# Brompton 3 or 6 gears



## Rebelsurfer (5 Aug 2019)

Hi Fellow folding bike people!

I am about to make the plunge and buy a Brompton. I would like to pootle around London and maybe venture further afield. The big question (well it is for me) should I buy a 3 speed or a 6?? I'm a newbie, so be kind... Looking forward to parting with my cash for a new or second-hand Brompton. Hoping to meet up with other Brompton owners for days out !


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## Tenkaykev (5 Aug 2019)

Six is more versatile for only a little extra weight over the three. 
It’s better to have six available and not need to use them than to need them and not have them. 

Bromptons are great fun and very versatile, I'm sure you'll love yours, but if it proves not to be for you then you can always sell it without losing a lot of money.


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## ianrauk (5 Aug 2019)

Unless you are doing lots of hills and/or touring then I would go for the 3 gear option. 
I commuted in London for a while with a 6 speed version. It was 3 more gears then I really needed.
The other main problem with the 6 gear option is that if you are using the bike in all weathers then the derailleur has to be cleaned after every rainy or mucky ride. You fail to clean it and the shifting will become troublesome in a very short time.


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## Ming the Merciless (5 Aug 2019)

I have a three speed and it's been up a few alpine cols amongst other outings. Just need to get out the saddle a bit more for steeper gradients. Otherwise fairly maintenance free.


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## mitchibob (6 Aug 2019)

If you're only riding around London, the 2-speed is the best option. Apparently, it's pretty good for the Ride London 100 too, although I'm not that hardcore. But it's a lot lighter and more efficient.

However, between the 3 and the 6 though, I'd go for the 6 if you really are planning on going further afield as it's just that little wider choice of gears with the ratios a little closer together, and it's not much extra weight. I'm also finding that the 54T chainring on the 6-speed to be ideal around town, but also for the Ride 100. 5hrs 59mins 47seconds on Sunday... used every gear.


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## JulesBlue (7 Aug 2019)

I have a six speed, but I only seem to use the first three, the rest are way too hard, and I cycle most of the time, so my legs are pretty used to it. Having said that, I don't know if the ratio of the first three of a six speed differ to the ratio of a three speed only bike.


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## TheDoctor (7 Aug 2019)

I've always been of the opinion that if there's any chance at all of needed the 6 speed, then get it.
While you can convert a 3 speed to 6, it's bloody expensive and needs a new back wheel.
For touring and hills - just get the 6.
Having said that, some people just don't get on with the double shifts of the 6 speed.
Any chance you could have a test ride before deciding?
FYI, the gear inches of the various gearing options are as follows.
6 speed 33 41 52 64 81 100
3 speed 48 64 84
2 speed 56 74

I can vouch that the lowest gear of the 6 speed will get you (and touring kit) up a steep hill at just-above walking speed, and the highest gear will get you going far faster downhill than feels sensible. Or fun.
Lowest gear on a 3 speed is not low enough IMHO.
2 speed is just silly unless you're somewhere really flat. Again, IMHO.


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## alicat (8 Aug 2019)

JulesBlue said:


> I have a six speed, but I only seem to use the first three, the rest are way too hard, and I cycle most of the time, so my legs are pretty used to it. Having said that, I don't know if the ratio of the first three of a six speed differ to the ratio of a three speed only bike.



It's possible to lower the overall gearing by fitting a smaller chainring at the front or bigger sprockets at the back. That's what I did and now I use all six gears.


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## Tenkaykev (8 Aug 2019)

Wot Alicat said ^^^

I swapped to a 44 tooth ring on my and my wife's Bromptons, it's a tad hilly around Dorset. Now I find I can make the last 50 metres to the pub without having to get off and push

Top gear is plenty fast for me, I even managed several laps of Saturday's Brommie race without disgracing myself.


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## berlinonaut (8 Aug 2019)

Dogtrousers said:


> Seems like everyone is recommending what they have. So I will too.



