Fitting ‘proper’ mudguards – those that have steel stays and brackets that attach to the brake bolts – was made a lot trickier when the recessed ‘top hat’ brake nut became the norm. While they look neat, these little beasts remove the old-school option of trapping the mudguard bracket between the nut and the brake bridge or the rear of the fork crown.

Some high-end steel frames have a small M4 female thread on the underside of the bridge or crown. A short screw going through the guard into the thread does away with the need for the bracket. Otherwise, mechanics usually opt to place the bracket between the brake caliper and bridge or crown, which places it where clearance is at a premium and, in the case of the front ‘guard, shifts the arc forwards leaving a bigger unshielded section of tyre in front of the feet.

There is an alternative, which allows the mechanic to fit the guards correctly using the brake top hat nuts. They have a 6mm (M6) thread but a 5mm Allen socket. 5mm happens to be the drill size for an M6 thread, so an M6 tap will run straight through the socket without the need to drill it out. Do this from the threaded end so there is only one thread. This leaves the 5mm socket able to accept an Allen key and an M6 threaded bolt.

The nut is easier to stop from turning in the vice if a flat is filed on one side of the flange. Put a nut at each end of the jaws to avoid strain as they are tightened.

Once the nut has been tapped, it can be installed as usual and will take sufficient torque to secure the brake. An M6 screw will then thread into the back of the nut and, provided four or five threads are free, can be tightened enough to hold the ‘guard bracket securely.

This is, of course, best done with a steel top hat nut…

Besides putting the ‘guards in their right place, this modification does make mudguard removal and subsequent refitment a quick and simple process that leaves the brakes untouched.