Folding Bikes - question about brompton 6 speeds...

i was looking at the brompton specs for 6 speed and from bfold, it states "This bike uses Brompton's time proven 6 speed internal hub and derraileur combo." so what kinda hub is it? is it a sturmey archer or it's own propriertary part?

and how does it compare to a bike that is straight up derailleurs or hub vs this combo derailleurs and hub? what are the pros or cons? or maybe there is no cons for this combo system and brompton come up with a system that is best of both world?

I also wanted to get a 6 speed however after finding more about it I decided against.
It`s a 3-sprocket hub and 2-sprocket derailleur design controlled by two switches, one on each handle and you need to change position of both to move up or down by one gear only. It might be possible to get used to it but it is not an smart solution if you ask me. Instead I am now convinced to get a 3 speed hub only since it is simple and since I will also add an electric motor to the front wheel so I can do away with more gear options.

The hub was SRAM but now it should be the new wide range hub from BWR.
Check here: http://www.ecovelo.info/2008/09/17/brompton-6-speed-wide-range-hub/

3 speed hub
file:///C:/Users/Okapi/AppData/Local/Temp/moz-screenshot.jpghttp://foldingbikes.simbahosting.co.uk/Brompton%20files/Brompton%20parts/3_Speed_SA_Hub.jpg

6 speed hub with derailleur design
http://foldingbikes.simbahosting.co.uk/Brompton%20files/Brompton%20parts/6_Speed_Brompton_Wide%20Range_Hub.jpg


6 speed BWR hub cut-away view
http://foldingbikes.simbahosting.co.uk/Brompton%20files/Brompton%20parts/BWR_cut_away_shot.jpg

The BWR hub is made by Sunrace Sturmey-Archer but designed by Brompton and meant to be used with their 2-sp derailleur. It is difficult to get as wide a range in so light and compact a package using any other gearing arrangement.

For the 3 speed hub. Can you swap out the 3 speed sram hub and repace it with the 8 speed sturmey archer hub? Is this possible and has any1 done it? Is it easy?

Also what is the reason for brompton to use a derailleurs and hub combo?

Bromptons way of doing it keeps everything compact,with straight chainline.I've had a derailer type folder and find on conventional derailers they tend to need alot of adjusting after being folded,Brompton avoids that by doing it the way they do.Also by useing hub gears theres far less serviceing needed.

LWaB is wondering on why Brompton use a combo' not a hub.Me Too. I wonder why they do not offer an 8 speed hub without a derailleur. On the other hand, for younger and athletic persons or electric bikes 3 speed is even better anyway.

So has anyway tried to change the 3 speed sram hub to a 8 speed sturmey archer hub? Is this possible?

The UK bike shop Kinetics, run by Ben Cooper does fit bromptons with the SA 8 speed hub. Why would brompton choose such a combi? I tink the 3 speed hubs are more durable than the 8 speeds. And the current combo is lighter than an 8 speed hub i tink.

It has been done, 8sp hubs by Ken Cooper as well as 14 Rohloff by Steve Parry. Sounds good on paper, but the Brompton ends heavy, with a wide rear triangle.

Even though I am a big fan of evolution and would love to see the Brompton company offering more options for their bikes, the technology to make a Brompton more geared and still be compatible with the basic concept of the bike portable, dynamic, light) is yet to be revealed.

Maybe this new Rohloff that we heard about might be the near future answer...

The derailleur is really just a slightly modified chain tensioner, which is there on all Bromptons, even single speeds. The 5 speed hubs that used to be available were inefficient and unreliable. A better solution was to double the range of the existing 3 speed hub by modifying the existing chain tensioner - minimal weight increase, and simple from an engineering perspective, if a bit confusing for some to use.

LWaB is wondering on why Brompton use a combo' not a hub.


No, I am not.

Brompton is not sufficiently satisfied with the alternatives. None of the hubs with more than 3 gears are as light as Brompton's 6 sp set-up. We can discuss alternatives but one of the major complaints about Bromptons is that they are too heavy. Virtually any alternative will increase the weight.

.........
Also what is the reason for brompton to use a derailleurs and hub combo?

http://www.brompton.co.uk/page.asp?p=3067

"Why aren't there more gears on your bikes? Why do you use hub gears?"

It has been done, 8sp hubs by Ken Cooper as well as 14 Rohloff by Steve Parry. Sounds good on paper, but the Brompton ends heavy, with a wide rear triangle.

Even though I am a big fan of evolution and would love to see the Brompton company offering more options for their bikes, the technology to make a Brompton more geared and still be compatible with the basic concept of the bike portable, dynamic, light) is yet to be revealed.

Maybe this new Rohloff that we heard about might be the near future answer...

Just from memory, I think that the difference between a SA3 and an SA8 hub is approximately 500 grams; probably less than the rear rack. I think the high-end Shimano 8-speed hubs are comparable in weight to the SA8 but better performaning. Maybe there are width, efficiency and robustness reasons for sticking to the three speed, but I find it surprising that 500 grams on a 20-30 pound bike is what stops Brompton from offering the option.

Mind you, it isn't clear whether width is an issue either. A 25mm wider hub -- I'm assuming 135, but it could be less in practice since there are people who remove spacers to fit hubs into a narrower OLD and some 8-speed hubs are less than 135 -- would only widen the fold by 12.5mm since the most exterior point on the non-drive side is the pedal. Some fiddling with stuff on the drive side might ameliorate the 12.5mm on the drive side too. But this could get complicated with chainline issues and the such. So the 12.5mm ... half an inch ... is a conservative estimate.

http://www.brompton.co.uk/page.asp?p=3072

I wouldn't be surprised if there were production/cost issues for offering bikes with different OLDs or more hub options relative to their demand. But the engineering is there and in plain view, IMO.

"This bike uses Brompton's time proven 6 speed internal hub and derraileur combo."

Time proven? Didn't the BWR hub debut this past January?

tcs

You can get used to changing stangest gears in a single day. So my d'sl'ke 's not because it is difficult or something: I think its not an elegant way to use two shifters in a zigzag setup' therefore a 3 speed is better. This is just me.

The Brompton 6 speed is worth the extra and works great. it is efficient and reliable. The only thing I dislike about it is the design of the 2 gear shifters on each side!