Brompton - 2-speed vs 3-speed

[citoyen]

I'm planning a new Brompton purchase and most of the decisions about spec are already made but one thing I can't decide on is gearing.

The current Brompton has a 3-speed Sachs hub, 54t chainring and 12t (I think) sprocket. I like this set-up so I'm tempted to replicate it as far as possible.

Am I right in thinking the 'standard' chainring size on a new Brompton is 50t? I'm struggling to find detailed spec on the Brompton website, only vague terms like 'standard' and 'reduced'. (And why do they no longer offer increased gearing options, only reduced? Oh well, at least the new style of chainset means it will be easier to fit a proper sized chainring.)

I'm also seriously considering the 2-speed option, but I've never used them before so how do they compare? I mainly use the low and middle gear, so I could probably live without the top gear. But again, it's hard to find any meaningful numbers. One thing I like about the 3-speed is that it's all internal, while the 2-speed derailleur is external. Does the 2-speed derailleur require more maintenance?

The other option is the 'black' edition, which both looks spiffing and comes with the 2-speed BSR gearing. That's an intriguing possibility. What is it like to use? It looks like the gap between gears is pretty big.

I still haven't ruled out the possibility of going for singlespeed. Ran the current Brommie as singlespeed for a while and loved the simplicity and reduced weight.

[Kim]

And why do they no longer offer increased gearing options, only reduced?

Because the standard option is horrendously over-geared?

I'm also seriously considering the 2-speed option, but I've never used them before so how do they compare? I mainly use the low and middle gear, so I could probably live without the top gear. But again, it's hard to find any meaningful numbers. One thing I like about the 3-speed is that it's all internal, while the 2-speed derailleur is external. Does the 2-speed derailleur require more maintenance?

The 2-speed seems like an excellent way to save weight (you need that tensioner anyway, so having it function as a derailleur doesn't add much).

AIUI the functioning of the derailleur mechanism does tend to suffer from accumulation of grot (or ice), so you can reasonably expect to have to de-gunk it a bit more often than the SS/hub gear version.  I don't have one, so can't say how quickly it becomes a problem.  What I can say is that the derailleur version of the idler wheels are cunningly designed to trap leaves and small pebbles, but once you're familiar with the symptoms it's only takes a second to flick them out.

I still haven't ruled out the possibility of going for singlespeed. Ran the current Brommie as singlespeed for a while and loved the simplicity and reduced weight.

I had mine as singlespeed for about a week, while I waited for the gears to arrive.  Once I'd put a much smaller chainring on it, it was surprisingly ridable (we have hills here), but that did seem to depend on SPD pedals and a willingness to spin at high cadence while making underwhelming progress on the flat.

I reckon the Brommie's limited top speed makes it particularly well suited to single-speed, but some experimentation may be needed to find your preferred ratio.

[marcusjb]

AIUI the functioning of the derailleur mechanism does tend to suffer from accumulation of grot (or ice), so you can reasonably expect to have to de-gunk it a bit more often than the SS/hub gear version.  I don't have one, so can't say how quickly it becomes a problem.  What I can say is that the derailleur version of the idler wheels are cunningly designed to trap leaves and small pebbles, but once you're familiar with the symptoms it's only takes a second to flick them out.

Kim's about right on the derailleur mechanism - I have one on my 6 speed Brompton.  Calling it agricultural would be an insult to those that work the land, but it does work well.  But, it sits where you don't really want something that needs to move freely sitting - it does get caked in road grime fairly easily and become a little lazy.  It does need a good clean every once in a while to keep it shifting properly.

I think if I were buying another Brompton, it would probably be a 2-speed, if not 1, to cut down on the weight of the hub gear etc.

[citoyen]

Because the standard option is horrendously over-geared?

 

I know I'm in a minority, but surely I can't be the only one who finds the standard set-up under-geared? Ho hum.

AIUI the functioning of the derailleur mechanism does tend to suffer from accumulation of grot (or ice), so you can reasonably expect to have to de-gunk it a bit more often than the SS/hub gear version.

it sits where you don't really want something that needs to move freely sitting - it does get caked in road grime fairly easily and become a little lazy.  It does need a good clean every once in a while to keep it shifting properly.

Hmmm. So I guess I'm right to be concerned... The 2-speed option does seem incredibly popular though.

I reckon the Brommie's limited top speed makes it particularly well suited to single-speed, but some experimentation may be needed to find your preferred ratio.

