# 4 speed Superlight Brompton



## bikegang (18 Nov 2021)

P series Sprockets: 11-13-15-18 Tooth

Rear Wheel:

Superlight 4 speed rear wheel - Lightweight rim,

double-butted spokes and aluminium hub body with sealed bearings,

newly developed 4 speed freehub body and hex key axle


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## Cycleops (18 Nov 2021)

This super tit still isn’t exactly light at 10 kg except compared with standard.
Bit of an eye watering price.


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## FrankCrank (18 Nov 2021)

Superlight wallet after getting one of those


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## Kell (18 Nov 2021)

The big question (for me) is: Is it (going to be) possible to combine these four gears with any of the hub gears to get 12?


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## l4dva (18 Nov 2021)

Exciting - but yes expensive. I've been eyeing up a superlight since lockdown started but haven't pulled the trigger. Prices creep up and up, 1.5 years ago they where about £200/300 cheaper (slightly different specs now as they have changed a fair bit with P line).

I still want one, its just getting harder to take the plunge with price increase and drop to 4 speed, I feel like I need the 6 speed for the big hill I have on my commute. I'll have to try figure out if the new gearing option will work and convince myself its a good investment


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## CaptainWheezy (18 Nov 2021)

Looks good in theory but the gear range is a bit limited, and with the new style rear triangle, it doesn't have the extra bits needed welded on if you wanted to convert it to 6 speed, and means all these new parts are not backwards compatible. Wonder if superlights will now only be available as a 4 speed? Pretty limited if so, we have proper hills outside of London! I already have a superlight S6L (well, 2 actually) that are modified to weigh less than one of these thanks to the folks at Bikegang and SJS!


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## Tenkaykev (18 Nov 2021)

CaptainWheezy said:


> Looks good in theory but the gear range is a bit limited, and with the new style rear triangle, it doesn't have the extra bits needed welded on if you wanted to convert it to 6 speed, and means all these new parts are not backwards compatible. Wonder if superlights will now only be available as a 4 speed? Pretty limited if so, we have proper hills outside of London! I already have a superlight S6L (well, 2 actually) that are modified to weigh less than one of these thanks to the folks at Bikegang and SJS!


Ah! but have you swapped out the handlebar clamp Allen bolt for a Titanium one? I saved a massive 3 grammes when I swapped mine 😉( for aesthetic reasons. The bolts are always silver whatever the colour scheme, and I wanted a black bolt to match the stem / handlebars )


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## CaptainWheezy (18 Nov 2021)

Tenkaykev said:


> Ah! but have you swapped out the handlebar clamp Allen bolt for a Titanium one? I saved a massive 3 grammes when I swapped mine 😉( for aesthetic reasons. The bolts are always silver whatever the colour scheme, and I wanted a black bolt to match the stem / handlebars )



Haha, yes, i've done that, plus many more including all the nuts & bolts in the brake calipers.


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## tinywheels (18 Nov 2021)

a triumph of marketing over common sense.
you pays your money etc,etc ad infinitum


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## Cycleops (18 Nov 2021)

tinywheels said:


> a triumph of marketing over common sense.
> you pays your money etc,etc ad infinitum


Absolutely. And of course focus meetings.
You can tell the bean counters are well and truly in charge now as choice has been reduced and prices have increased.


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## tinywheels (18 Nov 2021)

they should concentrate on making the core product better. ie better quality components etc. they might find their customer base beginning to tire of these antics.


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## 12boy (19 Nov 2021)

I would like to see better pics of the derailleur set up and the hub/sprockets.


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## Biker man (19 Nov 2021)

bikegang said:


> P series Sprockets: 11-13-15-18 Tooth
> 
> Rear Wheel:
> 
> ...


Is


bikegang said:


> P series Sprockets: 11-13-15-18 Tooth
> 
> Rear Wheel:
> 
> ...


Is that the new P model it's £2100 that's a hefty price.


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## TheDoctor (19 Nov 2021)

Since Minimods / bikegang were offering a 4 speed conversion in 2017, I'm pretty underwhelmed.
See also - buy Brompton + Sparticle or Nano kit for lots less than E-Brompton.


Kell said:


> The big question (for me) is: Is it (going to be) possible to combine these four gears with any of the hub gears to get 12?


I doubt you'd get 4 sprockets on the BWR. 3 can be done - bikegang do that, or I think taking a 10 / 11 speed cassette to bits to get three sprockets and two spacers should do the trick. Then modify the shift lever or use a friction shifter.


