most when cycling, and it was a simple one: the front mudguard had got clogged up with mud and other detritus from the wet road. Clearing that out made an immediate difference.