Yeah, maybe experimentation is the best option - after all, I didn't arrive at my current set-up without a fair bit of tinkering, and it's not really a big deal to alter the gearing. I should probably just get along to Evans to try one.

Singlespeed is a fantastic option for Bromptons IMO. And as for limited top speed, I still found it fast enough to beat Mr Zilla at the 2010 BWC.

[marcusjb]

You are right to be concerned, but it certainly should not put you off the 2 speed.  Just something you need to be aware of and depending on your cycle-hygiene routines, you may never experience any issues whatsoever.  If you are a dirty bugger like me, then, occasionally it will remind you to give it a scrub by being reluctant to do any of that derailling thing it is meant to do.

[LittleWheelsandBig]

Both HK and I run 6sp with standard 50t chainrings. I mostly sit in 4th or 5th gears in the flatlands. A 2sp would be annoyingly slow. The 3sp is a bit less annoying.

[rogerzilla]

The SA 3-speed (now called a BSR in Brompton branding, although it's actually an SRF3 with a short spindle) is a rather unexciting thing to pedal.  It won't slip but there's rather too much going on inside for my liking* and grease lubrication is actually higher maintenance; you are supposed to strip the thing annually**, clean it all up and relubricate it whereas an oiled hub just needs a few drops of oil (and I mean a few drops; any excess will run out so you are just trying to make up for evaporation) every few months.  I use older AW or AM hubs.

The least used gear on a 3-speed is the low gear, I find, so you'd want a 2 speed to be geared up.  With 12T and 16T sprockets this means a 54T chainring, and a 56T would be better.  Nice cruising gear of about 55" and a downhill gear.  You can stomp up most things in 55".

*the anti-slip or "No Intermediate Gear" design uses some rather flimsy bits of steel plate which rattle and get sticky, sometimes causing slow engagement of the pawls

**I stripped my SRC3 (a coaster brake version) recently after 30 months' hard commuting use.  It was pretty clean inside, even the actual brake mantle and shoes.  Pagid Cera-Tec grease (a couple of quid on the counter of your local Euro Car Parts) works very well on coaster brakes.

[citoyen]

The SA 3-speed (now called a BSR in Brompton branding, although it's actually an SRF3 with a short spindle) is a rather unexciting thing to pedal.

Is this different to the ancient 3-speed Sachs hub I have or essentially the same?

The least used gear on a 3-speed is the low gear,

For me it's the top gear. I suppose this is the benchmark for one's definition of over- or under-geared. YMMV, as they say.

With 12T and 16T sprockets this means a 54T chainring, and a 56T would be better.

[rogerzilla]

No, the Sachs hub uses the same ratios but is totally different inside.  The whole planet cage slides to change gear and it uses three planets, not four.  Jt's a very pretty little mechanism but not as well weathersealed as an SA hub.  Uses much thicker grease, too - SRAM IGH grease is a bit like gel toothpaste.

[citoyen]

Thanks, Roger - good knowledge.

As it happens, I ended up going to a Brompton press do last night and spoke to lots of people who work at the factory in various capacities. Apparently, everyone who works there rides an S2L. That sounds like a ringing endorsement.

I spoke to the chap who came second at this year's BWC and discussed the possibility of lowering the bars by fitting an S bar to an M stem. He advised against this, preferring a P stem - not so much for the height as the shape. And he doesn't use the S bar, he uses something wider to give more leverage to steering.

[rogerzilla]

I think the only times I've really used the low gear on a Brompton with normal ratios were on the FNRttS and when crawling over the Langdon Beck road from Weardale to Teesdale.  43" is ok for Chinnor Hill but not low enough for the north Pennines and I had to stop quite a few times.

The low gear on an AM is much more useful as it's only a 13.4% drop and therefore a good "headwind gear".  Likewise, the top gear is a 15.5% rise and a good "tailwind gear".  I heartily recommend this conversion to anyone, and you don't even have to rebuild the wheel.  You just unscrew and replace the internals, re-using your old spacers and nuts, so an AM with a really horrible shell (or a fairly useless 40h shell) is a good buy.  It's slightly lighter than the BSR, too.

http://www.ebay.co.uk/itm/Sturmey-Archer-AM-1954-hub-gear-vintage-40-hole-with-indicator-chain-alloy-/251972542135?hash=item3aaabbdeb7:g:3R0AAOSwpdpVY1aI

Personally I'd use an AW threaded axle key and the standard indicator chain, because AMs are designed for a two-piece right-through indicator which is fiddly, slightly unreliable (the two halves can unscrew on the road, meaning you gradually lose the lower two gears), sodding expensive if it breaks and has absolutely no technical advantage over the AW type.