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## Ming the Merciless (19 Nov 2021)

Agree at 10kg I would not put it in super light category. Light category in scheme if things but not super light.


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## tinywheels (19 Nov 2021)

if you had to spend the money a std brompton and a heap of mini mods bits would give you better bang for your buck I suspect.


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## Pale Rider (19 Nov 2021)

The bike offers a handful of incremental improvements which most manufacturers would make as a model year refresh.

Typical of dear old Brompton, it takes them 30 years.

There was a similar glacial development process with the eBrompton.


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## 12boy (19 Nov 2021)

I never got why the tensioner has to fit over the hubnut and wasn't made to screw onto the dropout area. Sure make it a bit easier to pull the rear wheel.


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## Cycleops (19 Nov 2021)

12boy said:


> I never got why the tensioner has to fit over the hubnut and wasn't made to screw onto the dropout area. Sure make it a bit easier to pull the rear wheel.


Because that allows them to use the existing subframe and not have to design a new one. Once again a decision made by accountants not engineers.


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## rogerzilla (19 Nov 2021)

I'll say one thing for Brompton - it may be slow progress and the price may increase wildly each year, but there is usually some product improvement in quality and/or design. The trend is always upwards*.

I've just pulled apart a late series 2 Moulton, built under Raleigh ownership. The de-speccing and cheapening that took place over 5 years is shameful. You can see the accountants' hands in the replacement of alloy parts with chromed steel, metal with plastic, hollow tubes with U-shaped stamped metal, no-name saddle and nasty pedals.

*paint comes and goes


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## tinywheels (19 Nov 2021)

I wrote to brompton a while back. suggested they offer a selection of bling bits as a way to boost income. bit like car dealers, upselling xtras. 
a common ploy in the retail sector. 
not their style apparently. 
meanwhile mini mods etc continue to have a buisness filling the void.


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## bikegang (20 Nov 2021)

12boy said:


> I would like to see better pics of the derailleur set up and the hub/sprockets.


There you go.
Its lock nut type free hub body. don't know if it has wider free hub body, but most likely not backward or BWR hub compatible (a new rear frame and chain pusher required anyway).
But the potential to get even wider gear range is there.


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## berlinonaut (20 Nov 2021)

Cycleops said:


> You can tell the bean counters are well and truly in charge now


Same goes for the moaners and haters in forums like this. No. matter what Brompton does oder doesn't do - the small predictable group of people will always find a reason to moan about it and to complain. No matter if there's a reason or not.



Cycleops said:


> Because that allows them to use the existing subframe and not have to design a new one. Once again a decision made by accountants not engineers.


Maybe you should at least look at the pictures of the bike you are commenting on - the P-line does have a different rear frame from the "usual" Bromptons.


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## tinywheels (20 Nov 2021)

berlinonaut said:


> Same goes for the moaners and haters in forums like this. No. matter what Brompton does oder doesn't do - the small predictable group of people will always find a reason to moan about it and to complain. No matter if there's a reason or not.
> 
> 
> Maybe you should at least look at the pictures of the bike you are commenting on - the P-line does have a different rear frame from the "usual" Bromptons.


as a brompton owner, there is quite a bit of moaning that's justified in my opinion. 
most of it could be sorted at little cost in my opinion. 
I like to think Brompton is to cycling what Morgan is to motoring.


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## berlinonaut (20 Nov 2021)

tinywheels said:


> as a brompton owner, there is quite a bit of moaning that's justified in my opinion.


Possible. Also, from the perspective of Brompton, a lot of moaning about forum comments and statements would be justified in my opinon. 


tinywheels said:


> most of it could be sorted at little cost in my opinion.


Most of it could be sorted with a little bit of thinking, less overestimation of the own relevance or cleverness, a bit of research before posting and adjusting own expectations to reality. 



tinywheels said:


> I like to think Brompton is to cycling what Morgan is to motoring.


Fun fact: There is no obligation to buy or own a Brompton. In fact many of the moaners don't own one. There are dozens if not hundreds of other folders available. If you are part of the constant-moaner-squad and still decided for a Brompton this probably says something. Not so many people that constantly moan about Morgan as it seems. Neither of the owner nor of the non-owners. Also I do have my doubts that anyone would rate a Morgan as the best sports car while a lot of people rate Brompton as the best folding bike.