Hmm, I have all three.  I'd recommend either the two speed or the six speed with the smaller chain wheel (44t). Two speed for simplicity, fun and weight - it is able to deliver way more than one would expect and ist in no way "just silly". Six speed offers a wider range but is way too long in factory mode. Thus 44t chainwheel. To get rid of the relatively huge gear steps I converted mine to a nine speed with 3 sprockets in the back. Still dealing with the two shifters is a bit annoying though one get's used to it after a short while. Cannot imagine to run the six-speed with a 54t chainwheel - I consider this to be far to long.
The three speed has the weight and the drag caused by the hub of the six speed, but offers nothing relevant in addition to the two speed, it basically combines the downsides of six-speed and two speed with no upsides. Weight and drag of the six speed, limited range and huge gear step(s) of the two speed. Too long for steeper hills and - worse - the third is considered too long by most people even in the flat where the 2nd speed is too short. 179% spread of the three speed are in practice not much more useful than the 133% of the two-speed (if at all - I consider it in fact LESS useful). A sprocket with one or two teeth more is helpful but the other limitations still apply. So I'd avoid the three speed and go for the two speed for commuting and touring in flatter areas. For wider touring or hilly areas go for the six-speed with 44t chainwheel.


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## T4tomo (8 Aug 2019)

JulesBlue said:


> I have a six speed, but I only seem to use the first three, the rest are way too hard, and I cycle most of the time, so my legs are pretty used to it. Having said that, I don't know if the ratio of the first three of a six speed differ to the ratio of a three speed only bike.


Your chainring is too big then


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## TheDoctor (8 Aug 2019)

@berlinonaut I meant the two speed standard gearing is just silly. The -19% option would be perfect for me in not -very -hilly Stevenage.


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## berlinonaut (8 Aug 2019)

TheDoctor said:


> @berlinonaut I meant the two speed standard gearing is just silly. The -19% option would be perfect for me in not -very -hilly Stevenage.



I run the 2-speed with a 60t chainring, mainly in mostly flat Berlin but also everywhere else (but not on a daily basis). For my taste the stock 54t delivers a very good compromise that should fit most riders but obviously this highly depends from your fitness, your preferred cadence, your preferred speed and also the terrain that you are riding. For me the -19% on the two-speed would be as silly as my 60t chainwheel would probably be for you.


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## TheDoctor (8 Aug 2019)

*envies*
I liked cycling round Berlin, even if it was just for a few hours on a borrowed fixed.
I think we're all busily proving @Dogtrousers right! The OP really needs to try a few and see what suits...


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## 12boy (8 Aug 2019)

Here's my 2 cents. This setup is easy and cheap and much lighter than the IGH option. 58 and 38 tooth chain rings up front and 12 and 17 sprockets on the rear. This yields 78 and 51 gear inches on the big chain ring and 55 and 36 on the little. I can climb the hills in my area fairly well on the 38 and cruise along on level to slightly rising or with headwinds on the 58. Downsides are it doesn't fold well with the 38 so I fold on the 58. I shift with the greasy finger method but unless it steep and long I don't bother. I may try a 18 tooth sprocket which would yield a low of 34 gear inches, but I am not sure if that difference is really noticeable. If my rides involved a lot of cargo weight I would have to go lower on climbs.


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## T4tomo (8 Aug 2019)

Unless you aren't doing any hills at all the 2spd is quite limited (but a good option for a flat town commute) which is why Berlinonaut is recommending it I guess.

3 spd is most robust for minimal maintenence, As the 2spd and 6spd rely on the rear derailleur, which as mentioned further up thread, can be temperamental if not kept clean.

I Have had several years on 3 spd standard and then several on 3spd - 12%, I favour the latter. Better to run out of gears at the top end than the bottom. You won't use 1st in London on either set up though!


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## Ming the Merciless (8 Aug 2019)

I have a three speed and have got used to riding out if saddle when steep stuff turns up. Keeps you fit and is good fun.


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## oldwheels (9 Aug 2019)

I use a 6 speed with a 40 tooth chainring and use all 6 gears. On the flat I spin out at about 18 mph in top but that was only for test purposes and never get near that speed in everyday use.


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## TheDoctor (9 Aug 2019)

I think I've twice had to get the rear mech off and take it to bits.
For context, I've had the bike about a decade, and worn the transmission out in that time. And I'm toying with the idea of replacing the Marathon tyres after a mere seven years.