[zigzag]

would the above conversion be quiet in use and compatible with the gripshift style shifter? i have a srf-3 hub which i might put in use. the main reason i stopped using it was the racket coming out of it (and draggy 3rd gear)

[rogerzilla]

Most SA hubs rattle a bit on rough roads, depending how much internal clearance you give them and how worn they are, but the SRF3 is particularly bad because of the extra shrouds around the pawls (extra SA grease may shut it up for a while).  Yes, AM cable pull is the same as an AW or a Sachs/SRAM 3-speed.  Technically I'm not sure the latter is precisely correct but it's close enough that (a) Brompton only make one shifter for both types and (b) Charlotte came 3rd in the BWC using an AM hub and a Sachs shifter.

Obviously if you fit AM internals into a current shell you either have to clean them up and lubricate "for life" with the modern SA grease, or add an oil port to the shell. I do the latter but the former is probably a lot less hassle.  An AM is no more difficult to strip down than an AW and has slightly fewer parts (!) but you MUST observe the little timing marks on the compound (stepped) planets when reassembling.  The marks must all point directly outwards (i.e. at 120 degrees to each other - there are three planets) from the sun gear at the point of assembly.  This will ensure they engage both the sun and the gear ring properly and smoothly despite the two being in different planes. Fail to do this and it will wear itself out faster than you can say "coffee grinder".

There's a photo of an AM mechanism,  minus gear ring, on the Wikipedia page on epicyclic gearing.  You can see the timing marks.

[Pickled Onion]

As it happens, I ended up going to a Brompton press do last night and spoke to lots of people who work at the factory in various capacities. Apparently, everyone who works there rides an S2L. That sounds like a ringing endorsement.

I had an S2L for years, and would not give it a ringing endorsement. Its replacement is an S3L.

The gearing is fine for around town, lots of stop-start at traffic lights, but not quite high enough for open roads. It requires a little more maintenance - the design is good with a lot of margin on the adjustment, but it does tend to refuse to shift when mucky and it wet weather.

However, the big issue is the hub design. There are two sets of bearings on the drive side, but the single cartridge on the non-drive side does not last long - mine failed in less than the life of the tyre. When it fails, it chews up the specially shaped aluminium nut that holds it in place. This nut is not available as a spare, I don't even think you can buy just the hub, so it's quite an expensive repair. I got through many sets of bearings - they're quite easy to replace - but would not buy a 2 or 1 speed because of this.

[citoyen]

Interesting, PO, thanks for that. I know which nut you mean, if it's the same as the one on the singlespeed hub.

[LittleWheelsandBig]

Same hub for 1 or 2 speed.

[fruitcake]

The Brompton I enjoyed test-riding in the hills around Guildford in 2011 was the S type with 2 speeds. The 3 speed hub geared Brommie I was given as 'a company car' was, alas, a dog.

[Kim]

The Brompton I enjoyed test-riding in the hills around Guildford in 2011 was the S type with 2 speeds. The 3 speed hub geared Brommie I was given as 'a company car' was, alas, a dog.

If that was an M-type I'd say the difference was more about geometry than the hub.  The S is a very different ride.

[fruitcake]

It was the M type. Different frame?

[LittleWheelsandBig]

Different bar height, mostly.

[fruitcake]

I know I was exhausted after a mildly hilly six-mile commute, so much so that a switch to a gas pipe MTB was a breath of fresh air.

I was similarly underwhelmed when I tried a new SA AW wheel on a Raleigh road bike a few years back. There was something unresponsive and unsatisfying about it. Swapping to a single speed freewheel made that bike fun to ride, even though I was out of the saddle on the ascents. Two-speed derailleur would have been just fine.

[Kim]

Different bar height, mostly.

Also reach.

[rogerzilla]

The M type is a bit like a Raleigh Chopper to ride, more so if you're shorter.  If you're about 5'10" or taller, the S type gives a bit of a drop to the handlebars, which is generally better for fast riding and climbing.

[Jakob W]

I really must try and find somewhere that has an S-type with the telescopic seatpost available to test ride; I can pootle perfectly happily on an M-type, but worry that the S-type would put me closer to an aero tuck...

[velosam]

If you as in London at all Evans at Kings across had one in.  I am in London on Friday so can check again if it helps.