# Brompton gearing



## The Eco Worrier (23 Jul 2014)

I have a 3 speed Brompton, I understand they can be converted to 3+ by messing with the gearing ratio. Does anyone know how to do this?

Thanks


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## T4tomo (23 Jul 2014)

You can retro fit the derailleur to convert to a six speed, but to be honest I wouldn't bother as the change is then fiddly for sequential gearing.

alternatively, if you thinnk you neeed highr or lower gears then you can change the chainring and or sprocket size.


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## jay clock (23 Jul 2014)

I changed the front ring for 46T on my S3L - means I am able to cycle up hills spinning nice and fast, and use 2/sometimes 3 on the flat. Steeper downhills I coast. Suits me perfectly


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## The Eco Worrier (23 Jul 2014)

Adrian,I can see form the order form they are now calling it raised gearing





So 3 speed with raised gearing as opposed to 6 speed.

Jay, I think by changing to 46t I would have a lowered gearing which is not what I am after.


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## jay clock (23 Jul 2014)

@The Eco Worrier yes you are right, but that is what i wanted.! I tend to spin like a dervish and although I do not have many steep hills to climb I use the first gear daily


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## CopperBrompton (23 Jul 2014)

Yes, you can fit a bigger or smaller chainring to raise or lower the gearing. There are three standard ring sizes approved by Brompton.


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## rualexander (24 Jul 2014)

Trikeman said:


> Yes, you can fit a bigger or smaller chainring to raise or lower the gearing. There are three standard ring sizes approved by Brompton.


Or you can use any size chainring you like if it fits the chainset, or change the chainset and fit smaller still rings or fit a double chainring to give two ranges and move the chain between rings by hand.


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## The Eco Worrier (24 Jul 2014)

rualexander said:


> Or you can use any size chainring you like if it fits the chainset, or change the chainset and fit smaller still rings or fit a double chainring to give two ranges and move the chain between rings by hand.



I like the idea of a stop and rest between gear changes, especially on the hills!!

I have a 50T front chainring and 13T rear, so it looks like I can up the front one a bit.

Thanks all!


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## jay clock (24 Jul 2014)

If you email Brompton via their tech support website they are very good


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## T4tomo (28 Jul 2014)

The Eco Worrier said:


> I like the idea of a stop and rest between gear changes, especially on the hills!!
> 
> I have a 50T front chainring and 13T rear, so it looks like I can up the front one a bit.
> 
> Thanks all!


Yes you can go upto a 54T which is what I used to run before I moved to a hillier area and switched to 50-13.


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## Crankarm (29 Jul 2014)

T4tomo said:


> You can retro fit the derailleur to convert to a six speed, but to be honest I wouldn't bother as *the change is then fiddly for sequential gearing.*
> 
> alternatively, if you thinnk you neeed highr or lower gears then you can change the chainring and or sprocket size.



Not in my experience.


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## TheDoctor (5 Aug 2014)

^^This. I don't find the gearchange fiddly at all on my 6 speed Brommie.
Having said that, I could swap out the 50T chainring for a 40T, losing the 99" top gear and gaining a 22", which would be more useful to me. I haven't, as that means the change between my two most-often used gears would be a double change, and I'd sooner not do that every few minutes.
But the gearchange isn't an issue in everyday use.


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## GrumpyGregry (5 Aug 2014)

Yes, the Brompton six speed gear shift is such an awesome solution many of us are completely baffled why every other manufacturer has not adopted it.


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## TheDoctor (14 Aug 2014)

I know - having *two* gear levers is a stupid idea. It'll never catch on!


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## sreten (18 Aug 2014)

GrumpyGregry said:


> Yes, the Brompton six speed gear shift is such an awesome solution many of us are completely baffled why every other manufacturer has not adopted it.



Hi,

Because a 2 speed derailleur and 3 speed hub makes no cost sense compared to a 6 speed derailleur,

rgds, sreten.


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## Rohloff_Brompton_Rider (18 Aug 2014)

GrumpyGregry said:


> Yes, the Brompton six speed gear shift is such an awesome solution many of us are completely baffled why every other manufacturer has not adopted it.


Apart from very few IGH's , name a set up with the same gear range of the 6 speed Brompton that doesn't use two levers.


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## GrumpyGregry (18 Aug 2014)

bromptonfb said:


> *Apart from very few IGH'*s , name a set up with the same gear range of the 6 speed Brompton that doesn't use two levers.


As phrased it is a ridiculous question.

I love my Brompton but I'm not blinded to the faults in their approach.


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## Rohloff_Brompton_Rider (18 Aug 2014)

GrumpyGregry said:


> As phrased it is a ridiculous question.
> 
> I love my Brompton but I'm not blinded to the faults in their approach.


What the fark you on about? It's an easy question, just answer it.


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## msubikes (23 Jun 2022)

We've got a customer with a 3 speed internal x 2-speed freewheel/ cassette that needs a new chain and cogs. I've read that the cogs are standard Shimano type cassette cogs and also that they are something special perhaps made just for Brompton? Can anyone confirm what they are? We're in the USA and want to make sure we've got the right parts on hand to replace them for the customer as it's his primary transportation. He's also needing a new left shifter cable/housing. Is that a standard shift/cable & housing or something special for these Bromptons? Unfortunately the bike is no longer here in our shop.


