Brompton owners

https://www.sturmey-archer.com/en/products/detail/csisw-flat

1/8" flat 3 spline sprocket.

"Available in 13 to 22 teeth sprocket"

Duplicate post

Shall we say, were dealing with a 6 speed hub per op so I'm sure +jj72 is on the same page too with regards to the 3/32 cogs not 1/8.

I'm not really sure what you're saying.

jj72 said 1/8" cogs not made/available, I was just posting things to prove otherwise.

For clarity, I don't know what width cogs the derailleur bikes use now or have used in the past, I'd have presumed 3/32" so that you could use a 3/32" geared chain but jj72 post seems to suggest it used to be 1/8" cogs.

The current 2/6 speed cog kits have what appears to be a plain toothed smaller cog and a larger cog with ramps and pins.

If there were 3 splined cogs with ramps and pins fitted to older 2/6 speed bikes then yes, I can see that those are no longer available. Or maybe the cogs were a special thickness in order to work with the drivers which (I think) were primarily designed to work with single cogs and these are not available anymore.

However, it seems like you can make it work with plain toothed cogs which are available, in 3/32" and 1/8" and down to 13t so @hugo7 father's could be sorted out without the new rear wheel.

Maybe the shop that's doing the work can't source the cogs from their suppliers or they need a bit of modding which the shop can't/won't do which is fair enough but there are definitely ways and means and Sturmey/3 spline cogs are definitely still available.

Yup, the Sachs 6 speed used 1/8th sprockets. As you say there are some available on eBay and some places may have NOS, but that’s not really an option for a business like ours. I don’t have time or tools to make spacers up- I’ve tried, and it’s a faff. Tbh most Brompton wheels of that age will have worn rims anyway and probably due for replacement, so a new wheel makes sense to avoid future sprocket anxiety issues.

“Sturmey currently have at least 19 models of hub on this page that take that size of 3 spline sprocket, you're telling me they are offering that many hubs but just don't make 1/8" cogs to support them?”

Not in 13t, no. According to my suppliers.

Also, I checked with SJS and they told me they’re out of stock, so who’s right?

Yup, the Sachs 6 speed used 1/8th sprockets

Sorry, this is not correct. I have owned a 2002 T6 from new and the chain was 3/32". The T3 had a sprocket for a 1/8th chain, like the earlier 3- and 5-speed SA versions.

As shown in the link I posted above to the T6 sprocket set parts diagram QRSPRSTACK-SR6, the width of the sprockets at the hub was 2mm and 3mm for the inner and outer sprockets respectively, the latter was machined on the inside face to fit the 3/32" derailleur chain.

As you say there are some available on eBay and some places may have NOS,

I’m sorry but these 1/8” sprockets including the low tooth counts are far too widely and cheaply available for me to believe they are coming from a finite nos source.

Between Alfine/nexus, Sturmey and Sachs IGHs and various coaster hubs I’ve been using and buying 3 spline cogs for well over a decade and I’ve not seen much if any drop off in the availability of cogs.

In the uk we might be all about 12speed electronic shifting and such but I’m sure there are places not too far from here where 95%+ of bikes are running on hubs that take 3 spline cogs. They are not some forgotten about antiquity.

but that’s not really an option for a business like ours. I don’t have time or tools to make spacers up- I’ve tried, and it’s a faff.

I totally understand this.

most Brompton wheels of that age will have worn rims anyway and probably due for replacement, so a new wheel makes sense to avoid future sprocket anxiety issues.

Also very true.

OK so my head is spinning a bit from all of this.

But to summarise:

1. It is possible for a retail consumer to buy 1/8 cogs that fit the hub in the requite tooth
   
2. Bromptons require thinner sprockets for the inner two
   
   
   

Worth me saying that for my dad having a slightly higher tooth count isn't going to be a deal breaker.

It's a shame I'm so time short now with kids and everything as in the past this is exactly the sort of thing I'd have done for him.

It is possible for a retail consumer to buy 1/8 cogs that fit the hub in the requite tooth

It is 100% possible to buy a low tooth count 1/8” cog to fit the hub as a consumer.

I have no idea how possible/easy it will be to make more than one of these cogs fit on the hub or how well the (derailleur) gears would work but it does seem people have done it.

Pick a 1/8” chain without protruding rivets to minimise the minimum gap required between cogs. Run a 13/15t or 14/16t combination. Possibly sand one side of the circlip to sneak out another 0.2mm width. Possibly sand down the spacer between cogs for another 0.1-0.2mm. That used to work on F&S and SA hubs.

The 1/8" chain shifts between the cogs alright?

I’ll say it again - none of our trade suppliers here have 13 or 14t 1/8th 3-spline sprockets. SA don’t make them any more. I’m not making this shit up.

Also waiting for @sbbohr to turn up and put us straight.

Second THAT!

g'evening.

Firstly, Sachs / Sram hubs have no spares available so owning one is a ticking time bomb!

