Brompton 3 to 6 Speed Conversion
#1
Senior Member
Thread Starter
Join Date: Aug 2012
Location: The Big City
Posts: 619
Bikes: Brompton M3L, Tern Verge P20, Citi Bike
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 85 Post(s)
Likes: 0
Liked 9 Times
in
7 Posts
Brompton 3 to 6 Speed Conversion
I'm thinking of having my Brompton converted from 3 speed to 6 speed, and am wondering if anyone else has done that. How much did it cost? Did you do it yourself? How did it work out?
I understand this conversion is pretty expensive. I've seen kits online sold in England, but none in the United States. Can you get the kit in the US, or source the parts? And how hard is it to do? I think doing the work would be beyond my wrenching skills, but I'm wondering how hard it would be.
I got my Brompton second hand from a friend, barely used and for a great price, so I can't complain, but I would have chosen a 6 speed (and a different color). Part of me is tempted to get a whole new Brompton just the way I want it; that would be an extravagance, but a tempting one.
I understand this conversion is pretty expensive. I've seen kits online sold in England, but none in the United States. Can you get the kit in the US, or source the parts? And how hard is it to do? I think doing the work would be beyond my wrenching skills, but I'm wondering how hard it would be.
I got my Brompton second hand from a friend, barely used and for a great price, so I can't complain, but I would have chosen a 6 speed (and a different color). Part of me is tempted to get a whole new Brompton just the way I want it; that would be an extravagance, but a tempting one.
#2
Senior Member
Join Date: Jun 2008
Posts: 449
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
The cost difference between a 3 spd and 6 spd is less than $100 for a new bike. Contact a shop and see what they would charge to upgrade your 3 to a 6 and figure anything over $100 is $ that would make up part of the difference between what you would sell your bike for and a new one. Some people don't want to wait 2 months for a new one and would like to save some $ on a used one. Maybe you should research used prices and see what you might expect to sell yours for. It may make moving on to a new one reasonable or perhaps the cost difference would stll be more than you are willing to go. Worth looking into.
#3
Banned
S-A S-RF5(N) would build up as a single lever 5 speed .. and a 2 lever 10 speed ,
since it uses the 9 spline driver of the BWR hub they make for Brompton.
I went with a Schlumpf Swiss Mountain drive Crank, it's 2 speeds are widely spaced so the 3 hub gears are used twice.. 6 speeds.
If you want the conversion parts in the US talk to the dealer ..
since it uses the 9 spline driver of the BWR hub they make for Brompton.
I went with a Schlumpf Swiss Mountain drive Crank, it's 2 speeds are widely spaced so the 3 hub gears are used twice.. 6 speeds.
If you want the conversion parts in the US talk to the dealer ..
Last edited by fietsbob; 12-25-14 at 12:57 AM.
#4
Part-time epistemologist
Does the 6 speed conversion work with all of Brompton's three speed hubs?
__________________
A narrative on bicycle driving.
A narrative on bicycle driving.
#5
Banned
Now, Its a different.. wider ratio hub BWR.. the successor to the AW3 is the BSR
the 9 spline driver is another Shimano created standard on the BWR adoptedfrom Shimano's BMX hubs
the 3 speed uses the 3 spline cog that S-A has almost-always used .. the Mk 3, 6 speed Brompton went to Sachs , in Germany then,
they used the 3 spline cog type, in 3/32" thickness .. a different driver for their Torpado 3 speed .. to take 2 cogs ..
the 15t was made as a skip tooth .. 1 in 5 was shorter.. , so the chain would shift over it.
I use the 15t, alone, all that will fit .. on my M3L
(edit: N/M)
the 9 spline driver is another Shimano created standard on the BWR adoptedfrom Shimano's BMX hubs
the 3 speed uses the 3 spline cog that S-A has almost-always used .. the Mk 3, 6 speed Brompton went to Sachs , in Germany then,
they used the 3 spline cog type, in 3/32" thickness .. a different driver for their Torpado 3 speed .. to take 2 cogs ..
the 15t was made as a skip tooth .. 1 in 5 was shorter.. , so the chain would shift over it.
I use the 15t, alone, all that will fit .. on my M3L
(edit: N/M)
Last edited by fietsbob; 05-08-14 at 09:07 AM.
#6
DancesWithSUVs
Join Date: Apr 2005
Location: Griffin Cycle Bethesda,MD
Posts: 6,983
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Likes: 0
Liked 2 Times
in
2 Posts
The BWR hub used for the 6 speed takes two cogs,the regular BSR hub only takes one. The BWR also has a wider(40% vs 36% IIRC) jump between gears,FYI.
