Originally Posted by
OrangeKid
$500 sounds steep for a relatively minor mod.
The hub needs to be swapped. The 6spd uses a BWR,which not only has wider ratios,but the shaft has two sprocket mounts. The 3spd's BSR hub will only take one sprocket. Swapping the hub means a whole new wheel or a rebuild of the current one.
Originally Posted by
pampera
To go further, sometime ago fietsbob mentioned his schlumpf drive, but that may be expensive.
$600+ for the drive alone,IIRC.
Bromptons hold their value quite well. If you got a good enough deal on the 3spd,you might be able to sell it for at least what you paid for it,or maybe a little more. Compare the 3spd's value + upgrade cost to the cost of a 6spd. Might be worth it to just sell the 3 and get the 6. Or get the 6 then sell the 3,since unless they have the bike in stock you want,it'll take like a month or so to get one in.