The Brompton folding bike was designed and built in London in 1975 by Andrew Ritchie in his flat in South Kensington opposite the Brompton Oratory. Still made in London today.

The Brompton is very popular in city ride, the offical brompton has 4 options for the gears: single speed, 2-speed, 3-speed(internal gear), 6-speed(internal gear).

The most popular is the 6-speed, but with a heavey 6-speed internal gear hub, the whole bike is heavy, so many riders would choose the 2-speed which much lighter.

But the 2-speed can't fit for a long trip, so the 3/4-speed was designed to upgrade the 2-speed, let's see the difference from the photos:

1. The 2-speed and 3/4-speed free hub with different design.

2. The 3/4-speed free hub similar the 11-speed short version.

3. The 2-speed only can with 2 gears, the 3/4-speed can with 2 or 3 or 4 gears.

    So exact is 3/4-speed hub can use 2-speed or 3-speed or 4-speed.

4. The 2-speed use a spring lockring, the 3/4-speed use a normal lockring.

5. For hubsmith hub, the 2-speed and 3/4-speed free hub can exchange.

If want to change 2-speed to 3-speed or 4-speed, also need to change the shifter etc.

Now few 3/4-speed shifter for brompton on the market, but can use some others example shimano.

Change 2-speed to 3-speed or 4-speed need many professional knowledge, it is best do in bike shop.