Fraying disc brake cables

I’ve just renewed my front brake cable – again! Both the Shimano disc brakes on this bike eat cables. They keep on fraying at the point where the cable is clamped to the actuating arm. As you can see, the cable lifts off the curved cam and bends sharply at the clamp, eventually failing.

Mike Benjamin

The arm needs to be re-positioned so the cable remains on the cam. Un-clamp the cable so the arm returns to its resting position – a lot further clockwise than it goes now – and screw in any ‘barrel adjusters’, e.g. on the levers.

n Slightly loosen the two bolts securing the calliper to its bracket (at right-angles to the similar bolts of which you can see one head in the photo) and slide the whole calliper inwards towards the disc, until the outboard brake pad (to which the arm is connected) clears it by less than half a millimetre. Re-tighten those bolts.

The other (fixed) pad will now have to be adjusted in toward the disc, by turning the screw behind it with an allen key poked between spokes, until that pad also clears by less than 0.5 mm. Re-secure the cable and all should be well.

Some cable discs (Avid BB7) have a means of adjusting the movable pad relative to the actuating arm. Most don’t. Any large adjustment, greater than can be made on the levers, must NOT be made by clamping the cable shorter, but by shifting the whole calliper. Expect to do this when new pads are fitted and when they’re part worn, so as to keep the cable on the cam throughout the operating stroke of the brake.

Chris Juden


This was first published in the August / September 2014 edition of Cycle magazine.