Question in subject line. Thanks! JP

The answer is..probably if your Brommie uses 3/32" derailleur-type chains, but it appears some 3-speeds use 1/8”. I suspect you wouldn't be asking if you didn't already have the chain handy, so might as well throw it on there and see what happens. Good luck!

https://www.bikebrompton.com/accesorios.aspx?Id=chains

I'm pretty sure I need 3/32 chain for the Brompton. Problem is I can't find the width for SRAM PC-971 chain anywhere.

Any multi-speed chain should work as long as the cogs can accept 3/32" chains. Multi-speed chains are 3/32" inside spacing, only the outside width changes.

You may need to adjust the chain pusher end-stop screws slightly to compensate for the narrower chain.

I have found the cheaper chains work best for me. By that I mean KMC and SRAM 7-8 speed chains.I used a higher end chain designed for 9-10 speeds which did not sit all the way down on the rear cogs although the chain ring was fine. Kept clean and lubed they last quite a while, at least here in the high desert.

The SRAM PC-971 is a 9 speed chain so it should have a width between 6.6-6.8 mm. It is a 3/32" chain so it should work with your 3-speed Brompton.

No. ... but you could Measure it..


Now you can order S-A replacement cogs in 3 or 4/32, Brompton Stock is 1/8.

years ago Sachs of Germany made the 1st 3 by 2 hubs for Brompton UK . those were thinner, 13t and a 15t, that skipped every 4th tooth

so had (spares are still stocked) 3 incomplete teeth to help it shift between the 2 cogs.





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I've been using a full bushing 3/32" chain* .. the type is longer wearing than Derailleur chains.. On a skip tooth 15t, 12 full teeth, 3 short ..

* it was an OldStock find, from Harris Cycles, in Newton MA..




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Looks like 3-speed Bromptons may come with 1/8" cogs after looking at SJS's website. Best off to measure your cog to see if it 1/8" or 3/32" as already suggested.

Mine came with a 3/32. it is, however,at least 3 years old. I don't know how to tell how old they are, perhaps from the SN or some such? It could have sat around the bike store for years. it was originally a single speed.

Just put the chain on and you will know instantly if you are going to need a 1/8" chain. The 3/32 will not sit down on the cog if you need a 1/8".

Newer Brompton come with 3/32" chains, but I think pre-2012 or something 1 and 3-spds were standard 1/8", while 2 and 6-spds were 3/32".