Any puncture or injury to a tire's tread area obviously affects performance and safety. Proper repair is critical. The puncture must be repaired on both the inside and the outside of the tire. One reason is the differences in the air retention abilities of the different layers of rubber used in a tire's construction. The thin layer of rubber on the inside of a tire is halobutyl rubber, which is designed to hold air. While the tread area is thick and durable, it is designed primarily for traction. Since all parts of a tire are engineered to function as a single unit, any repair must take that into consideration.
A tire patch must be firmly adhered to the inner liner. If a patch is not used or is incorrectly applied, air under pressure can leak through the puncture into the body of the tire causing separation. Also a plug must fill the injury or puncture and seal the tread surface. Winter driving is especially corrosive. If road salt, debris or moisture penetrates a tire, rust in the steel belts can result, leading to separation. Therefore, a plug must be in place to seal the tire from the outside as well.
Nails and other objects may protrude into a tire causing internal damage that is not visible or apparent from the outside. A tire repair can be properly made only if the tire is removed from the rim, a thorough internal inspection is carried out, and repair is made from the inside out.