Which bottom bracket for this Brompton?

[jay clock]

My neighbour has a Brompton and the bottom bracket has given up. Can someone advise what he needs to replace it with? I think I have the relevant tools, but if it looks like the one in the picture can someone advise what tool

do I need for it?

There only appear to be two different models available on the market depending on the year, so if there is a better quality option that someone can recommend please advise because I was assume these Brompton bottom brackets are poor quality

Thanks for your help!

 

[jay clock]

By the way, in case it matters, I think it is a two speed.....

 

[rafiki]

Brompton bottom brackets.

 

[12boy]

I replaced mine whith a shimano UN55. I have the bottom bracket tool so its easy to do. Being a philistine I removed the plastic threaded parts of the FAG bottom bracket that came with it with some vise grips. Your LBS should pull the old one and reinstall the new if you buy the new from them. I used a 118 mm. BTW, the one piece Brompton crank spindle is ISO and the newer ones are JIS. Per Sheldon, ISO cranks will work fine on a JIS spindle, and I've found that so.

 

[jay clock]

Thanks. He does need a new spindle unless he risks the ISO to JIS situation and Sheldon had too many ifs and buts for our liking. Just a practical question, which way do the different sides of the current BB undo?....

 

[Ajax Bay]

I'll take a punt that this chainset needs an ISO square taper. Using a JIS BB is sub-optimal. Get an ISO one. A correct chainline is important.
Differences and compatibility: https://www.sheldonbrown.com/bbtaper.html
Left side normal unscrew. Right side opposite thread.

 

[jay clock]

I'll take a punt that this chainset needs an ISO square taper. Using a JIS BB is sub-optimal. Get an ISO one. A correct chainline is important.
Differences and compatibility: https://www.sheldonbrown.com/bbtaper.html
Left side normal unscrew. Right side opposite thread.

Thanks. Having read Sheldon there are too many ifs and buts so we are going for a new changes it, new chain as that needs replacing and a new bottom bracket with JIS threads. Thanks for the thread advice as well because I can never remember

 

[mitchibob]

Brompton bottom brackets.

You just had to share the page that also has mods for disc brakes ... I'm going to stop looking.

 

[Ajax Bay]

If replacing the chainset is an option then it'd make entire sense to go JIS. The UN-300 has replaced the UN-55 as the lead Shimano square taper BB. Don't know what spindle length the chainset you choose will need but Tweeks have some UN-300s at £15:
https://www.tweekscycles.com/uk/shimano-bb-un300-square-tapered-bottom-bracket-2012876/
and via Amazon @ £14 for a 118 UN-55:
Amazon product ASIN B008YUTWR0View: https://www.amazon.co.uk/Shimano-BBUN55-Square-Bottom-Brackets/dp/B008YUTWR0?th=1&psc=1

 

[Gunk]

My neighbour has a Brompton and the bottom bracket has given up. Can someone advise what he needs to replace it with? I think I have the relevant tools, but if it looks like the one in the picture can someone advise what tool View attachment 563649 View attachment 563650 View attachment 563651 do I need for it?

There only appear to be two different models available on the market depending on the year, so if there is a better quality option that someone can recommend please advise because I was assume these Brompton bottom brackets are poor quality

Thanks for your help!

Shame you're not closer as I have the correct FAG tool to remove it. I know its a retrograde step but personally I would put in an old fashioned BB with loose ball bearings, they run smooth as silk and are much easier to remove, strip and service. The sealed modern BB's are very dubious quality and the Brompton version is crap. However I do have a spare FAG ISO BB which you're welcome to if you want it.

 

[berlinonaut]

Instead of wild guessing I would, as often, simply refer to the technical doumentation that Brompton has been publishing over the years. Not too surprisingly it is a reliable source when working on Bromptons. Unfortunately it seems to be less and less publicly available - I typically refer to my archive that I created in better times, when they were easy to get hold of. Don't know why so many people ignore those documents. The datasheet for the task in question is called ds-crankset.pdf and, among other things, it states:

• In January 2013 a new crankset was introduced with detachable chainrings, this crankset is designed to mount to a JIS taper bottom bracket, it is not compatible with ISO bottom brackets
• We recommend using the ‘fixed chainring’ crankset (pre 2013) with a 119mm ISO bottom bracket spindle, if using ISO cranks with a JIS spindle, tighten to 40Nm
•Crank bolts and pedals should be tightened to 30Nm and chainring bolts to 10Nm; these must be re-checked after approximately 50 miles of riding

So you can use the old cranks with the new bottom bracket. Which is good news as ISO-bottom brackets in the size necessary for the Brompton (68mm x 119mm) are basically close to impossible get hold of for a couple of years already. In JIS Format there are plenty of bottom brackets to choose from. The original from Brompton is available, ok and reasonably cheap. If you want higher quality or less weight you have to invest more (and have again the choice from various price levels).

 

[Ajax Bay]

simply refer to the technical doumentation that Brompton has been publishing over the years. Not too surprisingly it is a reliable source when working on Bromptons. Unfortunately it seems to be less and less publicly available

Which is presumably why people can't find and refer to them. Thank you for the clue which leads with a search to:
http://www.sjscycles.com/Instructions/Brompton/Brompton_Cartridge_Instructions.pdf
Brompton seems to hide its tech docs behind a 'trade account' wall. Helpful.
Edit: Don't think the chainset which the OP's image shows is a 'spider' with detachable chainrings. So maybe the current BB/chainset is pre-2013 and ISO - a 'wild guess' but, hey, this is Hampshire.

 

[Gunk]

If it has detachable chain rings it’s a JIS BB they’re readily available

 

[berlinonaut]

The tech docs used to be freely available on the Brompton web page until they massively redesigned it a couple of years ago. From then on there was a subdomain "trade.brompton.com" in the old design, that offered them. This vanished bit by bit but even today there are still some old links working but you have to kow the URL - so old deeplinks from somewhere in the interweb. For a short period of time Brompton offered in the support section of the new website an article that claimed to contain all the tech docs (which was untrue but it contained a reasonable amount). Gone again, relatively recently.
Brilliant bikes used to offer the according techdoc on each article page for a Brompton spare part. Gone since their recent redesing. SJS used to offer some, but not many in the same way as Brilliantbikes - barely none left.
Today the best bet are older pages of Brompton dealers who know their stuff and some of the country sites as well - some of those offer older catalogues as well. Apart from that some Asian blogs contain some and others can be found on pages like issu.com and alike. It is a total pain in the ass to collect them - took me years but I think my collection is pretty comprehensive. Just that no newly created ones will be added as they do not seem to be published... God knows what Brompton wants to achieve - customer orientation on a technical level has been ripped from their agenda already for years bit by bit and it gets worse every year.

 

[berlinonaut]

Here's a tiny data sheet from the trade.brompton.domain about the issue. https://trade.brompton.com/Uploads/QPart/QPart-Datasheets/ds-bbsp_1.pdf
Not totally comprehensive but with the basic information.

Regarding alternative bottom brackets: In JIS style the best bang for the buck is the Token in 118mm with chromo axle. It is more or less in the price range of the spare part from Brompton but of better quality and less weight. There is a lighter version available as well that uses a ti-axle but is more expensive and harder to get hold of. At SJS you can get the various Ti-parts bottom brackets in a range of weights and prices.
If you want a ISO bottom bracket there is still one available from Specialized TA in two different qualities, the TA axis light, both are not cheap. There should be other ISO brackets available but I am not aware of any.