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## kais01 (9 Aug 2019)

2 or 6. i really fail to see why accepting the weight penalty of a hub, and not keeping the derailer with almost no weight penalty at all.

but.

the 2x3 bwr have too big steps for a multigeared bike. really!!

so the option i highly recommend newcomers is buying a bsr 3-speed and have the shop add the 2-speed derailer kit with 13 + 15 cogs, thereafter pick chainring according to taste and leg strength. get 6 reasonably close-ratio gears. much better than the bwr out on open road.

of course for the technically skilled all kinds of other options are open. in our family we have 2sp with a 50t for my wife, with 69t for me, a 5sp with 305/44 tyres for winter, a 2x5 oldie with 13+14 cogs giving really close ratios, and my 2x10 dura-ace/schlumph with about 14 unique super close ratio gears about the same as a tdf racer.

but the 2x3 bsr is a good start for anyone.


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## berlinonaut (10 Aug 2019)

kais01 said:


> so the option i highly recommend newcomers is buying a bsr 3-speed and have the shop add the 2-speed derailer kit with 13 + 15 cogs, thereafter pick chainring according to taste and leg strength. get 6 reasonably close-ratio gears. much better than the bwr out on open road.



There's a simple and very good reason why one would not do that: It does not work. The derailleur upgrade from a 3-speed only works with the SRAM Hubs that were replaced with the SRF-3 (later renamed to BSR) already back in 2005 - 15 years ago. It does NOT work with the BSR. You can however modify a 3-speed BSR-hub by using parts of the BWR and adding the freewheel parts of this hub to the BSR and thus making it able to deal with 2 sprockets and the derailleur, but this is a rarely made modification, nothing for total beginners and finding out which parts one exactly needs, then getting hold of those parts and finally putting the things together appropriately and may be a bit of a showstopper for most people. The more as the gain in spread from the 3-speed is just from 178% to 214% - not too impressive and probably only for very few people not worth the hassle.
My modification of the BWR to 9-speed ist way easier and cheaper and adds spread as well as small gear-steps to the BWR. However: For most people this would possibly be overengineering, too.



kais01 said:


> but the 2x3 bsr is a good start for anyone.



I don't think so, for the reasons outlined above. And furthermore I always have my doubts when someone says something would be "_good for anyone"_. People are different as are their needs and desires and in most cases the person giving such advice just thinks what he considers to be good for himself must be good for anyone, thus showing a bit of a limited imagination and overestimating himself...


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## kais01 (10 Aug 2019)

sorry berlinonaut, exchanging cogs in the 2x3 kit is hardly expert work...

making the 3speed derailer is, as you are likely to be aware of. fiddly is its middle name


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## berlinonaut (10 Aug 2019)

kais01 said:


> sorry berlinonaut, exchanging cogs in the 2x3 kit is hardly expert work...



Exchanging cogs is definitively not hard work. Making two cogs fit onto a BSR hub is. Because without that the 2*3 obviously does not work and the BSR is not prepared to take two cogs from the factory. Did you do it? Or do you confuse it with the former SRAM hub (which could easily be upgraded from 3 to 2*3 spreed but is - as I wrote - gone for a very long time already). If you know an out-of-the-box way of upgrading the BSR I would love to learn about it!


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## kais01 (10 Aug 2019)

well as far as i know the bsr has the same 3 tagged fastening originally meant for a single cog as the torpedo/sachs/sram. but the kit works regardless, because the cogs in the kit are narrower, and if i remember correctly the fastening spring is also slightly narrower.

i recommend this setup for the novice because they dont have to anything themselves. the conversion can be performed by any authorised brompton workshop. there is a ready-made all inclusive kit sold by brompton. even the chain is in the package

the 3sp derailer is off limits there, and better suited for you and me

have made this conversion on at least three brommies and still have one or two kits in my garage.


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## berlinonaut (10 Aug 2019)

kais01 said:


> well as far as i know the bsr has the same 3 tagged fastening originally meant for a single cog as the torpedo/sachs/sram.



It uses the same style of sprockes (with three "noses") but as far as I know the conversion to two sprockets still does not work on the BSR (it did on some of the Sprinter hubs). Would be good to know if it is different.



kais01 said:


> but the kit works regardless, because the cogs in the kit are narrower, and if i remember correctly the fastening spring is also slightly narrower.
> (...)
> I have made this conversion on at least three brommies and still have one or two kits in my garage.