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## 12boy (20 Nov 2021)

Wow that is complicated looking. It seems the derailleur is attached to the rear triangle in the back, by the axle and again where the chain pusher assembly used to be. Wonder if dropout was widened to allow for the old 1/2 speed hub?
Thanks for the pic BikeGang.


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## berlinonaut (20 Nov 2021)

12boy said:


> It seems the derailleur is attached to the rear triangle in the back, by the axle and again where the chain pusher assembly used to be.


Judging from the pic the tensioner and the derailleur may be two different, independent parts - this would also explain the two mounting points. Possibly the tensioner has one jockey wheel and the derailleur has the other one. Hard to tell.


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## 12boy (20 Nov 2021)

I did a little gear inch calculating and even with a 58 tooth chainring the 11, 13,15, 18 doesn't get above 85 gear inches while the 177% SA3 speed hits 96. Just sayin.


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## rogerzilla (21 Nov 2021)

This is why small-wheeled bikes, even the non-folding ones, often use hub gears. Having said that, how often would you use an 85" gear?


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## Blue Hills (21 Nov 2021)

mm - seems to me they are going the way, urged on by brompton's marketing whizzes, of the old salesman's company car - though they'll be paying for them themselves corporate climbers will be competing over the specs/extra flashes/model suffixes of their particular conveyance. How long before we're into the territory of the GTi 3sl*# ?
I'll stick with my 5 speed thanks.


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## berlinonaut (21 Nov 2021)

rogerzilla said:


> This is why small-wheeled bikes, even the non-folding ones, often use hub gears. Having said that, how often would you use an 85" gear?


I'd say "it depends".  I fully agree that the stock 3-speed with 50/13 is too long. On the other hand: For my taste the stock 2-sped with 54/12 is a bit too short, depending from my level of fitness. So for me a high gear of more than 6 meters of development but recognizably less than 7 meters or development is perfect - aroundish 6,50m. Both when using the Brompton in rather flat rather urban environments and me being no spinner but also no masher - cadence of around 75. The stock 2-speed offers 6m max, dependending from my level of fitness I change the 54t chainwheel to 60t, resulting in 6,65m development / 83 gear inches (relatively similar to the highest gear of the 4-speed). Since Corona I rely on the 54t chainwheel...

3-speed vs. 4-speed





2-speed setups vs. 4-speed








On the other hand: When touring I clearly prefer a wider spread of gears and shorter gears than the 2- 3- and 4-speed offer are already necessary in a hilly urban area. This is where my modified 9-speed BWR shines. With 44/12-14-16 the highest gear is at 7,64m - in practice enough but I have to live with spinning out downhill sometimes. The short end is at 2,33m and this is still too long for some serious hills, let alone with a lot of luggage. My Rohloff Brommi does overcome these limitations - with a 50t chainwheel the upper end is at 7.50m and I hit this regularly. With a 54t chainwheel the upper end is at 8,10m and I very rarely use that gear. The lower end is at 1,43m with the 50t and 1,54m with the 54t chainwheel - both barely used, only on the steepest of steep hills.

9-speed BWR vs. Rohloff with 50t and 54t




My personal conclusion is to have two main Brommis: One with the 2-speed and one with the Rohloff. I could and can do everyhting with the Rohloff one but the 2-speed titanium is 3-4 kg lighter, the drivetrain feels more direct and I generally like the "reduced to the max" feeling of the two speed. So it is nippier and does have a totally different character.

So overall from my personal perspective the new 4-speed setup is not very attractive: It is not as reduced as the 2-speed and while the higher high gear is nice it is less flexible, nothing not already achievable today plus it still does not solve the issue of getting stuck on hills relatively early. I also find the claim of Brompton _"1,5 kg lighter than the comparable steel Brompton"_ misleading as they do use the 3-speed hub as a comparison. The 2-speed would be a more adequate alternative in my eyes. But then the weight difference would be just 700g, same as it used to be with the old titanium/superlight model... Harder to market.


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## gom (21 Nov 2021)

Will Rohloff ever make a Brompton-compatible hub? That's what I'm waiting for.


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## berlinonaut (21 Nov 2021)

gom said:


> Will Rohloff ever make a Brompton-compatible hub? That's what I'm waiting for.


