How to Fix a Flat Tire
Flat tires are a sad fact of life, and like death and taxes, they simply cannot be avoided. No amount of tire rotation is going to prevent it. However, unlike death and taxes about which nothing can be done, it is sometimes possible to repair flat tires, but be aware that there is right way, and a wrong way to go about it. The image below shows the WRONG way fix a flat tire; this particular repair means that the tire’s speed rating may no longer be valid, because there is no telling to what extent the steel belts have been damaged by the object that punctured the tire.
Nonetheless, this type of repair does have its uses, but only as an emergency stop-gap measure until the tire can be inspected and either repaired professionally, or replaced if the injury is too severe to repair safely. Tire repair is a life-and-limb affair, and simply plugging a hole in the tread can cause unexpected tire failure, and a potentially fatal crash. So, what is the right way to fix a flat tire? Read on, and we will tell you what you need to know about.
The right way to fix a flat tire
Before we start, a word of caution; any repair that does not involve dismounting the tire from the rim must be considered improper, and by implication unsafe. What might look like a simple puncture may have been caused by an object that was long enough to damage the inner sidewall. Failing to inspect the inside of the tire for damage, especially when buying used tires, could mean that an unsafe tire is placed back in service, so ALWAYS dismount the tire from the rim to check for internal damage BEFORE attempting any type of tire repair.
Even though the repair in the centre is considered to be the only safe way to repair a puncture, most, if not all, tire manufacturers recommend that only punctures smaller than ¼-inch in diameter be repaired. Larger punctures and perforations on the shoulders and/or sidewalls of tires should not be “repaired” under any circumstances, since no repair can restore the original structural strength and integrity of these parts of a tire. So why is the repair in the middle the only right way? Read on, and we’ll explain the issues.
The “repair” on the left explained
The inner linings of modern tires are designed to retain the air in the tire, and while the patch over the puncture site might restore the lining’s ability to perform its function, the repair does not seal the path of the puncture through the tire tread.
Failing to seal the path of the puncture can (and does) cause water to penetrate into the layers above and below the steel belts, where said water eventually causes corrosion of the belts. In time, this corrosion can spread to a large area surrounding the puncture site to cause bulging, or separation of the steel belt from the rubber compound around the area of the puncture site.
Such a tire is dangerous, but the trouble is that you don’t know it is dangerous because the damage caused by corrosion of the steel belts often does not become apparent until the tire fails. Again, don’t buy used tires because you could end up with such lemon, especially when there’s plenty of cheap tires available for sale.
The “repair” on the right explained
In this case, the path of the puncture is sealed with a string plug, but there is no guarantee that the seal extends to the inner liner. Ergo, there is no guarantee that air will not leak into the tread layers above and below the steel belts.
When this happens, which is often, the tire bulges or in the extreme cases, the tread can separate from the casing. Such a tire is obviously also dangerous, but an additional problem is the fact that tread separation can happen suddenly, with an equally sudden blowout as a result.
Why some tire repairs fail
Three things MUST be considered when a tire is repaired, so let us briefly look at each;
- The damage caused by the perforation must be evaluated, and weighed against the possibility that the tire might not be safe to use after the repair. Sadly, there are many resources on the internet that describe the process of plugging punctures with string plugs, but precious few that describe the possible dangers of not dismounting the tire to check for internal damage. String plugs should only be used in an emergency, and then only until the tire can be inspected professionally. Anything else is potentially dangerous, and should therefore be avoided.
- The seal must restore the tire linings’ ability to retain the air inside the tire. While both string plugs and inner patches have their (limited) uses, the only reliable way to fix a puncture is by using a combined patch/plug to seal both the lining, and the path of the puncture. However, even this method has limitations, and it should only be used if it is certain that there is no secondary damage to the tire casing or reinforcing steel belts.
- The tires’ speed rating must be considered. While it is possible to successfully repair the tires used on family sedans, it might not be advisable to perform any sort of repair on the tires of Lamborghinis, Ferraris, or for that matter, any other supercar. The tires on these cars are subjected to extreme loads and strains, which means that a tire repair that works on say, a Mazda 3, may cause a catastrophic tire failure on the Lamborghini when the stresses caused by high speed driving overcome the repairs’ ability to seal the puncture site. Therefore, punctured tires on high-performance cars should ideally never be repaired to avoid the possibility of a repair causing tire failure under high load conditions.
One more thing
As stated before, tire repair is a life-and-limb affair, so do NOT attempt any type of tire repair if you are uncertain if the tire can be repaired or not. In these cases, the better option is always to have the tire inspected professionally, or replaced to avoid the real possibility of experiencing problems and issues with the repair at an inopportune moment, such as during bumper-to-bumper rush hour traffic on your way to work.