So we talking about part number
QDRRETSET3SR->6SR as outlined here?
*UPGRADEKIT SRAM-3V NAAR SRAM-6V *
http://www.vlerickfietsen.be/brompton/spareparts/versnelling_buiten/upgradekits/index.html

So did you really apply this conversion *to a BSR hub* or do you just believe that it will fit due to the sprockets having the same shape and have only applied it to Sram hubs?


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## kais01 (10 Aug 2019)

i just believed

if someone says it does not work that is something we both have heard in in the past. if you have specific info of why it most surpricingly would not work it really would be nice to know

ot; in a somewhat related example i heard something similar from expert mechanics when back in the days i wanted to add a third cog to the torpedo/sram hub. went without any problems on with that anyway, and later did not stop until i reached six.

later came similar hybrids on the market.


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## kais01 (10 Aug 2019)

so here are the two hubs in question...


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## berlinonaut (10 Aug 2019)

I am not very interested in this mod anyway but I still have a Brompton SRF-3 rear wheel collecting dust in my workshop but unfortunately no SRAM 6-speed. So if I do not forget it I might just order a sprocket set for the Sram 6-speed the next time I need parts and try it out for the sake of science.  Should not be too expensive, just not sure if those sprockets are still available as a Kit from Brompton - looks as if they were discontinued.


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## kais01 (10 Aug 2019)

you should be ok. my guess you need to keep the bsr fascia, and maybe this is what any compatibility issue is about.

of course to make the conversion you, or our ts does not need the kit, the friendly brompton store is likely to have the necessary parts on hand, for example when buying a bike. 

my experience is they change out freely on new bikes after customer's demand.


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## u_i (11 Aug 2019)

So to understand, one speed-doubling BSR conversion goes through adopting hardware from BWR that then allows mounting Shimano cassette cogs. The more straightforward conversion utilizes cogs that directly fit BSR. Would the latter cogs basically be 3-spline Sturmey-Archer cogs widely available from different vendors?


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## berlinonaut (11 Aug 2019)

Updated information: I got hold of the spec. of the sprockets and smaller parts for the various hubs via a Brompton technical data sheet. Looks like that (inner to outer):

*SRAM 3-speed*
0,85mm dust cap
2,2mm spacer
3,0 or 3,1mm sprocket
2,2mm spacer
circlip (to hold the parts in place)
________________________________
total 8,05 - 8,15mm

*SRAM 6-speed*
0,85mm dust cap
2,0mm 15t sprocket
2,2mm spacer
3,0mm 13t sprocket
circlip
________________________________
total 8,05mm

*S/A 3-speed (Alloy shell -> SRF-3/BSR)*, not applicable for the older steel shell 3-AW
2,1mm dust cap
no spacer
3,0 or 3,1mm sprocket
no spacer
circlip
________________________________
total 5,1-5,2mm

The circlip (QRSPRCLIP) is identical for all hubs as is the 13t sprocket (QSPR13DR) for SRAM and S/A-3-speed (not BWR hubs). The 3-speed versions can however take a couple of different 13t or 14t sprockets as well (all being 3,0 or 3,1mm of width), on the SRAM 6-speed it has to be the 3,0mm wide part number QSPR13DR (which has a flange that has to be mounted inwards on the 6-speed) . The 15t on the SRAM 6-speed (QSPR15DR) has an arrow that has to face outwards.

I measured the available space on a 2008 SRF-3 (BSR) hub and ended up with shortly below 5mm of space on the driver from the inner limit to the beginning of the notch that the circlip sits in.

So the BSR runs short by 3mm and even if one would omit the dustcap (assuming that this would work) one would still run 2mm short. So with the stock conversion parts/sprockets intended for the SRAM hub it defitively does not work to convert the SRF-3/BSR to two sprockets. A very comitted worker could maybe try to slim down the 13t sprocket from 3,0mm to 2,0mm and try to use a massively slimmer circlip (along with omitting the dustcap). Maybe two sprockets would physically fit - don't know. A lot of tinkering anyway. If it would not only physically fit but also work I cannot tell.

