On dry surfaces, tread is unnecessary because it actually decreases the amount of tyre surface area on the road (making it slightly less safer). However in wet conditions, the gaps in the tread serve to channel water away from the centreline of the tyre and even completely out of its path. This allows the tyre to contact the ground rather than hydroplaning on top of the water, and so it can both accelerate and brake more effectively.
They are not only important for wet conditions. People tend to lose control on wet surfaces because the water acts as a lubricant, causing the wheel to slide more easily. A tire with 'better' tread will slide less than a tire with 'worse' tread.
To grip the road surface. You need tread especially in wet conditions.
The normal racing tyres are slick and have no tread. The intermediate tyre has a 2.5mm tread, and the full wet has a 5mm tread.
Its so tyres have grip in the wet
For traction and to prevent hydroplaning on a wet road.
Loss of traction poor tread depth on tires
good trac on dry bad on wet
Slick tyres are tyres without tread. The tread is only there so that water can be pushed into it on a wet track. On a dry track no tread is needed and therefore you will get more contact with the road without it, allowing the cars to accelerate/brake/corner faster. Therefore slick tyres are used as they are faster in dry conditions.
Tires need replacing. 2/32nds is the minimum tread depth for a tire to be safely used. In most statesin the USA it is a law, can get ticketed. Tire tread that low compromises braking handling in wet and snowy conditions.
Tires are one of the most important features on any vehicle for which your safety depends. Features that you want to look for in a good tire include tread depth and tread wear, short stopping distance and wet weather traction. Some great tire brands include Goodyear and Mavis.
Increases grip if there is water on the roadway the water can enter the holes in the tread and not interfere as much with the rubber contact with the road.
Quite a bit especially if your tires are worn down to or below the tread depth limit.