It’s October and the dirt season has begun in Southern Finland. We get a lot of rain and wind, making for very dirty road conditions. I recently, for the first time since starting to use the Brompton back in March, encountered some issues with the gears not shifting properly in wet conditions. A view to the moving parts revealed the likely reason for that:
Turns out that the design of the plastic chain guides is prone to collect all kind of dirt, which then negatively affects the shifting between the small and the large sprocket.
Cleaning this out was quite a bit of work, as just using a brush was not enough; I had to peel the sand out of all kinds of little openings and edges. But now the gears are working fine again – until the next rainy day, I presume. (I might also try to use a dry chain oil instead of wet lube, which always tends to collect more dirt.)