Obviously the SRAM offers - as assumed - way more space on the driver than the BSR, thus a straightforward, simple conversion is not possible and I doubt that the tinkering way would work flawlessy (but love to be proven wrong). If - for whatever reason - you want six speeds of a BSR swapping to the driver of the BWR along with some other parts seems the way to go (which offers the convenience of a far wider range of sprocket-sizes to choose from as well as way easier possiblities to get hold of those). Alternatively go for a used SRAM wheel - the are typically not very expensive.


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## kais01 (13 Aug 2019)

thanks for the thourough walkthrough berlinonaut. but writing that was most definitely a bigger effort than making the conversion work regardless

key seems to be to use a thinner dustcap and grind the cirklip narrower on the side which supports the cogs, something i have performed a number of times. takes about two minutes.

when i get home from vacation in a few days i will check the dimensions in the kit.


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## chriscross1966 (19 Aug 2019)

I've got a SRAM 6-speed wheel that id be happy to sell... should have some spare sockets for it too


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## CSG (26 Aug 2019)

I don't know a thing about the new models but when I bought my M6L in 2011, and living in Idaho, getting the six-speed (three really with a low and high option) with the 12% reduction made great sense. I'm not a heavy user of the bike but it rides in the back of my Land Cruiser under the philosophy of "always have a bike". It's been trouble free for eight years so far and running on the original Brompton Kevlar tires.

I almost never use the lowest gears but they are there when I need them.


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## Handlebar Moustache (28 Aug 2019)

In Edinburgh the 6-speed with reduction is fab and well worth it. You can also get on the straights up to 20mph without totally spinning out so it’s very useful.


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## Kell (3 Sep 2019)

Handlebar Moustache said:


> In Edinburgh the 6-speed with reduction is fab and well worth it. You can also get on the straights up to 20mph without totally spinning out so it’s very useful.



I bought the reduced chainring last time I swapped it out - as a trial run to help my knees on the climb out of my train station.

But, IMHO, it's compromised the speed of the bike too much elsewhere. 22mph is now where I top out (I prefer a lower cadence) and rather than being just low enough to bring each additional higher gear into play on my usual stretches (i.e. being able to use 5th where I would normally use 4th), it's effectively cut a couple of mph off every other stage of my commute as I'm still using the same gears, pedalling at a similar rpm and therefore going slower.

Next time I order a new chainring, I'll be going back to the 50T and just have to lump it on the hill.


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## Ming the Merciless (3 Sep 2019)

CSG said:


> I don't know a thing about the new models but when I bought my M6L in 2011, and living in Idaho, getting the six-speed (three really with a low and high option) with the 12% reduction made great sense. I'm not a heavy user of the bike but it rides in the back of my Land Cruiser under the philosophy of "always have a bike". It's been trouble free for eight years so far and running on the original Brompton Kevlar tires.
> 
> I almost never use the lowest gears but they are there when I need them.



I have the philosphy of "always ride a bike". Can't you fit the land cruiser in the front brompton bag in case of problems?


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## Handlebar Moustache (3 Sep 2019)

Kell said:


> I bought the reduced chainring last time I swapped it out - as a trial run to help my knees on the climb out of my train station.
> 
> But, IMHO, it's compromised the speed of the bike too much elsewhere. 22mph is now where I top out (I prefer a lower cadence) and rather than being just low enough to bring each additional higher gear into play on my usual stretches (i.e. being able to use 5th where I would normally use 4th), it's effectively cut a couple of mph off every other stage of my commute as I'm still using the same gears, pedalling at a similar rpm and therefore going slower.
> 
> Next time I order a new chainring, I'll be going back to the 50T and just have to lump it on the hill.



Fair enough - our mileage may differ ;-)


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## Tenkaykev (3 Sep 2019)

Handlebar Moustache said:


> In Edinburgh the 6-speed with reduction is fab and well worth it. You can also get on the straights up to 20mph without totally spinning out so it’s very useful.



I just copied and pasted your post into a message to our daughter who lives in Porty. 
She's just got a 6 speed Brompton after having a trial ride on mine whilst visiting a few weeks ago. 

