Although the preferred method of handling damage to a radial tire's sidewall or tread is replacement of the tire and not a car tire repair, not everyone can afford the price. For example, a low-cost National may cost about $110 with mounting and balancing, while a simple car tire repair will be about one-sixth that cost (about $20), depending on the placement of the repair and its depth.
The way to determine whether an auto tire is repairable is to have it dismounted from its wheel and to shine a very white light on the interior. If the tear is parallel to the tire radial sidewall belts, you will be able to repair it, because the belt material is in good condition. If the cut is perpendicular (across the sidewall material), it's been weakened and the tire must be replaced and wheel repair should not be attempted.
Cut Must Be Clean
The same is true of the tire tread. If your tire has taken a nail cleanly through the intersection of couple of belts, you'll be able to repair the tire. However, if the radial tire cord itself has been damaged, the tire should be replaced. You can tell that this has happened if the nail or spike goes in at an angle and continues across the tire.
To properly repair a radial tire's sidewall will cost between $20 and $30. It will involve preparing the area around the cut or slice–the area to be patched–with a vulcanizing compound and letting it dry. Once dry, it is sanded to roughen it up so it creates a surface area that seems larger than it is to the next layer of galvanizing glue and the patch you lay over it. Once this is completed and dried, you cover the entire area with another layer of galvanizing material as added strengthening.
Clean and Dress outside Area
On the outside, you simply make sure the area is cleaned and dress it with the galvanizing glue. When it has dried, you take a small piece of patch material, already covered in galvanizing glue, and you place it over the cut and let it dry.
A tire patch involves a two-step process: first you enlarge the hole in the tread with an awl and then you apply galvanizing glue to this area. When this is finished, you take plug material, carefully inserting it into the awl you used to enlarge the hole, and you insert the plug material into the hole in the tread, ensuring that the plug is well treated with galvanizing material. You must then ensure the plug has good contact the tire tread. Next apply an internal patch by covering the plug with galvanizing material and then applying a piece of patch material to the plug. Wait until it's dry and then remount it on its wheel, size the tire and refill it. This should cost about $20.