It's possible that you will notice some debris next to your Brompton (or maybe you won't notice!)
We made the below video to highlight them!
Don't panic (there's no need to carry a towel)
So here are our top 5 items that can fall off of your Brompton!
5/ Seatpost bung
The seatpost bung lives at the bottom of the seatpost
It just pushes in (and is held in by friction - no glue as standard)
The Brompton seat post bungs' purpose in life is two fold:
- To stop the seatpost (metal part) from crashing into the ground when the seatpost is lowered - which (we found in the past) can damage floor tiles
- To act as a brake - the rubber stops the bike rolling around - especially on trains when they are moving and the bike is parked
Note: The G Line is designed in such a way that the bung doesn't reach the ground - it hits the suspension block - but it can still fall out
All model Bromptons (with exception of the superlight carbon seatpost used on the T Line) use the same seatpost bung
Will your bike function OK without it? Yes
We get a lot into the shop where the seatpost bung is missing - we put one in to save our tile floors from damage!
Having no seatpost bung isn't actually going to stop your Brompton from functioning properly
4/ Chain catcher
This device was launched with the advance rear frame initially used on the T Line and P Line ranges of bikes
With the new C Line 4-speed and 12-speed launched in 2025 this is now standard (although there are different versions depending upon the model) on all Brompton folding bikes - including the G Line and Brompton Electric 4-speed e-Motiq range
Basically if you have a Brompton 4-speed, 12-speed or 8-speed (G Line with Shimano hub) then you will have a chain catcher
It helps prevent the chain falling off of the front chainring when folding the bike (we found this to happen most when transporting our G Line - with a missing chain catcher - on its side in the back of the car)
It's held on with strong double sided tape
It doesn't stick so well to the G Line due to the textured paint finish
The bike will work perfectly well with it - but the chain is slightly more likely to fall off when the Brompton is folded
If you notice it has come off and you found it ... clean up the frame thoroughly, remove any residue of the tape for the chain catcher itself and then re-affix using good quality double sided tape
It fell off
If you are lucky you may find the chain catcher on the ground so you can pick it up and re-fit it
It's gone
If you are less lucky - you may just notice a mess where the tape was holding it in place
How it should be
This is how it should look - in this case on a Brompton C Line Electric
3/ Cable anchor / gear indicator chain
The cable anchor (which connects to the hub gear cable) and gear indicator chain are used on Brompton folding bikes with Sturmey Archer hub gears
Note: different gear indicator chains are used for different Sturmey Archer hubs
They can come loose - they are only done up finger tight
If they disconnect - the first symptom will be that you can't change gear
If left disconnected the gear indicator chain can work loose and fall out completely or the knurled nut from the cable anchor can fall off - making reconnection ... difficult without getting new parts
The solution is to check regularly that they are connected to each other
Gear indicator chain
On Brompton bikes with Sturmey Archer hub gears this is very important - it is used to switch between gears - without it there is no hub gear changing possibility!
2/ Viz saddle mounted rear light
The Viz saddle mounted rear light is a great idea
It fits with a special mount (included the Brompton saddle mount light kit) which connects to a Brompton saddle (not non-Brompton saddles)
It just clips in
BUT
It's quite easy to knock off too by mistake
(Personally we use lights which connect to the saddle rails rather than the saddle itself - and are harder to remove - so don't fall of easily)
Now you see it
The saddle mount is a great idea - it means you can pretty much keep the light on the bike
When you lower the seatpost for folding it doesn't interfere
Now you don't
But it's relatively easy to knock off either when putting your leg over to get on the bike
Or knocking off with your hand when dropping the seatpost
Our alternative
We use the Fidlock pin clip saddle mount
Combined with a Fidlock action cam mount
And have an adapter to allow mounting of a Varia radar light
1/ Frame protector
Introduced with the P Line and advance frame was a nice metallic looking frame protector - to stop the front hook from scratching the rear triangle
For a while this protector was even available as an aftermarket item from Brompton
It's a question asked a lot on the /brompton subreddit on Reddit - "what's this bit that fell off of my new Brompton?"
When Brompton stopped selling them as an after market item they said it was only actually designed for shipping and should be removed during the PDI (Pre Delivery Inspection) prior to handing over to the customer
It's only held on with tacky glue - so comes off easily
If you want to re-attach it we suggest good quality double sided tape
This is how it should look when fixed to the bike!
Other honourable mentions
Bonus ... the rider - we hope that doesn't actually happen too often!
Lower stop disc
Chainring guard - this actually used to be quite common with the older fixed crankset but has been fixed by the newer spider crankset