The tread on some types of tires can be hand cut to increase the size of the existing grooves. Hand-cutting is useful for improving adherence in certain intermediate situations, between dry and thoroughly wet surfaces, or on mixed gravel/rock and sandy surfaces.
The tread efficiency in the conditions for which it was originally designed will no longer be the same. Hand-cutting must be carried out by experts using specialised equipment, suitable for use while observing safety regulations.
THE COLOUR RED IS USED TO HIGHLIGHT WHERE GROOVES CAN BE HAND-CUT