Modding a Brompton B75

[Tenkaykev]

There are a few hills near place I work and I see many riders with different bromptons (and all sorts of other bikes for that matter) zipping past all day long. It seems for some of them it is a bit of a challenge (they pedal leaning forward from a seat) but some of them are able to do it while seated. I am trying to see what is this related to - 6 speed broptons, higher fitness of the driver, moving inertia (just the right moment trough traffic lights) or anything else. One thing that I noticed is that it seems that B75 is not so common among the drivers. Or I would have seen it with it's distinctive color.

Perhaps they have different handlebar types. The "M" and "H" bars are higher and give a more upright position. The "S" bars are lower and give a "sportier" more aggressive position. Being in the correct gear can also make a difference, especially in traffic with constant stopping and starting, being in too high a gear can lead to having to "mash" the pedals.
There's also the possibility that some of the Bromptons you see are Electric and the Pedal assist lets you remain seated while the motor takes up a lot of the effort.
EDIT:
If there's a lot of hills locally, then you can specify a 44 tooth chain wheel which is a 12% reduction from the standard 50 toothed chain wheel and will make the hills easier to negotiate.

 

[rogerzilla]

The B75 is fairly new and is a bit of a parts bin special. Apart from the mudguards, you're not missing anything important, so it is a good choice. Most people like the colour.

 

[yoho oy]

Perhaps they have different handlebar types. The "M" and "H" bars are higher and give a more upright position. The "S" bars are lower and give a "sportier" more aggressive position. Being in the correct gear can also make a difference, especially in traffic with constant stopping and starting, being in too high a gear can lead to having to "mash" the pedals.
There's also the possibility that some of the Bromptons you see are Electric and the Pedal assist lets you remain seated while the motor takes up a lot of the effort.
EDIT:
If there's a lot of hills locally, then you can specify a 44 tooth chain wheel which is a 12% reduction from the standard 50 toothed chain wheel and will make the hills easier to negotiate.

London, land of bromptons... Most of the bikes I see are M bars, not electric, I think I would have spotted electric ones by their distinct front bag and motor hub. I spotted just one with butterfly type of a bar. It is hard to say from a distance how many gears these bromptons have. I would guess that most of them 6 speed. I had difficulty spotting B75 type gear shifter or it seems that there is something more going on on a left side bar than just a break handle. It is hard to see from a distance, but either most bromptons are relatively new or probably 6 speed.

 

[rogerzilla]

The current 6 speed has gears that are just about as gappy as the 3 speed, but with almost twice the range. That wouldn't make a bike faster, except down big hills. The old 6 speed had much closer gears and could be faster when ridden by someone used to a normal bike, as it is easier to find the "right" gear for the conditions.

 

[alicat]

The current 6 speed has gears that are just about as gappy as the 3 speed, but with almost twice the range. That wouldn't make a bike faster, except down big hills. The old 6 speed had much closer gears and could be faster when ridden by someone used to a normal bike, as it is easier to find the "right" gear for the conditions.

Just curious when the change was made? My late 2009 P6R seems okay.

 

[rogerzilla]

Just curious when the change was made? My late 2009 P6R seems okay.

Late 2000s, I think, when the BWR hub became available. The old 6-speed was based on the SRAM T3, which has an internal ratio of about 1.36:1, not much more than a Sturmey-Archer SRF3, BSR or AW. The derailleur (in both types of 6-speed) fills the gaps between the hub gears and gives you one extra.

 

[alicat]

Thanks @rogerzilla. I think I've got the BWR. It seems okay to me.

 

[berlinonaut]

If there's a lot of hills locally, then you can specify a 44 tooth chain wheel which is a 12% reduction from the standard 50 toothed chain wheel and will make the hills easier to negotiate.

The B75 already has the shorter gearing:

Gear Ratio: -12% gearing as standard