Would be safe to drive my mountain bike with little cracks on the tire?please help I will used it for university. Do I have to replace my tires?
A tire gets its strength from the cloth casing (“carcass”). The rubber tread is mainly there for grip and durability. It also provides some puncture protection.
Cracks in the rubber usually form due to age (+exposure to the elements) and/or insufficient tire pressure.
My main concern would be that if the rubber is old and hard your grip will be worse, especially on wet surfaces.