I've offered to take a 44 up with me when we visit later this month.


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## Handlebar Moustache (3 Sep 2019)

Tenkaykev said:


> I just copied and pasted your post into a message to our daughter who lives in Porty.
> She's just got a 6 speed Brompton after having a trial ride on mine whilst visiting a few weeks ago.
> 
> I've offered to take a 44 up with me when we visit later this month.



I’m not the fastest but I am always confident of going anywhere on my B - even up Dundas / Victoria Street


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## 12boy (3 Sep 2019)

For quite a while I have gone with a 4 speed......58 and 38 tooth chain rings and 12 and 17 sprockets. Pretty good most of the time but steep grades plus a 15 mph headwind was taxing. Since I am using a 118 mm Shimano BB and a 110 BCD crank arm it was easy to add a 24 tooth chain ring which I will test further today. These chain rings require manual shifting which requires stopping but only takes 10 seconds, and the bottom two are rarely used. The 58/17 combo is good for 5% grades of a 1/2 mile or less. This set up weighs much less than a 3 speed IGH but doesn't provide a higher gear than 77 gear inches. Still, it is a simple, clean set up that is cheap and easy. A 58/38 chain ring can also be done easily with the 130 BCD crank that comes with newer Brompton, but I don't think less than 38 is available. So, Kell, add a chain ring if you want to keep your high and low options. From your video clip of going to work at at 40 plus mph, you could go with the 50 to work and switch to the smaller to go home. That assumes the ride in is mostly downhill.

Since wrting this earlier I did discoverer that it rode fine but the 24 tooth chainring hit the mainstay when folding so I took it off. I can replace the 17 tooth sprocket with an 18 and replace the 38 tooth chain ring with a 34 but I may wait a while on that although it gets me to about 30 gear inches which might be a little better.


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## berlinonaut (3 Sep 2019)

Kell said:


> I bought the reduced chainring last time I swapped it out - as a trial run to help my knees on the climb out of my train station.
> 
> But, IMHO, it's compromised the speed of the bike too much elsewhere. 22mph is now where I top out (I prefer a lower cadence) and rather than being just low enough to bring each additional higher gear into play on my usual stretches (i.e. being able to use 5th where I would normally use 4th), it's effectively cut a couple of mph off every other stage of my commute as I'm still using the same gears, pedalling at a similar rpm and therefore going slower.
> 
> Next time I order a new chainring, I'll be going back to the 50T and just have to lump it on the hill.



If you spin out at 22 mph with a 44t chainring and a BWR with stock 13t/16t this equals a cadence of ~83 while 22 mph equal about 35 kph according to ritzelrechner. Both pretty impressive in my opinion. I do not reach cadence of more than 80 for more than a short distance most of the time (in the flat) and consider around or slightly above 75 to be my favorite. I would personally not consider 35 kph to slow on a Brompton - my usual travel speed is around 28 kph with the 2-speed with 60/12-16. I run my BWR with the 44t chainwheel but considered this too low as well - this was one of the reasons to modify it to 44/12-14-16. Way better for my taste, offering sufficient speed in the flat and sufficient hill abilities at the same time. Still a tad shorter than the 50t chainwheel (which I consider to be too long anyway) but with a much wider spread and longer than the stock 44t.


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## Kell (4 Sep 2019)

I must admit, I hardly used 6th on the 50T chainwheel, but I did use it. 

83 does sound a little low, but I've not done the maths (and wouldn't have known where to start), but I do find it harder to spin quickly on a Brompton as opposed to my road bike. I've got a couple of those Sufferfest videos I use on the Turbo Trainer and at times you're spinning at 110RPM, which I feel would be almost impossible on the Brompton. Maybe it's the shorter cranks, or the position you're in on the bike.

I did look down this morning as I was descending a very steep hill and noticed that it was about 25 mph when it felt unsafe and I couldn't keep up - certainly not with the 44mph top speed that I get down there.


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## Kell (4 Sep 2019)

Tell a lie, this morning it was 47mph.


