The new brake cable ends which I have bought recently have required modifying before fitting.

The slot machined in the outer sleeve of the cable end is the wrong shape and cuts into the "neck" of the brake lever, just beside the ball end, instead of the pull of the cable being transferred to the surface of the ball. The narrow "V" of the slot must be filed to allow the lever ball to move to the end of the sleeve and bear fully on the inner end of the sleeve. Do not make the slot too wide so that the ball can pop out. In the case of the front brakes, the slot must be lengthened far enough to keep proper contact on the ball at all steering angles.

If the shape of the slot is not corrected, the sleeve cuts into the neck of the brake lever. You will often find damaged levers for sale at autojumbles.
There is another problem if the new cable ends are fitted to "pre-Girling" front brakes with short levers. The cable end is more bulky than the original fitting and catches on the back plate on full lock; near side on right lock and off side on left lock. The solution is to file away the end of the sleeve at the point nearest the back plate, sufficient to avoid contact. Again, check all steering angles.

When the cable end makes contact with the back plate, it prevents the cable end following the line of the cable; this puts a kink in the cable, strains the brake lever and may cause the brake to stick on.

Dave Fulton Solent A7C with thanks