Brompton 3-speed hub
 

The Brompton comes in 3-speed and 6-speed models, but I was wondering if the 3-speed hub gearing is identical on each model. For me, I like having the extra gear options, but the gearing on my 3-speed hub I don't think would be very helpful on its own, well for me at least. There is quit a spread between the 3 gears on hub of my 6-speed model. Does anyone know if, in fact, the 3-speed hubs vary in this case?

Cheers
Wayne

I believe the Brommie 3-speed hub comes in two flavors: BSR (brommie standard range) and BWR (brommie wide range). The BWR has even bigger steps I think.

Perhaps its the wide range hub that I have. Makes sense as it would work well with the two cogs at the crank giving it intermediate speeds within the wider range of that particular hub.

Thanks

Numbers..

BSR is the same as the AW3, has been, .75 and 1.33

BWR is .64 and 1.57. 1:1 is the middle gear , of course..


they used a German Sachs, hub for a while in the Mk3 bikes, their first 3 by 2 _ 6 speed

.0.73 and 1.36..

Both types would have a wider driver, capable of taking 2 cogs , side by side, the Sachs adopted the standard 3 spline cog,
just made a thinner 3/32 13, & a 15t that skipped every 5th tooth as a shift gate..

The Newer hubs adopted a Shimano 9 spline driver and the cogs for those can be a 12, to 16..








.....

Thanks for those numbers.

FWIW , with my BSR, I changed the pulleys to nylon Tacx, with a sealed cartridge bearing, because I could.

they are a bit quieter as the chain passes over them ..

since the ones on the 6 speed are integral to the way the shifter works .. they are what they are.

Just to help clarify things;the 3spd Brompton uses the BSR hub,the 6spd uses the BWR.

If I ran the zoo,they'd both use the BWR,for both the extra range and the ability to easily convert a 3spd into a 6spd.

if i ran the zoo, the BWR would be in wide distribution and available at every LBS. i run one on a little mini velo bike and it's damned brilliant. i would readily pop one on my BF classic diamond frame commuter.

http://i.imgur.com/TkOJGQn.jpg

Hmm... I've been riding a 3 speed recently and a 33% jump from gear 2 to 3 is frequently uncomfortable (1 to 2 is fine); on another website someone (possibly a regular here also) referred to the change into 3rd as like 'hitting a brick wall'. A 56% jump must result in a completely ridiculous cadence change, from cartoon hamster to dinosaur, instantaneously.

oh ye of little imagination... if you can't possibly see how these ratios can be applicable to a commuting situation, then don't buy one. easy

http://i.imgur.com/0pEb5ZF.jpg

That's aout right. Its not ideal. One reason the 5 speed was used instead. But if a butterfly flaps it wings in pbrazil the 5 speed goes out of alignment. 8 speed had limited shifter compactability and tends to lose gears if you buy the wrong vintage.
3 speed sa hubs were ok last cenerty on preiuim quality bikes. Yes they are reliabable but mostcyclists expect more. I bought a cargo bike with a three speed on and that was just about ok once I down geared it. I should have paid more for the eight speed nexus version.

I believe Brompton choose it's current 6 speed configuration when it could not source the 5 speed due to Sturmey Archer's demise. Now that the 5 speed is back, they should drop the six speed altogether.

I go along with that. I'm not knocking Brompton by any means. But a 5-speed hub would work out better. With the 6 speed model, I find myself going back and forth with the left and right shifters to get the appropriate gear. All gears in one hub would definitely make for better and smoother shifting. But, I am OK with the present layout. It just took a little time to acquaint myself with it that's all. Now its sorta like second nature when shifting. All in all, I just LOVE my Brommie. The best bike I have ever owned.

current 5 speed is single cable , at it's core its the AW/BSR 3/4 , 4/3 gear, and another set of planetaria
gears for 1st & 5th..

Sach's 3 speed was the source of re-designing the extended driver to fit a 13 & 15 t 3 spline cog ..

Iv'e been using the 15t which has 3 short shift gate teeth and is 3/32" thick, on my BSR..
3/32 chain


FWIW
the old 5speed used 2 pull chains the 234 ratios a little tighter spaced ,
but those are said to have some quirks ... gear slipping, mis shifts..

now the SA 5 speed is using the 9 spline driver same as the BWR, and cassette freehubs , sorta,
and 2 cog fittings are posible SunRace SA
given12,13-15, 16 t .. as Brompton spares 13-15 from the BWR
the 12 - 16 pair coming from the 2 speed non IGH hub kit.

some bigger ones from te S3X hubs, also 9 spline..

