4 speed Superlight Brompton

[berlinonaut]

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.

 

[gom]

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

 

[berlinonaut]

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).

 

[12boy]

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.

 

[Kell]

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.

 

[l4dva]

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.

 

[u_i]

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

 

[rogerzilla]

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

 

[Dogtrousers]

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.

 

[berlinonaut]

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.

 

[CaptainWheezy]

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.

 

[T4tomo]

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....

 

[berlinonaut]

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?

 

[T4tomo]

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.

 

[Kell]

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.