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## Tenkaykev (4 Sep 2019)

Kell said:


> Tell a lie, this morning it was 47mph.
> 
> View attachment 483418



Looking at the elevation graph I have a mental image of you whizzing off the short incline like a Ski jumper ⛷️


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## Dogtrousers (4 Sep 2019)

Tenkaykev said:


> Looking at the elevation graph I have a mental image of you whizzing off the short incline like a Ski jumper ⛷️


Like this?


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## Kell (4 Sep 2019)

It is pretty steep.


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## berlinonaut (5 Sep 2019)

Kell said:


> 83 does sound a little low, but I've not done the maths (and wouldn't have known where to start)



Just klick on the links in my last post.



Kell said:


> I did look down this morning as I was descending a very steep hill and noticed that it was about 25 mph when it felt unsafe and I couldn't keep up - certainly not with the 44mph top speed that I get down there.



My top speed with a Brommi on a descent was somewhat north of 70kph (the person behind my had a speedometer and stopped keeping up with me at 68kph as he considered it to be too frightening while I was accelerating further). I did not feel unsafe in any way and neither did the bike. Obviously if anything unforeseen happens at that speed you are probably doomed. But this would be the same with any other bike. Downside at this speed is that the downhill part of the journey is gone quickly, especially compared to uphill part.


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## Kell (5 Sep 2019)

I only meant it felt unsafe to pedal beyond around 25 mph as your legs are moving so quickly it upsets the balance of the bike.

And as Bromptons are fairly twitchy anyway, it feels more stable to coast and let gravity do the hard work. 

Obviously after that speed, I keep on accelerating.

There’s a guy I see on my train that was pedalling furiously down the same hill on a hybrid bike with 27 gears and couldn’t believe it when I coasted past him on my Brompton.

But then I did point out to him that gravity was definitely pulling down harder on me than him given i’m nearly 16 stone and he’s about 12.

Funnily enough, he always beats me back up the hill.


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## Handlebar Moustache (5 Sep 2019)

berlinonaut said:


> Just klick on the links in my last post.
> 
> 
> 
> My top speed with a Brommi on a descent was somewhat north of 70kph (the person behind my had a speedometer and stopped keeping up with me at 68kph as he considered it to be too frightening while I was accelerating further). I did not feel unsafe in any way and neither did the bike. Obviously if anything unforeseen happens at that speed you are probably doomed. But this would be the same with any other bike. Downside at this speed is that the downhill part of the journey is gone quickly, especially compared to uphill part.



They do say that you have to be careful braking a Brompton on long downhill stretches as you can heat up the brakes (and more importantly the rims) to dangerous temps. But in your case you weren’t braking so it’s fine


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## berlinonaut (5 Sep 2019)

Handlebar Moustache said:


> They do say that you have to be careful braking a Brompton on long downhill stretches as you can heat up the brakes (and more importantly the rims) to dangerous temps. But in your case you weren’t braking so it’s fine



Oh I was, as there were a couple of turns in the descent, some of them massive ones. I think the danger is overrated - it is mainly a question of braking technique. If you stand on the brakes on a longer descent the rim will heat up and in the worst case the tube may blow. If you let it roll and push the brakes only from time to time but push them hard then nothing will happen as the the rim will not heat up as much plus the heat can go in between the break intervals. In that sense on a Brommi a quick descent is safer than a slow one.


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## Kell (6 Sep 2019)

I must admit, in all my years of cycling I’d never heard of that until I had a blow out coming down the same hill at about 30mph. (But then I came from an MTB background so long stretches of braking were more likely to lock your wheels than overheat anything.)

Luckily, the Marathon Plusses are quite rigid so I was able to stay on. 

Other people suggested it could have been a build up of heat. In actual fact it turned out to be a badly adjusted front brake. 

From a visual check, the pads hit the rims exactly where I wanted them to, but one of the callipers was loose, so under extreme braking it would swing forward and rub the tyre.


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## mitchibob (12 Sep 2019)

Kell said:


> 83 does sound a little low, but I've not done the maths (and wouldn't have known where to start), but I do find it harder to spin quickly on a Brompton as opposed to my road bike. I've got a couple of those Sufferfest videos I use on the Turbo Trainer and at times you're spinning at 110RPM, which I feel would be almost impossible on the Brompton.



Super firm suspension. No issues spinning at 130+ rpm.


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