Originally Posted by
tk1971
It came with standard gearing, but thanks to the new 2013 cranks, I was able to slap a 39t Ultegra chainring for about $25 (removed 3 chain links). Now it has a similar gearing range as my MTB in middle gear (32t middle w/ 11-34t rear).
Nice bike.
To be clear, if you have the same chainring and cassette as you mountain bike, it's geared much lower. Wheel size needs to be factored in.
So your highest gear on the mountain bike would be 75.6", while on the brompton it's 46.7".
http://www.sheldonbrown.com/gears/
(gear inches is how big the front wheel of a penny-farthing would be to cover the same distance with one spin of the pedals)