Author Topic: Brompton stem $#@%ing stuck  (Read 1895 times)


  • Cat 6 Racer
Brompton stem $#@%ing stuck
« on: October 10, 2010, 08:26:59 pm »
I've removed the bolt, sprayed it with penetrating oil and tried gentle persuasion with a screwdriver and hammer, but the stem remains stuck fast.

Any suggestions?


Re: Brompton stem $#@%ing stuck
« Reply #1 on: October 11, 2010, 06:41:14 am »
Yes.  It's an expander rather than a wedge, and expanders are the work of Stan.

You have to loosen the bolt a few turns, get a hammer and punch and hit the bolt Very Hard until it drops.
Never tell me the odds.


  • Cat 6 Racer
Re: Brompton stem $#@%ing stuck
« Reply #2 on: October 11, 2010, 10:28:51 am »
It's an expander rather than a wedge

Ah. That explains it. I fear I may have been too reticent with my hammer-based persuasion technique. I shan't be so shy when I have another go tonight.


Re: Brompton stem $#@%ing stuck
« Reply #3 on: January 04, 2020, 12:47:46 pm »
Releasing a stuck Brompton Stem – a solution!!
•   Loosen the stem bolt  by using an allen key to undo the bolt by 4 or 5 turns
•   Cover the bolt head with a piece of wood and whack it hard to drive the bolt down and release the wedge from the bottom of the stem.
•   Remove the front wheel, the front mudguard and the front brake assembly.  Let them hang loose without stretching the brake or lighting cables.  Secure with PVC tape if necessary.
•   Unscrew the bolt and remove. (This is not required if the stem rotates and can be removed in the normal way).
•   Using a long screwdriver or a suitable drift, drive the wedge out of the bottom of the header tube.  The wedge will be a tight fit at the bottom of the tube and you will need to drive it slowly.
•   Secure the bike upside down, say in a Workmate or similar.
•   Now you need a socket that is a tight fit to the inside of the bottom of the header tube.  The best choice seems to be a 16mm plug socket.  A standard (shorter) socket will do but the added length of the plug socket seems to help.  If you don’t have metric sockets, 5/8” imperial sockets are good as well.
•   Now insert a 150mm (6”) extension bar on to the socket.
•   Snug the socket into the bottom of the header tube and allow it to rest on the bottom of the stem.  A few goes with penetrating oil on to the bottom of the stem before this will be helpful.
•   With the extension bar protruding out of the bottom of the header tube, give the end of the bar some sharp whacks with a standard claw hammer.
•   Surprisingly the stem will start to move after a few whacks.  As the stem emerges it will drop down at increasing speed.  Take care as you get to the end of the stem otherwise you will end up driving the socket into the end of the stem.
•   Remove everything and clean up.
•   Use a 38mm spanner to remove the headset, clean and grease.
•   Reassemble, grease the stem tube before reinserting it.  You will probably need a few hammer taps on a wooden block to reinsert the stem.
•   Reassemble brake, mudguard and wheel.


  • Whimsy Rider
Re: Brompton stem $#@%ing stuck
« Reply #4 on: January 04, 2020, 09:03:09 pm »
Should be a 36mm headset spanner. The rest is a bit of a drag though...
Wheel meet again, don't know where, don't know when...

Re: Brompton stem $#@%ing stuck
« Reply #5 on: January 05, 2020, 11:26:38 am »
It is possible for steel stems to stay stuck even after the wedge or expander has dropped.  I had a Kona Hahanna, bought as a project, where I never got the stem out.  I tried all sorts of penetrants, as much heat as I dared without cooking the paint, a lot of leverage (broom handle through the stem and 2 x 4 through the fork crown) but nothing shifted it.  Oxy-acetylene would have done it, no doubt, at the cost of a respray.
Never tell me the odds.