At some time during the life of your Brompton you may get some wear on the main folding hinge. Getting this repaired at a bike shop or buying the special Brompton reamer (GBP 200) is an expensive business. Here’s the cheap way to do it .
Disclaimer : If you mess this up you could damage your frame which will cost even more money, and also may need to go to your bike shop and explain why you messed it up Attempt this at your own peril!!
Step two : Remove the right hand crank/ chainring and rear wheel.
Step three : Removed the 2x hinge bolts and the rear frame.
These are both installed with loctite so tighten and loosen each bolt in turn several times to break the loctite. If this doesn’t work you’ll have to drill one or both of the bolts out.
Step four : Now it gets interesting. Removed the 2x copper bushes from the frame.
Probably the best way to remove the bushes is to use a 13/32″, 7/16” or M10 tap. You screw the tap into the bush then knock it out from the other side with a drift(in theory). I didn’t have a tap so used an M10 bolt, this didn’t have quite the grip I would of liked so only worked on one side. I used a new bush to measure how far I could screw the bolt in.
Now I was stuck and tried all sorts of other things mentioned online to remove the remaining bush all with little success. In the end I had to make a custom drift that fit exactly through the shaft from the other side of the frame then knocked it through (its a very close fit).
Step five : Install the new bushes.
I used a piece of M6 threaded steel, spacers and nuts to press the bushes into place.
Step six : Reamer the bushes to the correct diameter for the new hinge.
In theory you should use the special Brompton reamer for this but at GBP200 there are cheaper solutions. I get the impression that the official Brompton reamer is in fact a taper reamer which to me seems silly when they know the size of the hinge. You can buy or borrow a 3/8″ reamer which doesn’t do the job perfectly but good enough. Reamer the bushes until the hinge is a snug fit but moves.
Step seven : Grease and install the hinge (make sure no grease gets into the threads).
Step eight : Re-install rear frame and other bits using loctite on the threads. Then fall in love with your Brompton all over again