Some machine shop access needed, but says here... you can fit 3 cogs on and run 10 speed chain spacing.
http://forum.ctc.org.uk/viewtopic.php?f=5&t=55908

My 5 speed is slipping in 2nd. What are they like to sort out. I changed a sash dualdrive internals once , but that's about my knowleage limits. Local bike shop charhge about £25 so I will proberly go with that.
I don't like the 6 speed either for the reason you mention, proberly ok if you use it all the time , but I tend to grab nearest bike or whatever takes my fancy.
However, the 6 speed is the brommie option to go for in the current range. Big jumps in the 3 speed drives me nuts.

My biggest issue with the BSR is not the jumps in gearing, it's that the gearing is way too high for me. I like to spin or at least approach it on most bikes, so when I hop on the brommie, no spinning that day. I rarely change out of the smallest gear. Time for a much smaller chainring, the S/A X-RF8 (8-speed) hub retrofit, or both.

The old standard ratio 5 speed hubs are weird, they can run really nicely periodically and feel like cheese graters periodically, for no apparent reason. The same goes for the effect of the Brompton chain tensioner on the drivetrain, which seems to align slightly differently every time the bike is unfolded. Put those two together and you have a bike that sometimes feels great and sometimes feels dreadful.
Having ridden the Brompton as a 3 speed for a few weeks I've now switched back to the 5 and for the first time used a 14t sprocket rather than a 13t. First ride was great, super-smooth. I have a feeling that the Brompton chain tensioner works much better with a larger sprocket so fingers crossed things will be a little smoother from now on.

Based on all that I can see the logic of an efficient 3 speed hub plus double sprocket... however, it may be wrong to assume that the BWR is as efficient as an AW since it has very small planet pinions with a low tooth-count and a big-ass sun. I've heard the tooth profiles are better machined than on former models and no doubt they have to be to mitigate the inefficiency of the inter-meshing of big sun and small planets. But that was probably the biggest problem with the old 5 speeds: the crude box-shaped tooth profiles. So perhaps the new 5 speeds are a fair bit smooth in operation, and perhaps a 10 speed with 14t and 16t sprockets would be very nice.

If I'm right about any of that then the BWR ought to feel most 'toothy' in 2nd gear, is that the case?

Brompton gears table is here

http://support.brompton.com/entries/...es-and-ratios-

The standard 3 speed gears are roughly the 3rd, 4th and 5th gears of the standard 6 speed gears.

Bigger , say a 15t cog is what I use, and as you say fit a smaller chainring ..
they make a 44t,& of course you can always fit a crank from some one else..

even set up a double.. not to mention the new Spider crank, also offering 44,50&54t chainrings

but now any 130 bcd ring can be fitted on those cranks..

where the others previously, were a swaged together arm and chain ring, set.


is that the direct 1:1 cog driving the hub-shell gear to you counting system?

Or the larger 15t cog on the outside and high gear in the hub?

I mean 2nd from lowest (small sprocket, low hub gear).

I seem to recall reading is was to save weight;the 3spd hub + 2spd der setup is much lighter than the 5spd hub.

No, not at all. Actually last time I looked at the SA website the 3 speeds seemed to be heavier than a couple of years ago, so there's no difference between 3 and 5 speeds. The 5 speed hub is a very concise design.

5spd hubs w/out brakes on SA's site are listed as around 1060-1230g. My Brompton catalog says the 6spd is +920g. I'm guessing SA is just giving the hub and not the shifter/cable,and that Brompton is giving the whole hub/der/shifters/cables setup,so from that it sounds like you're saving prolly like a 1/4 lbs with the 6spd system.

It's 1060g for the 148mm version, the appropriate size for a Brompton. That's 40g heavier than the 3 speed hub.
The Brompton bike builder states that a 6 speed is 180g heavier than a 3 speed. So the 5 is 140g lighter.

what's your point?

do you have links or citations for any of this? in fact, does anyone in this thread have any stats or documents they can link to?

to my count, there are at least 5 different hubs mentioned in this thread with all sorts of stats glibly thrown about.