__________________
C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L/S2E-X
C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L/S2E-X
#7
Banned
3 speed , plus, Schlumpf MD crank makes it into a wide spread 6 speed .. it will Climb mountains as if a 50,20t double
the BWR with 13 & 16t cogs halfsteps the hub 3 ..
the BWR with 13 & 16t cogs halfsteps the hub 3 ..
#8
DancesWithSUVs
Join Date: Apr 2005
Location: Griffin Cycle Bethesda,MD
Posts: 6,983
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Likes: 0
Liked 2 Times
in
2 Posts
...for only about $700.
__________________
C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L/S2E-X
C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L/S2E-X
#9
Senior Member
Join Date: Apr 2009
Posts: 114
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I suggest you resale the bike and buy a new 6 speed. I find the old 3 speed brompton doesn't have the nice ride as the new 6-speed - too slow for my liking and not good with hills in my area.
#10
Banned
if you can spin out a 54:13 in high, you should be moving at a sufficient rate of speed ..
Ok the BWR will take a 12.. so will the S-A S-RF5(N). which is also using a Narrow, axle, and 28 spoke.
which has a taller internal 5th gear..
Ok the BWR will take a 12.. so will the S-A S-RF5(N). which is also using a Narrow, axle, and 28 spoke.
which has a taller internal 5th gear..
#11
Part-time epistemologist
Well the OP might want to check that he has the right type of hub then.
__________________
A narrative on bicycle driving.
A narrative on bicycle driving.
#13
Banned
or stack all that on the S-A S-RF5(N) .. , add a double or triple crank .. really Go Go Gadget !
Last edited by fietsbob; 05-12-14 at 09:22 AM.
#14
Senior Member
Thread Starter
Join Date: Aug 2012
Location: The Big City
Posts: 619
Bikes: Brompton M3L, Tern Verge P20, Citi Bike
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 85 Post(s)
Likes: 0
Liked 9 Times
in
7 Posts
Thanks for the input. Word from the bike shop is that parts for the job comes to $363. That plus labor means the cost of conversion will push $600. So it looks like I'm looking at another Brompton. Or possibly another bike of some sort (A Bike Friday? A Turn?).
Just this weekend, I took the bike out of town and did a hilly ride (a round trip so two in fact). I survived, but I had to walk a couple of short stretches, did some standing on the pedals and pulling on the handlebars, and I cursed my lack of a lower gear. On the other hand, the three speed is good enough, quite nice even, for 90%+ of the riding I do, so there isn't a lot of urgency to upgrade, which means I can dither for a long time. But the itch to get something better is becoming more persistent. The trouble is, I live in a closet of a NYC 5th floor walkup apartment, so the bike has to be a folder.
Just this weekend, I took the bike out of town and did a hilly ride (a round trip so two in fact). I survived, but I had to walk a couple of short stretches, did some standing on the pedals and pulling on the handlebars, and I cursed my lack of a lower gear. On the other hand, the three speed is good enough, quite nice even, for 90%+ of the riding I do, so there isn't a lot of urgency to upgrade, which means I can dither for a long time. But the itch to get something better is becoming more persistent. The trouble is, I live in a closet of a NYC 5th floor walkup apartment, so the bike has to be a folder.
Last edited by wilfried; 05-12-14 at 12:42 AM.
#15
Banned
My Mountain drive crank gets me an 17" low gear with a 54 /15 BSR .. the reduction gear is as if the crank has a 21.6t granny gear
when kicked into low range .. Yea it comes in at about $600.
3rd to 4th double shift is Quick since both gears are internal , at any speed even stopped
So 4th to 3rd bogged down on a hill is an easy shift..
There is also the option of fitting a double crankset of conventional type, and use the heel of your shoe to dislodge the chain from it's Big Ring .
that could be more affordable.. You already have the chain tensioner
when kicked into low range .. Yea it comes in at about $600.
3rd to 4th double shift is Quick since both gears are internal , at any speed even stopped
So 4th to 3rd bogged down on a hill is an easy shift..
There is also the option of fitting a double crankset of conventional type, and use the heel of your shoe to dislodge the chain from it's Big Ring .
that could be more affordable.. You already have the chain tensioner
Last edited by fietsbob; 05-12-14 at 09:03 AM.
#16
Banned
Actually they (assume you found the picture , not your bike,) fitted that to what was a 2 speed hub so only gained 1 more gear.
Lower right corner ... it's not the BWR
#17
Senior Member
Thread Starter
Join Date: Aug 2012
Location: The Big City
Posts: 619
Bikes: Brompton M3L, Tern Verge P20, Citi Bike
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 85 Post(s)
Likes: 0
Liked 9 Times
in
7 Posts
I don't thing a double chain ring is an option, since we're talking mostly rolling hills, short stretches of steep climb followed by downhills or flats. I'd hate to have to get off the bike to switch chain rings on top of every hill.
