Cycling UK Forum

I have just been given a road bike and having adjusted seat, bars n brake levers its almost good to go.
Decided to put mudguards on it only to find the recessed allen nut, for the rear brake, has had the hex section rounded out.
So how do I get the rear brake off?

list as I would try it
1. try a new Allan key.
2 try tapping the hex key in
3. try next size up
4.if there is enough of the Alln key proud of the frame grip with mole grips
5. find something to wedge in the hole an old scredriver or such like

Sacrificial Torx bit. Easy enough to buy, even from Poundland.

as above, or

- remove the rear wheel, disconnect the brake cable, swing the caliper ACW to unscrew it. You may find that you have some flats on the brake, near where the spring mounts; you can often use a cone spanner here to help things along. Or...

- have someone weld something onto the rounded allen nut using MIG welding.

The caliper swinging thing often works very well, and once the caliper is a bit loose, everything comes strangely free all at once.

cheers

Caliper swinging thing didn't work.

Are you saying that you could swing it, or turn it through 360 and keep going?
If you are turning and turning and turning, at least the frame portion is free.
This is good!

Next task is to grip the nut.
Torx idea is good or at least a new and good quality hex key.

If neither work, you are into the realms of a workshop and an engineering solution.

When turning caliper the nut spun with it and the allen key had only been used on front caliper since Santa dumped them under the tree!

In the past I've used a dremel-alike (mine was from Aldi) with an abrasive bit to grind a slot (on the grounds that it is the easiest shape to get right enough) in a damaged fixing head so I can get a screwdriver or a flat blade bit on a ratchet driver on to release things.

Rick.

I have the same dremel-esque kit but have ran out of the little grinding discs, so ebay here I come.

if the nut spins too it is seized on the thread but there must be some leeway for a bit of cunning;

I'd suggest that if you can get a suitable bolster behind (on the nut) and a hammer on the other side then a bit of gentle lengthwise tapping may persuade the nut of the error of its ways. You need a bolster that is about twice the weight of the hammer head.

BTW it is worth checking that you didn't get a substandard 5mm bit from Santa, or indeed that you didn't pick up a 3/16" one by accident; it is easily done; best check with vernier calipers.

cheers

Another way round this is to disassemble the calliper on the bike, making a careful note of where the parts go then you can attack the stubborn allen key and buy another one if it is beyond rescue.

Probably too simple, but still worth asking - have you drenched everything in plus gas or wd40 and left it to soak overnight before trying the wiggly stuff?