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## T4tomo (23 Jun 2022)

msubikes said:


> We've got a customer with a 3 speed internal x 2-speed freewheel/ cassette that needs a new chain and cogs. I've read that the cogs are standard Shimano type cassette cogs and also that they are something special perhaps made just for Brompton? Can anyone confirm what they are? We're in the USA and want to make sure we've got the right parts on hand to replace them for the customer as it's his primary transportation. He's also needing a new left shifter cable/housing. Is that a standard shift/cable & housing or something special for these Bromptons? Unfortunately the bike is no longer here in our shop.



Is the customers bike a Brompton? - i think yes.

you need the correct sprockets to match the Hub gear fitted, which may be SA or SRAM. They are defo not standard shimano cogs, wipe that thought from your mind. 3/32 size chain needed and the SA / SRAM sprockets to match

shifters are Brompton specific as is the rear "derailleur" shifter


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## msubikes (23 Jun 2022)

T4tomo said:


> Is the customers bike a Brompton? - i think yes.
> 
> you need the correct sprockets to match the Hub gear fitted, which may be SA or SRAM. They are defo not standard shimano cogs, wipe that thought from your mind. 3/32 size chain needed and the SA / SRAM sprockets to match
> 
> shifters are Brompton specific as is the rear "derailleur" shifter



Sorry, yes, it's a Brompton. Thank you for clarifying that these sprockets are NOT Shimano-type cogs and the shift cables/housing are also unique (as I suspected). We'll keep hunting for the correct parts. I've got an email in to Brompton support for help.


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## Tenkaykev (23 Jun 2022)

msubikes said:


> We've got a customer with a 3 speed internal x 2-speed freewheel/ cassette that needs a new chain and cogs. I've read that the cogs are standard Shimano type cassette cogs and also that they are something special perhaps made just for Brompton? Can anyone confirm what they are? We're in the USA and want to make sure we've got the right parts on hand to replace them for the customer as it's his primary transportation. He's also needing a new left shifter cable/housing. Is that a standard shift/cable & housing or something special for these Bromptons? Unfortunately the bike is no longer here in our shop.



Take a look at the excellent Brilliant Bikes YouTube channel, there are lots of really useful and informative videos on there including some gearing specific ones.


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## Schwinnsta (23 Jun 2022)

Shimano spline 2mm


msubikes said:


> We've got a customer with a 3 speed internal x 2-speed freewheel/ cassette that needs a new chain and cogs. I've read that the cogs are standard Shimano type cassette cogs and also that they are something special perhaps made just for Brompton? Can anyone confirm what they are? We're in the USA and want to make sure we've got the right parts on hand to replace them for the customer as it's his primary transportation. He's also needing a new left shifter cable/housing. Is that a standard shift/cable & housing or something special for these Bromptons? Unfortunately the bike is no longer here in our shop.


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## berlinonaut (23 Jun 2022)

msubikes said:


> We've got a customer with a 3 speed internal x 2-speed freewheel/ cassette that needs a new chain and cogs. I've read that the cogs are standard Shimano type cassette cogs and also that they are something special perhaps made just for Brompton? Can anyone confirm what they are? We're in the USA and want to make sure we've got the right parts on hand to replace them for the customer as it's his primary transportation. He's also needing a new left shifter cable/housing. Is that a standard shift/cable & housing or something special for these Bromptons? Unfortunately the bike is no longer here in our shop.


as often: It depends. It it is a newer bike (after 2009) the cogs on the 6-speed S/A hub are shimano-compatible. If it is older they are not as those use an SRAM hub. While you could use Shimano cogs on the newer bike as a customer I would usually expect the correct factory parts. Bromton does have a US distribution and getting the cogs from them should be no big deal and you can be sure that they fit w/o tinkering. 
Same goes for the shifters: Cable length is very critical as is cable routing. The correct type of cables depends if the bike was made before or after 2017. Brompton do sell the correct cables for both models in the correct length for the different handle bars. So while it is no big deal to use 3rd party parts the devil is in the detail and if you don't have experience with the Brompton chances are high that you will mess something up w/o recognizing it.
The chain is no issue. Any 8 or 9 speed will do.


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## u_i (24 Jun 2022)

If this is your website, I am normally located minutes from you and may be able to help. At this moment I am away, though, and will be back only next week. There is a number of Brompton dealers now in the US, a big shift compared to decade ago when they were just two, and even REI now carries Brompton. For parts I would suggest Perennial Cycle, Clever Cycles, Curbside Cycles (Toronto but little time/price penalty f/over border), J. C. Lind Bike. Co. (Chicago) and Universal Cycles. Brompton shift cables use unusual nipples and uncommon ferrules for housing - I would not try to make the standard cables work in a rudimentary service.


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## berlinonaut (24 Jun 2022)

u_i said:


> If this is your website,



A bike repair center run by a university! THAT is awesome!


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## u_i (24 Jun 2022)

berlinonaut said:


> A bike repair center run by a university! THAT is awesome!



While even their existence impacts the local culture, they also undertake various conscious social efforts. Thus, e.g., every year hundreds of bikes get abandoned over the campus by students and longer-term visitors departing the university. Police collect those bikes and the Bike Shop fixes them and offers them at a low price to the incoming students and visitors.


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## FLYINGGATER (27 Jul 2022)

sreten said:


> Hi,
> 
> Because a 2 speed derailleur and 3 speed hub makes no cost sense compared to a 6 speed derailleur,
> 
> rgds, sreten.



Quite common pre WW2 some hubs had 3 sprockets


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