Fietsbob, how did you get the third sprocket on the bike? Googling wasn't very effective. Are there instructions somewhere online?
How hard was it to obtain and install the Mountain Drive?
Fietsbob, how did you get the third sprocket on the bike? Googling wasn't very effective. Are there instructions somewhere online?
How hard was it to obtain and install the Mountain Drive?
#18
Banned
Cycle Monkey in Berkeley is a US Distributor/retailler , but I expect Nyce wheels in NYC can get them .
Mine came thru CM Wasson in California..
there is a lot of torque developed in Low range, but the special model for Bromptons transfers that torque
thru a lever with a Button that rests on top of the part behind the crank that carries the rear fold pivot ..
I needed no frame modifications on my Mk4 bike .. the BB is part of the whole crank assembly
as the shift is a shuttle pin passing thru the BB spindle center . center button is the shift from one side to the other .
conic rings center the BB assembly in the shell .. it screws into itself not the threads in the BB..
FWIW there is a 1.6x overdrive version, 'Speed Drive' , when fitted with a 34t chainring , in high range it acts as if you fitted a 54t chainring too.
It does take a chamfering of the edge of the BB shell*.. there is less torque in the overdrive against the frame , so the friction
of a gripper washer in aluminum between the frame and the crank is sufficient..
* not for the first time , Mavic had a BB assembly requiring the bike frame edge be conic rather than flat across the face.
Brompton already has a BB shell face that is not exactly flat, so the chamfering is not removing much metal.
and why the fitting of the MD really didn't require, any ..
its not my bike , I just saw the way it looks .. the Brompton 2 speed is a hub with no internal gears
so there is a more hourglass shape to it . and a different way the driver is attached to what is a short driver freehub.
9 spline driver style is shared by the 2 and 6 (IGH 3) but not the BSR/AW3..
It can be done with 2 thinner spacers and Shimano Cogs .
there are custom adapters *, by the way to bolt on what is a braze on FD where the seat tube is .
it is placed behind the Seat tube a ways, since the seat post telescopes down behind the BB..
* Steve Parry in UK has some ,( a brompton modifier) I got one that the Wasson Shop got made ,
I Can resell, it .. , a Thumb shifter and a Bz on Ft Derailleur .. makes it work .
Mine came thru CM Wasson in California..
there is a lot of torque developed in Low range, but the special model for Bromptons transfers that torque
thru a lever with a Button that rests on top of the part behind the crank that carries the rear fold pivot ..
I needed no frame modifications on my Mk4 bike .. the BB is part of the whole crank assembly
as the shift is a shuttle pin passing thru the BB spindle center . center button is the shift from one side to the other .
conic rings center the BB assembly in the shell .. it screws into itself not the threads in the BB..
FWIW there is a 1.6x overdrive version, 'Speed Drive' , when fitted with a 34t chainring , in high range it acts as if you fitted a 54t chainring too.
It does take a chamfering of the edge of the BB shell*.. there is less torque in the overdrive against the frame , so the friction
of a gripper washer in aluminum between the frame and the crank is sufficient..
* not for the first time , Mavic had a BB assembly requiring the bike frame edge be conic rather than flat across the face.
Brompton already has a BB shell face that is not exactly flat, so the chamfering is not removing much metal.
and why the fitting of the MD really didn't require, any ..
Fietsbob, how did you get the third sprocket on the bike?
so there is a more hourglass shape to it . and a different way the driver is attached to what is a short driver freehub.
9 spline driver style is shared by the 2 and 6 (IGH 3) but not the BSR/AW3..
It can be done with 2 thinner spacers and Shimano Cogs .
there are custom adapters *, by the way to bolt on what is a braze on FD where the seat tube is .
it is placed behind the Seat tube a ways, since the seat post telescopes down behind the BB..
* Steve Parry in UK has some ,( a brompton modifier) I got one that the Wasson Shop got made ,
I Can resell, it .. , a Thumb shifter and a Bz on Ft Derailleur .. makes it work .
Last edited by fietsbob; 05-12-14 at 10:36 AM.
#19
Senior Member
Join Date: Aug 2012
Location: NYC
Posts: 2,380
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 151 Post(s)
Likes: 0
Liked 10 Times
in
8 Posts
text from the page:
"This Ti cassette system will turn your 2 speed into a more versatile 3 speeds and turning a 6 speed BWR driven Brompton into a 9 speed monster.
The concept is not new (giving the Brompton extra speed), but the idea to make it effectively working for everyday DIY-er’s being able to install this at home without much of the heavy machining and customizing had to be the first.
The system will come with 3 pieces of Ti cassette sprockets, a Ti replacement tensioner wheel’s roller and a custom made 3 speed shifter that is made out of aluminum alloy.
