A flat tire is never a fun discovery, but often the tire can be repaired. The following are the factors that impact the decision on whether to repair or replace the tire.
1. Puncture Location
Punctures are usually small and caused by sharp objects like nails. They can often be repaired using a plug and seal method, but only if they are located on the main tread area of the tire. Punctures in the sidewall or on the shoulder, which is where the sidewall meets the tread, can't be repaired safely via plugging. When punctures are in these locations, replacing the tire is the only good option.
2. Cut Severity
Cuts are more damaging than punctures. A cut less than a quarter-inch long can sometimes be repaired, but larger cuts typically mean a new tire is needed. Location matters just as much as it does with punctures -- repairable cuts can only be on the tread area of the tire. Further, the cut cannot sever any of the steel belts that reinforce a tire.
3. Sidewall Damage
Any damage to the sidewall means that a tire needs to be replaced right away. This damage includes that from the aforementioned cuts and punctures, as well as damage like bulging and warping. The issue is that a damaged sidewall is under a lot of stress when you drive, and any damage increases the chances of a dangerous blowout, especially when you are driving at higher speeds.
4. Low Tread
Sometimes the damage is repairable but simply not worth the effort. This is the case when the tire tread is low. Low tread means that the tire has reached the end of its working life. It is now more susceptible to problems like punctures or flats simply because the rubber is so worn down. You can check tread by slipping a US penny in between the tread head first. If the top of Lincoln's head is visible, then the tread is too low, and replacing it is the safest option.
5. Multiple Punctures
A single puncture in the tread is usually repairable. Two punctures can also be repairable if they are on opposite sides of the tire and both lie within the treaded section. If there are more than two punctures, multiple types of damage, or punctures that are closely spaced, then you can't have your car repaired with any guarantee of safety, so it is better to get a new tire.
Contact a tire repair service if you have a flat tire that needs to be assessed for repair or replacement.