A Rohloff Brompton is just a call to Glasgow away. So no need to wait - you can have one today. A Rohloff Brompton will - as any Rohloff bike - never be a mass product. So no incentive for Rohloff to develop such a special hub even if Brompton would ask them. Since the Rohloff hit the market in the late nineties they do build more or less exactly the same hub - they are mainly a one-product-company. Plus I do have my doubts if it would be technically possible. If you look at the internals of a Rohloff hub






I do see not a realistic way to slim it down from 135mm to 112mm width. Way easier, simpler and more pragmatic to go down the Kinetics route and to widen the Bromptons rear triangle (as steve Parry did and possibly still does) or to construct a new one (as Ben Cooper did).


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## 12boy (21 Nov 2021)

Rogerzilla, as a grinder, not a spinner l like a cadence of around 60 RPM. From the highest point I usually ride to the lowest is a drop of 600 ft in about 4 miles and yesterday with my 96" high gear l was comfortable going down the grade. It is fairly windy here, though, and I like to drop down to around 72 gear inches, even on the flats when the headwind is fairly stout. I am pretty happy with my 58 and 38 chainrings and the 11/14/17 sprocket gifted me by BikeGang as a demo, but am not too keen on wearing out the 11 tooth part as it is a onepiece unit. So l took off the chainpusher, threw a $7 13 sprocket on it and plan on using the SA 3speed on dry days this winter and the 13 tooth wheel with front and aft snowtires on icy days without too deep a snow. If it gets too deep, l have an old 'dale mtn bike with studded snows. ln the summer the range of the BikeGang three speed and its lightness is pretty nice.


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## Kell (23 Nov 2021)

Just as an aside, a friend of mine went in to the Brompton Junction in Covent Garden to have a look at the new bike, but they didn't have any in stock.

However, the sales guy did say they're bringing out a 9-speed soon.

He did not go on to clarify whether or not this would be a Super-light. I suspect not.


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## l4dva (23 Nov 2021)

Kell said:


> Just as an aside, a friend of mine went in to the Brompton Junction in Covent Garden to have a look at the new bike, but they didn't have any in stock.
> 
> However, the sales guy did say they're bringing out a 9-speed soon.
> 
> He did not go on to clarify whether or not this would be a Super-light. I suspect not.




Interesting! I wonder how they are getting to 9 speeds - 3 speed internal hub x 3 speed external cassette? 

I think a big chunk of the 1.5kg weight saving on this 4speed superlight is from ditching the internal hub gearing for the external cassette. I'm sure I've seen mod'ed bromptons with larger cassettes than 4 speed on you tube in the past. Would certainly be lighter than a internal hub. Although I totally understand the appeal for the hub gearing and all the benefits that come with that.


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## u_i (23 Nov 2021)

I hope this new derailleur is compatible with the triangles produced thus far. There is obviously a project or two there in the making


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## rogerzilla (23 Nov 2021)

Left and right chainrings and 4 1/2 cogs on each side, I reckon


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## Dogtrousers (24 Nov 2021)

Kell said:


> However, the sales guy did say they're bringing out a 9-speed soon.


3 sprockets plus a three speed hub gear? 

That could provide interesting mental gymnastics if you are the kind of nerd who wants to proceed through the gears strictly in order.


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## berlinonaut (24 Nov 2021)

Dogtrousers said:


> 3 sprockets plus a three speed hub gear?
> 
> That could provide interesting mental gymnastics if you are the kind of nerd who wants to proceed through the gears strictly in order.


That's not too tough. 3*3 has become a regular customization over the last years. Here's my setup:






https://ritzelrechner.de/?GR=BBWR&KB=44&RZ=14,12,16&UF=1330&TF=75&SL=2.6&UN=KMH&DV=development

Shifting is pretty linear (three times derailleur, then one time hub) and nicely spaced in this variant. Not more confusing than the actual BWR.


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## CaptainWheezy (24 Nov 2021)

3 x 3 might make a bit more sense in your head if the hub gears were swapped to the left hand shifter since they would become more like the gears on a tripple chainset, then the external 3 become more like a somewhat limited casette on a road bike.


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## T4tomo (24 Nov 2021)

Ming the Merciless said:


> Agree at 10kg I would not put it in super light category. Light category in scheme if things but not super light.


Its heavier than my 2005 superlight 3 speed. Clearly a titanium seat post (which they can no longer reliably source) is a bigger weight saving than switching from a 3 spd hub to this new 4 speed cassette & chain pusher.

Its a nice alternative for people who, for whatever reason, don't want hub gears, and it does give a closely spaced sequential decent gear range, which the other options don't offer.

