I'm hearing a ticking noise coming from my Brompton. It's only when pedalling. It's the same under load or light pedalling, and it's the same in all gears (it's 6 speed). It's more frequent and irregular than crank speed, and slower than wheel speed. Sometimes I think I can feel it through the cranks.
I've had a look and can't see anything amiss. I checked the chainring bolts, greased the bolt in the suspension block, and poked and prodded for anything loose or contacting something it shouldn't. No joy. The BB doesn't seem to have any play. The bike is only a few months old.
Any suggestions?