There are 2 different speed group that is begin offered. They are the 19T-16T-13T set, which gives a better and easier climbing experience. Where the 18T-15T-12T set offers a faster riding experience.
Please note that this cassette system requires certain experience with bicycle hardware installation experience. Although we try to make the installation process as easy as possible, gear tuning experience as well as some customizations are still required."
Last edited by smallwheeler; 05-12-14 at 11:44 AM.
#20
Banned
Just normal tempered steel cogs would be fine To My Pragmatic mind .. rather than Titanium ..
but Bike bling /weight weenieists are more willing to put the $350 out for Ti.
Back in the late 50's early 60's I added a steel 3 cog cluster to my AW3, English, Cyclo It think..
it was 1 piece of steel machined with all 3 cogs in 1 chunk, slid right on in place of the 1 1/8" cog & 2 spacers ..
No instructions to not use a wide chain in a derailleur set up back then, so I did .
fitted a steel triple crank too .. 3x3x3 a 27 speed . 3 shift levers .
but Bike bling /weight weenieists are more willing to put the $350 out for Ti.
Back in the late 50's early 60's I added a steel 3 cog cluster to my AW3, English, Cyclo It think..
it was 1 piece of steel machined with all 3 cogs in 1 chunk, slid right on in place of the 1 1/8" cog & 2 spacers ..
No instructions to not use a wide chain in a derailleur set up back then, so I did .
fitted a steel triple crank too .. 3x3x3 a 27 speed . 3 shift levers .
Last edited by fietsbob; 06-14-15 at 12:30 PM.
#21
DancesWithSUVs
Join Date: Apr 2005
Location: Griffin Cycle Bethesda,MD
Posts: 6,983
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Likes: 0
Liked 2 Times
in
2 Posts
Word from the bike shop is that parts for the job comes to $363. That plus labor means the cost of conversion will push $600. So it looks like I'm looking at another Brompton.
On the other hand, the three speed is good enough, quite nice even, for 90%+ of the riding I do
On the other hand, the three speed is good enough, quite nice even, for 90%+ of the riding I do
Free Shipping 16 x1 3 8" 349 Light Weight Silver 5 Speed Rear Wheel Brompton | eBay
Parts swap is something you could do yourself,you'd just want to hit up a local co-op/bike kitchen to get the wheel properly tensioned first. You'd also still have your stock 3spd setup,which you could put on eBay/CL and sell to bring the cost down further.
__________________
C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L/S2E-X
C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Dahon Speed Pro TT,Brompton S6L/S2E-X
#22
Banned
FWIW Brompton Uses a much heavier spoke on the rear, to stand up to a commuter beating , 14 gage would be the light gage they use on the front.
#23
Senior Member
Thread Starter
Join Date: Aug 2012
Location: The Big City
Posts: 619
Bikes: Brompton M3L, Tern Verge P20, Citi Bike
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 85 Post(s)
Likes: 0
Liked 9 Times
in
7 Posts
Might want to look into a 5 speed:
Free Shipping 16 x1 3 8" 349 Light Weight Silver 5 Speed Rear Wheel Brompton | eBay
Parts swap is something you could do yourself,you'd just want to hit up a local co-op/bike kitchen to get the wheel properly tensioned first. You'd also still have your stock 3spd setup,which you could put on eBay/CL and sell to bring the cost down further.
Free Shipping 16 x1 3 8" 349 Light Weight Silver 5 Speed Rear Wheel Brompton | eBay
Parts swap is something you could do yourself,you'd just want to hit up a local co-op/bike kitchen to get the wheel properly tensioned first. You'd also still have your stock 3spd setup,which you could put on eBay/CL and sell to bring the cost down further.
#24
Part-time epistemologist
The start of bike-itis. Find a way to fit two bikes in that closet!
__________________
A narrative on bicycle driving.
A narrative on bicycle driving.
#25
Banned
The 2/single speed 1 or 2 cog hub is already a weight choice, so I suppose the derailleur 3rd cog follows on that line..
suppose next they have to create a way to use the rightLever, for the IGH detents indexing the pulley pusher.
since the either or left shifter doesn't need a 3rd positon..
I think the 349 'kojak' is a 32 .. and the 5 speed hub is in 28 spoke, and same hub shell diameter to use the stock Brompton rim and spoke.
just that vendor aimed at the customer wanting the racier options.
suppose next they have to create a way to use the rightLever, for the IGH detents indexing the pulley pusher.
since the either or left shifter doesn't need a 3rd positon..
I think the 349 'kojak' is a 32 .. and the 5 speed hub is in 28 spoke, and same hub shell diameter to use the stock Brompton rim and spoke.
just that vendor aimed at the customer wanting the racier options.