For an all weather commuter, hub gears are perfect, but then Brompton doesn't only sell to all weather commuters....


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## berlinonaut (24 Nov 2021)

T4tomo said:


> Its heavier than my 2005 superlight 3 speed. Clearly a titanium seat post (which they can no longer reliably source) is a bigger weight saving than switching from a 3 spd hub to this new 4 speed cassette & chain pusher.


I'd have my doubts regarding that. The difference between the 2-speed and the 3-speed is about 700g. The 4-speed is probably a tad heavier than the 2-speed, still there will be a difference of at least 500g, probably more.
The former Brompton ti-post saved around 100g in comparison to it's steel counterpart, according to the Brompton 2005 catalog. In practice it was a bit more and obviously the gain varied slightly depending from standard/extended or telescopic post. Nevertheless the weight saving was never even close to 500g, let alone higher. 

Brompton themselves said 2005 the weight saving on the superlight was 790g, plus 100g through the optional ti-seatpost and another 25g though the optional ti-folding-pedal bolt. The latter two do not exist anymore and the claimed weight saving of the superlight has varied a bit over the years. The superlight bits have consistently been ti forks, rear frame and mudguard stays plus an aluminium headset. In the early years the S-model did have a lighter saddle (Fizik Vitesse) plus the pentaclip (became standard only in 2009). 

On newer Bromptons some features like i.e. the spider crank and the double wall rims are slightly heavier than the fixed chainwheel and the single wall rims of a 2005 model, on the other hand they are probably worth it.

Still I can hardly believe that a 2005 3speed superlight with a comparable feature set (same bar type, carrier block, mudguards, battery lights) would be recognizably lighter than an actual P-Line if at all. The P-Line equivalent to a M3Lx i.e. is quoted at 9.89kg in the Brompton store (including all those features). S and H (low and high) models are quoted with the same weight though there clearly is a bit of a weight difference between those. What model do you own and what does it weight?


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## T4tomo (24 Nov 2021)

Mine is/was an SL3 model, which was lighter than the M (-145g) and yes I had the Vitesse saddle and I think it came in at gnats knob under 10KG, which was the weight being quoted for the P line. defo not recognizably lighter, but I didn't claim that.

The point remains, the P line isn't revolutionary light (indeed the 2005 SL2 was 630g lighter than the SL3) as some of the improvements over the 16 years you mentioned weigh a bit more, all its done has reversed some of that bloating to get back to ~10kg.

There isnt much lighter a brommie will go as long as it keeps it steel mainframe.


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## Kell (24 Nov 2021)

I think the whole gearing conversation about the SL is an interesting one. Like @l4dva, I'd assumed that having four cogs and no hub gearing is 'better' for weight saving compared to the 3-speed even if it gives a similar (slightly reduced) spread of gears.

It's not often that I need a wider spread of gears than my 6-speed provides for example, but I'd love the gaps between them to be less comically large. At present it doesn't quite suit my cadence - but I realise this might only apply to me.

My two most used gear are 4 and 5. I "THINK" that for the same speed there's a difference in RPM of +/- 15-18 RPM*. So at (for example, not sure this is factually correct) at 16mph I could be pedalling at 88 RPM in 4th, which is too high. Change to 5th and it drops to 70 RPM (ish) which is too low.

*Not all measured scientifically or accurately.

I think before lockdown I was happier at low 70s, but since lockdown I've been using my ROad bike a lot more - especially on the Turbo Trainer and my natural cadence has gone up. SO that now, I'd be more comfortable at around 80.

Tried the smaller 46T chainring in the past (mainly to get a lower lowest gear), but that knackered the top end and left me spinning out too often. Not tried going up a size as I need the current low gearing as part of my regular journey.

Having an intermediate gear would be ideal to split the difference. I know it's doable currently with non OEM parts. but not made that commitment yet.


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## Kell (24 Nov 2021)

berlinonaut said:


> That's not too tough. 3*3 has become a regular customization over the last years. Here's my setup:
> 
> View attachment 619112
> 
> ...



Is it possible to use that gear calculator to measure RPM? Or can the figures it spits out be interpreted to see if my guestimate of 15-18RPM (ish) between gears is correct?


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## Kell (24 Nov 2021)

Kell said:


> Is it possible to use that gear calculator to measure RPM? Or can the figures it spits out be interpreted to see if my guestimate of 15RPM (ish) between gears is correct?