Secondly, to get the "correct" ratios the hub uses a 13/15t set up, 1/8th pitch.

The tooth profile is also a bit odd, there are not dropout profiles like most sprockets have instead one tooth is much smaller in height etc.

Its a bit of a minefield, I used to care about finding some, I could easily have a few million made via SJS but most of the hubs have shit themselves by now and it just makes more sense to go with a BWR even though the initial cost is somewhat

The Brompton DR system is not super precise, so you can often get things to work, but it is also easy to fit stuff that just wont work however hard you try ...

Yes, just fitting a single sprocket would be a cheap option

Sunrace have several things in their catalogue that they could make but won’t actually make until a company places a large enough order. The aftermarket alone usually isn’t big enough to start the production line rolling.

If you are looking at keeping just one bike running, your priorities are quite different to someone running a bike shop. Grinding a tooth lower on a 1/8” 15t cog might be worth the effort to use an obsolete hub until an internal component breaks.

1/8” chain shifts just fine. Derailleur gears have been fitted to Sturmey hubs for a century.

The issue for smaller SA sprockets - 13 & 14 tooth- is that only small wheeler bikes like early Bromptons and original Moultons use them. There just isn’t the demand for them to make it viable for production.

Also, Sachs hubs were largely bollocks anyway.

I still love my F&S Duomatic. I don’t think a better hub gear has been made.

Thanks for all the input guys.

I used to have a 3 speed coaster hub that must have been from right around when they changed from Sachs to Sram, half the stuff was branded one way, the rest the other.

Best igh and best coaster brake I've used.

It needed some sort of almost proprietary threaded axle nuts though so that was a pita.

“It needed some sort of almost proprietary threaded axle nuts though so that was a pita.”

Not ‘almost proprietary’ but ‘actually proprietary’. Both Fitchel & Sachs and Sturmey Archer were old enough companies that the concept of national or international thread standards is more recent than their founding.

I still love my F&S Duomatic. I don’t think a better hub gear has been made.

The Fichtel & Sachs Duomatic is also my favouring hub gear (and it suits a separable Moulton very well -- no cables). I also have a new-old-stock F&S Automatic hub put aside for some future project. The build quality and longevity is something else altogether for these hubs, plus the weight is reasonable as you save on a rear caliper brake.

Query: stem reach.

TL:DR version:

• 2021 model, started with a H stem and bars, now with flat bars+ bar ends, having improved injuries. Want a bit more reach. Saddle is already set back to optimal position.
  
• Which Brompton stems, if any, have longer reach to bars?
  
• Can I obtain one without having to have a shop fit it? (Qualified, experienced former workshop mechanic).
  
  
  

Longer version:

So, have been enjoying my H Type Brompton since purchase around 6 months ago. As I have managed to improve on back and hip injuries, I have been gradually dropping the bar height from stock, to 10cm rise, to 5cm rise, down to flat bars.

(This was the plan, thus being able to stick with higher bars if the injuries persist and shorten cables as needed).

Now, with the flat bar, the bar is pretty much level with saddle. It's about right for my current physical state - could maybe use a 10mm riser bar to tweak.

But, now the bar is lower than stock, I feel I could do with a bit more reach: I suppose with higher rise bars higher than the saddle, the grips were further from the saddle (same as when bars are lower than saddle) than when level. I was also able to tip the bars forward a bit - obviously not possible with flat bars.

I probably want the bars about 20mm further forward. That would put the bars the same distance as the flats on the drop bars of my touring bike, with bar ends to vary grip.

The saddle is already quite far back: saddle nose 70-75mm from BB, to match my 'proper' bikes, so that's not the issue.

I have been trying to find out about the different stem types and bar reach but there is conflicting information about pre / post 2017 models. It seems like the S-Stem has longer reach than H, but I can't find anything definitive.

If the S stem is longer reach, I would be tempted to go for one, if it would put the bars in a similar position. I gather seems to be around 20mm of wiggle room re. height, to add low-riser bars if you need to raise bar height on an S stem without affecting the fold.

Also, if I did this, does anyone know a way of getting hold of a stem to fit at home?

SJS were great in obtaining the bike and initial mods, but (a) I'm not inclined to post the whole bike back across the country to have it fitted, with the risks inherent in posting expensive stuff (b) am a qualified and experienced mechanic myself (diff. job now) but tight on cash, so it would hurt to pay a wedge taking the levers, grips on and off etc. and (c) would trust myself than what I think are the only local Brompton dealers.

I know that sounds cranky but once you've worked in a shop and had to sort cock ups coming in from another shop, (and learned through your own mistakes) you end up only trusting yourself and selected colleagues and shops. I supposed I could insist they just swap the stem and I can deal with levers, cables, etc.

From a brief check, I understand that the current model is a wedge-type quill stem, which takes 30nm, rather than the older expander-types which were 15nm. I would obviously check again before doing the work...