Before fixing a slow puncture, it is important to determine the source of where the air is leaking on the tyre. Slow punctures are most commonly caused from pinholes or very small punctures, previously repaired punctures, bead leaks, faulty or worn valves or even tyre and/or wheel defects. We have explained each possible cause in detail and provided the recommended self-diagnosis and resolution.
Before we get into the detail of each plausible cause. First and foremost, always take your vehicle with the problematic tyre to your local tyre service centre for professional inspection and advice.
The list below is in descending order of common causes for slow tyre punctures.
Pinholes and small punctures
The most common and generally the most frustrating to resolve, are the tiny pinhole punctures. Air will leak so slowly that it is often unrecognisable by submerging the wheel and tyre into water.
The frustrating part of the ordeal is if the puncture is in the sidewall of the tyre. Safety regulation states that no tyre may be fixed with sidewall damage of any kind, (you can imagine the despair if this is a new tyre). No upstanding tyre centre will repair a puncture on the sidewall, regardless of diameter. A sidewall falls out of the legal area of where a tyre can be repaired. A repair of such nature condemns the repairer to legal action if an accident were to happen due to a tyre fault. Read our article on why sidewall punctures can not be repaired – here.
You can however take the risk and repair it at your own peril. A combination of tyre sealant and a gator or mushroom plug may provide a fix.
Picture of legal repair area.
Previously repaired punctures
A previously repaired puncture may often leak air very slowly. This is most common with external repairs which are done with repair strings and a rasping tool. The repair string may or may not provide a complete air seal. A simple, yet very effective method that is regarded world wide by bodies of tyre associations as a temporary repair.
If there is air leaking from a previously plugged puncture, the best option is to have it fixed professionally by inserting a mushroom plug and then patched from the inside.
A bead leak occurs when the air escapes from the area where the tyre meets the rim/wheel. This is caused from either the rim not being round (rim is dented or damaged), the tyre is damaged or the tyre and rim are not of the same size or compatible for one another.
Your only resolution is to have the wheel repaired or the tyre replaced.
Faulty or worn/torn valves
Most common with older tyres, the air escapes from where the valve joins the tyre. Again this is a difficult repair as the valve stem may need to be replaced. A vulcanising paste or cement can be used in combination with a patch. As the tyre is likely to be too old for legal use, or worn beyond legal limit, consider replacing.
Tyre and wheel defects
There are varying qualities of tyres and wheels on the market, even imitations. Lower quality tyres have low density rubber compositions that lead to higher rates of porosity leaks. Not only will the tyre lose it’s pressure faster but may also degrade and oxidise at a higher rate than a premium brand.
Lower quality wheel’s and rims are manufactured with lower cost materials and therefore are more susceptible to faults, such as not being 100% round or does not provide a suitable air tight seal. Any small pothole could disrupt the seating of the tyre on the rim.
At the end of the day, it always pays to consult a professional tyre centre and buy reputable branded products.