OK - so It doesn't seem to directly give you that answer, but by pulling the cadence slider about, you can see that to get 15.1 mph in 4th would be 79 RPM and in 5th it would be 62RPM - so 17RPM or roughly where I thought.


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## berlinonaut (24 Nov 2021)

T4tomo said:


> The point remains, the P line isn't revolutionary light (indeed the 2005 SL2 was 630g lighter than the SL3) as some of the improvements over the 16 years you mentioned weigh a bit more, all its done has reversed some of that bloating to get back to ~10kg.


Fully agree with that as I wrote earlier:



berlinonaut said:


> So overall from my personal perspective the new 4-speed setup is not very attractive: It is not as reduced as the 2-speed and while the higher high gear is nice it is less flexible, nothing not already achievable today plus it still does not solve the issue of getting stuck on hills relatively early. I also find the claim of Brompton _"1,5 kg lighter than the comparable steel Brompton"_ misleading as they do use the 3-speed hub as a comparison. The 2-speed would be a more adequate alternative in my eyes. But then the weight difference would be just 700g, same as it used to be with the old titanium/superlight model... Harder to market.


They are probably doing a bit of overmarketing here.


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## u_i (24 Nov 2021)

Kell said:


> However, the sales guy did say they're bringing out a 9-speed soon.



This is really exciting.



berlinonaut said:


> That's not too tough. 3*3 has become a regular customization over the last years. Here's my setup:
> 
> Shifting is pretty linear (three times derailleur, then one time hub) and nicely spaced in this variant. Not more confusing than the actual BWR.



In my experience, the pusher system has not been well suited for the shifting to an intermediate cog. I would list at least 3 indicators for that. 1. The tolerance in the cable pull has been far more narrow for proper shifting than in the standard rear derailleur systems. 2. The shifting to the intermediate cog would generally not work unless the smallest and intermediate cogs were matched (came from the consecutive positions in the donor cassette). Standard derailleurs usually tolerate mismatched cogs. 3. Sticky snow would disable the 3-cog shifting on Brompton far sooner than for similarly low placed standard derailleurs on other bikes. Yes, I ride with 3 cogs on Brompton myself, and it works OK, but on the technical side I view it as a 'get by' solution'.

With all that I look forward to seeing what Brompton came up with for the purpose. The standard derailleurs fit poorly in the space there and their tensioners are marginal in picking up slack compared to the Brompton tensioner. I hope that latter capability is not compromised.


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## Dogtrousers (24 Nov 2021)

berlinonaut said:


> Shifting is pretty linear (three times derailleur, then one time hub) and nicely spaced in this variant. Not more confusing than the actual BWR.


So shift with your left (sprocket) until you hit the end of travel of the left shifter. Then shift the left shifter all the way the other way and shift with the right (hub). So starting in bottom gear it goes L, L, L&R, L, L, L&R, L, L.

My 6 speed goes L, L&R, L, L&R, L. I think I'd find the 9 speed pretty confusing. But I'm easily confused!


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## u_i (24 Nov 2021)

Dogtrousers said:


> So shift with your left (sprocket) until you hit the end of travel of the left shifter. Then shift the left shifter all the way the other way and shift with the right (hub). So starting in bottom gear it goes L, L, L&R, L, L, L&R, L, L.
> 
> My 6 speed goes L, L&R, L, L&R, L. I think I'd find the 9 speed pretty confusing. But I'm easily confused!



I moved my hub shifting to the left and sprocket to the right, to make it consistent with other bikes: big jumps on the left and small on the right. I try to make other things consistent too, like bell and light, to reduce reaction times.


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## Dogtrousers (24 Nov 2021)

u_i said:


> I moved my hub shifting to the left and sprocket to the right, to make it consistent with other bikes: big jumps on the left and small on the right. I try to make other things consistent too, like bell and light, to reduce reaction times.


This has crossed my mind, too. But I've got used to it now.


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## Kell (24 Nov 2021)

u_i said:


> I moved my hub shifting to the left and sprocket to the right, to make it consistent with other bikes: big jumps on the left and small on the right. I try to make other things consistent too, like bell and light, to reduce reaction times.



Did you need to switch shifters somehow too?


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## u_i (24 Nov 2021)

Kell said:


> Did you need to switch shifters somehow too?



I put twist shifters on. I got used to them on other bikes and, for me, they allow for faster, near perpetual, shifting.


