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Old 03-02-13, 07:10 AM   #1
Tom_C
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Brompton with e-type front derailleur?

Hi everyone, I'm a new member to these forums but have been a reader for years. I decided to join up and start this thread because I can't find anyone who has tried fitting an e-type front derailleur to a Brompton. Can anyone think of a reason that this wouldn't work?

I believe the main difficulties with fitting a front derailleur to a Brompton are that the seat tube is too wide to fit a standard derailleur and any derailleur that is fitted fitted needs to be rotated in order to compensate for the fact that the seat tube is offset from the centre of the cranks. I'm aware of the SP front derailleur hanger that solves both of these problems, but from what I can tell an e-type should do the trick too and these can be bought cheaply online. An e-type is mounted to the bottom bracket, so it should line up with the front chainwheel without needing to be rotated.

The problems that I can envisage are:
1) E-types are normally anchored to a mounting bolt on the seat tube to help keep them in place. I've read that you can get away with not fitting this. Alternatively, the e-type could be rotated around the chainwheel so that it lines up with the seat tube and secured in position using some sort of hack.
2) The largest chainwheel that is compatible with an e-type is 44t. Not a problem, if like me, the aim is to get more low gears for hills. Also this could be compensated for to some extent by fitting a 12t rear sprocket.

Can anyone see a hole in any of my reasoning? I don't have any experience with e-type front derailleurs so maybe I've got it all wrong. It would be great to hear from anyone who has tried this approach.
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Old 03-02-13, 09:56 AM   #2
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been thinking the same but did not try it. Not sure I want a front der, i fear it`ll be crowded.
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Old 03-02-13, 10:16 AM   #3
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Clamp on brakets to use a braze-on FD, angled and offset a bit, because, on most folders,
the seat post passes behind the BB.

The bracket includes a cable housing stop,

IDK where the housing stop is on an E type to pull the derailleur.

I think it's on the frame, on the bikes that need that FD.

not too difficult to braze bracket together once the materials are gathered together..

Last edited by fietsbob; 03-02-13 at 10:30 AM.
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Old 03-03-13, 08:33 AM   #4
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fietsbob, I think e-types can come with cable housing as part of the derailleur or on the frame mount. I think I've seen seen them as top and bottom pull too. And I think you are right, bikes designed for these derailleurs seem to have braze ons to secure them to the frame, I guess to stop them rotating around the bottom bracket?

badmother, I'm not 100% sure about front derailleurs either, looking at the clearances, there doesn't seem to be much room for another chainring. I'm encouraged by the people that have had success on these forums and around the internet though. Did you start to look into the practicalities of fitting one to the Brompton? I can't believe no one has tried this - unless people have tried it and failed and so not bothered to report on it!
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Old 03-03-13, 01:02 PM   #5
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I have a bracket I got From Foldabikes, in Cal, it is a clamp on to then fit a braze on FD.

Steve Parry in UK has similar.

I liked the MD crank better.. $C and i'll sell the FD; Bracket and Thumbshifter to go on the bars.


Quote:
unless people have tried it and failed and so not bothered to report on it!
or just did't report it, conveniently, Here.

one thing I see, [mechanic-think] adding it under the fixed cup moves the chain line off, alignment.
then you have to correct for that.,

presumably the double crank and new BB that you buy you will sort that out.

Dive in and then, make the report.. Tom.

BTW, no 12t for the AW3/BSR,only the no IGH 1~2 cog;.. or 6 speed BWR hubs.

BTW, Todd , partner in the PDX Brompton dealership, toured with just a change of crank
to 36,44t on his 6 speed , heel works to down shift, up shift done, stopped,
with fingers, when needed.

Last edited by fietsbob; 03-03-13 at 01:19 PM.
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Old 03-03-13, 05:42 PM   #6
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Quote:
Originally Posted by Tom_C View Post
fietsbob, I think e-types can come with cable housing as part of the derailleur or on the frame mount. I think I've seen seen them as top and bottom pull too. And I think you are right, bikes designed for these derailleurs seem to have braze ons to secure them to the frame, I guess to stop them rotating around the bottom bracket?

badmother, I'm not 100% sure about front derailleurs either, looking at the clearances, there doesn't seem to be much room for another chainring. I'm encouraged by the people that have had success on these forums and around the internet though. Did you start to look into the practicalities of fitting one to the Brompton? I can't believe no one has tried this - unless people have tried it and failed and so not bothered to report on it!
After reading a lot I am under the impression that most peopel that add a second chainring in the front end up doing the "greasy fingers" shifting, or learn to "kickshift" at least from the big down to the small.

I guess most of us are more eager to report on our sucsess, that when we fail. Also I think when something is not right we do some thinking- then some thinkering- then some thinking- and more thinking until we forget about the whole project. At this point we have started planning the next project..

Are you thinking of doing this mod on a three or six speed? I can see the point on a three speed, especially an old frame with no der. option. On a six speed you would play with three shifters and shifter cables needs adjusting.

On a five speed (one cable) hub again, same as a three speed, may be worth it but use a gear calculator first and decide after that. I think I remember you only get 7 gears (becouse of overlapping) and in that case it may be better to go for a 7 or 8 gear hub. Depends on what you need and what you have.

If you only need some extra gears in hilly areas you may want to finger shift.

Remember it is a folder. If you fold it a lot and travel with it a der can easily be whacked out of position on a weekly basis, we are talking millimeters here.

Do some reading and searching (like in the Yahoo Bromptonforums) and find out what others have learnt from theyr mistakes. Keep us informed if you try it!

Last edited by badmother; 03-03-13 at 05:46 PM.
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Old 03-05-13, 06:04 AM   #7
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Hi Badmother, wise words about the potential for knocking the derailleur, I do use my Brompton mainly for the commute and it gets folded and chucked around trains quite a lot. I guess there's a reason many people settle for the greasy fingers option. I have a 2012 3-speed and have worked out that with 44t and 38t chainrings and 13t rear sprocket I can get a gear range of 35"-73" with quite even 15% steps between gears with no overlaps. Funnily enough, thats almost exactly the same gear inches and step sizes as the Shimano Nexus inter-7 hub, but without the highest gear (84") and obviously without the simple linear shifting. I have the Nexus hub on another bike so I know I would like the range and step sizes if I got it to work on the Brompton.
I've been thinking (and thinking) about this idea for a while and I'm thinking you are right, I either need to take the plunge and go for it, or just drop it and move onto the next project! One of the delays is I have been waiting for the 2013 cranksets to become available. I don't want to go through the lengthy trial and error process of finding a double chainset that will give a decent chainline without compromising fold etc.

I'll report back here whether I succeed or fail. If it doesn't work at least I might save someone else the hassle later on!
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Old 03-05-13, 10:16 AM   #8
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I see a crank spider on the new crank as made to only have a chainring on the inside face of It.

so another crank with the same 130 bolt circle, may be more suitable..
just pick the BB length to dial in the chainline.


some who added a granny to the standard arm, swaged to the chainring,
found the added MA, torque, loosened the connection ..

Last edited by fietsbob; 03-05-13 at 10:38 AM.
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Old 03-05-13, 10:42 AM   #9
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I am also waiting for the new crankset (but I also want the option of two rings) and I really llike Nexus 7 hubs. I tend to find them on dumpsterbikes and there is no way I`ll find one with drum brake around here. I need to look into rebuilding a coasterbrake one to a narrower "drumbrake -minus drumbrake Nexus7". Hmmm. Back to thinking and planning..
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