The bottom bracket on my new Brompton is this one (I believe): http://www.sjscycles.co.uk/brompton-bb-cartridge-jis-for-spider-crankset-119mm-prod31207/
It is a JIS BB with 119 mm spindle length according to the description. The bike comes with 130 bcd chain ring/right crank, the crank length is 170 mm. I now want to use a shorter crank, 165 mm or shorter if available. So what cranks out there that I can use? The current crank is a single chain ring. Ideally, I want to just swap the cranks and use the current chain ring.