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## Kell (24 Nov 2021)

That makes sense. Ta.


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## bikegang (25 Nov 2021)

l4dva said:


> Interesting! I wonder how they are getting to 9 speeds - 3 speed internal hub x 3 speed external cassette?



TBH, 9 speed with a BWR hub will have a lot of redundent gears, making it all more complicated ...


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## berlinonaut (25 Nov 2021)

bikegang said:


> 9 speed with a BWR hub will have a lot of redundent gears


No, as shown earlier in this thread. It all depends from how you choose your sprockets. 2 teeth apart and you are fine.


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## Kell (25 Nov 2021)

TBH - 9 speeds to me is only achievable in a few ways.

1x3x3. Probably the cheapest solution as it would utilise their existing 3-speed BWR hub and then three sprockets.

1x9. Where you have a cassette, a short cage derailleur and a modified rear wheel or new rear triangle to make additional room.

3x3. Where they add two more chainrings AND an additional sprocket and use a single speed rear wheel. This actually makes more sense than the 1x9 to me. Or at least feels more achievable. 

I don't see the second one working, I'm not sure there's enough space even if you take out a lot of the dish on the rear wheel. So *IF* *what the guy said is true, the most obvious solution would be the addition of an extra sprocket.

*Obviously, it's just a rumour. Google 9-speed Brompton and so far, nothing comes up - except the aftermarket solutions. But by the same token, I don't think my friend would lie to me about it, so he's just taken what he was told at face value... time will tell.


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## TheDoctor (25 Nov 2021)

The simplest 9 speed by far would be the BWR hub with, say, 12 14 16 or 13 15 17 sprockets. 9 gears and a slightly wider range.


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## rogerzilla (26 Nov 2021)

Giving the BWR a wider range would mean impracticable gear sizes internally. You'd need a very big sun and, given that the OD of the shell is limited, the planets would be too small - the ratio of a single epicyclic is given by the teeth of (sun+gear ring)/gear ring. The BWR already pushes it about as far as it can go.

You can use cascading gear trains but they are pretty inefficient. You lose at least 3% in an epicyclic with perfect tooth shape and lubrication, but over 6% in a two-stage hub.


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## Dogtrousers (26 Nov 2021)

Kell said:


> TBH - 9 speeds to me is only achievable in a few ways.
> [...]
> 3x3. Where they add two more chainrings AND an additional sprocket and use a single speed rear wheel. This actually makes more sense than the 1x9 to me. Or at least feels more achievable.


Maybe dumb questions but ...
Where would you put the front mech?
Would you need a longer chain tensioner?
Would folding be affected?



rogerzilla said:


> Giving the BWR a wider range would mean impracticable gear sizes internally. You'd need a very big sun and, given that the OD of the shell is limited, the planets would be too small - the ratio of a single epicyclic is given by the teeth of (sun+gear ring)/gear ring. The BWR already pushes it about as far as it can go.
> 
> You can use cascading gear trains but they are pretty inefficient. You lose at least 3% in an epicyclic with perfect tooth shape and lubrication, but over 6% in a two-stage hub.


Interesting. As I don't know anything about hub gears my proposed solution to this kind of problem is generally to point at the hub and say "do more magic inside there".


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## berlinonaut (26 Nov 2021)

TheDoctor said:


> The simplest 9 speed by far would be the BWR hub with, say, 12 14 16 or 13 15 17 sprockets. 9 gears and a slightly wider range.





rogerzilla said:


> Giving the BWR a wider range would mean impracticable gear sizes internally.


The slightly wider range in this setup is not a result of a change of the BWR but of a wider spread in sprockets. From factory the BWR is equpped with 13-16, in i.e. my 9-gear setup I use 12-14-16. So one tooth more spread, resulting in a slightly wider range than the original BWR-based 6-speed.


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## berlinonaut (26 Nov 2021)

Dogtrousers said:


> Maybe dumb questions but ...
> Where would you put the front mech?
> Would you need a longer chain tensioner?
> Would folding be affected?


As usual on the seat tube. Solutions exist for more than 20 years from various sources over the years. Today you can source a clamp for the front mech on Asian marketplaces. Typically no need for a longer tensioner though - depending from the difference in chain-wheel size - in many cases it is not recommended to fold with the chain on the smaller chainwheel. For that reason I don't think Brompton would go down that route from factory - it adds complexity as well as cost and is not foolproof enough for an innocent user.
Apart from that a double chainwheel-setup works very well in practice. I do currently use one as a granny-gear setup on my two-speed (ATM 53-39/12-16).



