Rear rim's just cracked.

[berlinonaut]

So am I right in understanding that newer Brompton rims have a black line that appears as a wear indicator?

I've not yet managed to break through one of Brompton's double wall rims. Some say the'd have an internal wear indicator - when you see it it's time to change the rims. With the older single wall rims it depends from the age: Some had an external ring (once it's gone time for a change), others had nothing. Brompton used several different rims over the years with the single wall. Thus these older experiences are neither consistent nor can they used 1:1 on the double wall rims they use since 2013.

 

[Kell]

Some say the'd have an internal wear indicator - when you see it it's time to change the rims.

I didn't take a picture of mine this time around, but there was no other indication that it was about to go. The wear indicator was not visible anywhere, there was just the split.