Dogtrousers said:


> Interesting. As I don't know anything about hub gears my proposed solution to this kind of problem is generally to point at the hub and say "do more magic inside there".


That's the proper classical management approach!


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## 12boy (26 Nov 2021)

A front derailleur has not proven necessary for me as I rarely use the smaller chainring. When I do use it is a granny gear setup for long steeper grades and/or stout headwinds. The tensioner works just fine, BTW ,except folding needs to be done with the chain onthe big chainring.
There is an SA 4 speed hub that is close to the 3 speed in weight with a 210% range and with direct drive in first gear. It has a 120mm OLD. Having first as the direct drive would allow for some pretty tall high gears with a smaller chainring. I have no idea where to buy such a hub, though.


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## berlinonaut (26 Nov 2021)

12boy said:


> There is an SA 4 speed hub that is close to the 3 speed in weight with a 210% range and with direct drive in first gear. It has a 120mm OLD. Having first as the direct drive would allow for some pretty tall high gears with a smaller chainring.


Interesting. Possibly it could fit the Brompton rear triangle after minimal modifications to the hub w/o spreading the rear triangle. This is the case with it's bigger brother X-RF8 in 120mm. Still I am not sure if the X-RF4 would be desirable. The X-RF8 also has the first gear as direct gear and in practice it lacks efficiency in higher gears (at least subjectively) plus mechanically I would not call it first choice. I had it in my Brompton for a couple of years and have moved it to the Brecki (where it is a surprisingly good fit as this is a more relaxed bike anyway).
Anyway: With two chainwheels the X-RF4 offers 315%, so not much more than the BWR and less than the X-RF 8. Also the spacing is kind of ok but not too nice: https://ritzelrechner.de/?GR=SAX8&KB=54,36&RZ=19&UF=1330&TF=75&SL=2.6&UN=KMH&DV=development

When looking for an alternative for the 3-speed hub I'd rather point to the S-RF5 that superseeded the sprinter. It it solid, has a 256% spread, not heavier than the three-speed, available in 112mm OLD/28 spokes and can even be tweaked to take two sprockets. For unknown reasons is has vanished from S/A's webpage already years ago but used to be available i.e. at SJS until recently (though currently n/a, documentation still there) and you can get it as a 5-speed or 10-speed hub or prebuilt wheel via Brommiplus: https://www.brommieplus.com/portal_c1_cnt.php?owner_num=c1_343119&button_num=c1&folder_id=44131

Also not my first choice and with 2 sprockets you'll have a hard time figuring out a really good setup: https://ritzelrechner.de/?GR=SAX5&KB=44&RZ=16,12&UF=1330&TF=90&SL=2.6&UN=KMH&DV=development

With a single sprocket however it is a direct and simple replacement for the three speed and does a good job with an enhanced spread 177% -> 256% with a single shifter. The gear jumps are however pretty high and adjustment of the hub is a bit sensitive (but not as bad as with the X-RF8).


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## TheDoctor (26 Nov 2021)

Having crunched the numbers, my personal bet for a 9 speed Brommie would be the BWR and 13/15/17 sprockets.
That gives a gear range of 30, 34, 39, 47, 54, 62, 74, 84 and 97 inches, and next time I replace the transmission I'll probably go down that route.
For comparison, my M12R currently has BWR, 50/44 chainset and 13/16 sprockets.
Gear range of 32, 39, 50, 62, 79 and 97 inches on the 50T ring, which is standard.
The 44T ring gives 28, 35, 44, 54, 69 and 85 inches, which suits me better for touring. I got up a 1:7 iirc with luggage on that setup, doing a Hadrians Wall ride from Carlisle to Newcastle.


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## berlinonaut (26 Nov 2021)

TheDoctor said:


> I got up a 1:7 iirc with luggage on that setup, doing a Hadrians Wall ride from Carlisle to Newcastle.


If Hadrian had had a Brompton back then to patrol his wall he'd probably have gone for the same setup!


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## TheDoctor (26 Nov 2021)

I hope he'd have done better than me. I was utterly cream-crackered by the time I got to my overnight stop at Heydon Bridge. I struggled with my main, only just managed to finish my chocolate fudge cake, and quite possibly left some beer. Most unlike me!


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