Car tyres are like balloons. To be at their best they have to be inflated with air. Some tyres have low profiles for performance, others are fatter for comfort and longevity but they all have one thing in common: Like balloons, they can get punctured.
Nails or metal objects accidentally or carelessly dropped on the road can work their way into the rubber, often within the grooves of the tyre, and finally break through to release air.
Sometimes this results in a catastrophic loss of air causing instant deflation; at other times air can seep out slowly and the driver may not be aware until much later that something is wrong, although there are clues. So here’s how to tell if you have a slow puncture.
What is a slow puncture?
Slow punctures creep up on you. Everything feels alright until the driver notices the car is handling a little oddly or gets out of the vehicle and notices a tyre is clearly soft. A slow puncture is one that causes air to be expelled slowly over a period of time.
It can take a while. That’s why it is important to regularly check tyres for the correct air pressure. It’s simply done at home with a pressure gauge.
The air loss may not be immediately obvious. It is conceivable, but unlikely due to the general noise that surrounds us, that the owner will be able to hear a slight ‘hissing’ noise. Slow punctures can occur any time for a number of reasons.
As mentioned, the damage may be due to a nail or a small sliver of glass piercing the tyre tread. A sharp strike against an edge or bad pothole could cause an air leak too. It is also not unknown for a tyre valve to work loose. These are simple to tighten and at least it means that the tyre itself is intact.
Can a slow puncture cause a blowout?
Yes, in certain circumstances it can. A fully inflated tyre feels solid to touch. Manufacturers recommend ideal pressures to ensure the rubber tread works at its best.
Slow air leaks weaken the side-wall of the tyre. It collapses down upon itself and this is turn can break the bead seal around the edge of the wheel rim. Thus, not only will the tyre be holed, it may also be damaged beyond reasonable repair meaning more unnecessary expense.
The worse case scenario is that the tyre will suddenly blow or roll off the rim causing the car to veer sharply. At almost any speed worth mentioning this could cause a bad accident and subsequent injury to occupants and other road users. The tyres we buy really are important to road safety aren’t they?
How to spot a slow puncture?
On a stationary vehicle a visual and audible examination is possible if a slow puncture is suspected. If it seems like there is a problem the driver should not use the car. They may be warning signs:
- Tyre pressure monitors:
Increasingly, new cars on the road are fitted with tyre pressure monitors. As the name suggests these monitors keep tabs on the air pressure within the tyre and when a fault develops, notifies the driver on the dashboard screen.
Most systems have the monitor fitted in the tyre behind the valve. That way an accurate check can be made. Any deviation from the correct pressure is notified to the driver for attention.
The only downside is that the monitors themselves are powered by a tiny battery and over time they, like any battery, can run down, potentially given a false, or no, reading. That’s why drivers should pay attention to other physical signs as well.
- Constant topping up:
Every motorist should regularly check tyre pressures. All tyres lose a little air over time naturally. If nothing else, maintaining the correct air pressure will ensure the tyre works at optimum performance and will thus last longer.
It only takes ten minutes at the local filling station but note that some garages don’t calibrate their gauges very often, or at all, so it’s better to do it at home with a combined pressure gauge and pump from a good brand. If for some reason this isn’t possible, ask your local tyre professionals to check it for you. Most will oblige.
- Obviously flat:
Even the inexperienced eye can see when a tyre is flat. Having reached that stage the only recourse is to seek help or deploy any resources carried on the vehicle (see below).
How to identify a slow puncture while driving (Signs)
While it is possible to be driving on a slow puncture unknowingly, after a while the car will give certain hints that something is not right. It would be a foolish driver indeed who ignored these warning signs:
- Handling issues:
The driver may notice that the car is behaving oddly. For example, constant straight line correction may be necessary. The driver might notice that the car is veering in one or other direction, depending upon where the puncture is.
This will be especially noticeable on a front-wheel-drive car where the wheels have to take care of both propulsion and steering. If events like this occur it is best to stop as soon as is practicable and check, if necessary changing to the spare and driving to a professional tyre service.
- Vibrating steering wheel:
This one is obvious. In the same way that a car’s wheel can be knocked out of balance, setting up a vibration through the steering wheel, so it is also true for a puncture. The faster the car is driven, the worse the vibration gets. Any steering wheel vibration should be immediately investigated as matter of urgency.
- A change in ride quality:
The driver or passengers may notice that the ride is not as smooth as it should be. A soft tyre will thump over rough or worn road surfaces. The air pressure in tyres forms part of the suspension of a car for ride comfort.
Over rough surfaces a tyre will deform to absorb low-level impacts as it is designed to do. It’s not an issue, tyres are designed to take the punishment, but a change in ride quality will become more noticeable as the tyre deflates.
Can you drive with a slow puncture?
Yes, but it should only to be to get to a safe stopping place or to a tyre fitting bay. Air leaking slowly from tyre will initially give a bit of a grace period but it won’t last long.
The further the car is driven, the softer the tyre will get to the point where the tyre side-wall will collapse and that will be the end of the tyre. Side-wall damage cannot be repaired.
Will my tyre pressure monitoring symptoms (TPMS) alert me?
The tyre pressure monitoring system (usually shortened to the acronym TPMS) is, as described above, a device fitted behind the valve within the tyre, one in each of the four and the spare, if carried.
It is battery-powered and constantly checks the air pressure inside the tyre. It is set to read the correct pressure and, if a slow leak is incurred, will send a warning message to the driver via the dashboard screen or centre console.
Drivers will normally see the pressures shown individually for each wheel at each corner making it obvious which wheel has the problem. It’s worth noting that, as they are battery powered, in time the battery will be exhausted but it’s not really an issue; the tyre will probably need renewing in good time anyway.
How to repair a slow puncture
Car tyres are not like bicycle tyres; it is not just about doing a roadside patch on an inner tube. The days when a driver could fix a puncture by replacing the inner tube are long gone: Tubeless tyres have ruled the market for decades.
If the slow puncture is small and on the tread itself it is possible to repair a car at home but definitely not advisable unless the owner really knows what to do. Home kits are available to buy but it far better and safer to take the flat tyre to the local professional tyre fitting service for a proper repair.
The process is called vulcanising and it involves first removing the cause and then taking a patch and rubber-welding into place. On a fairly new tyre on a mainstream car this should be sufficient. There is no point in repairing a worn tyre. The technician will advise.
In the case of some specialist tyres on, say, a high-performance car, repair is not advised and the tyre should be replaced. If the tyre is to be repaired it is perfectly acceptable to drive on a legal spare for the duration. These days though, some cars no longer carry spares but have ‘get-you-home’ kits instead. This is to save weight.
The kits will inject a substance into the tyre, inflating it and temporarily filling the leak while the car is taken to to a repair bay. Tyres treated in this way or that have damaged side-walls cannot be repaired. Similarly, with ‘run-flat’ tyres it is likely that the unit will have to be replaced as the technicians may not be able to see any secondary damage.
Why it’s important to repair a tyre’s puncture
If the air leak is slow and doesn’t seem to be getting any worse, the temptation is to keep going. The driver may, for example, be able to see the nail head in the rubber and consider that it is preventing any bad leaking.
It’s just easier to top the air up every morning right? Wrong. If there is such a place, the best place for a puncture to be is somewhere on the central three-quarters of the tyre tread. Anywhere near the side-wall and repair is not advised.
That said, in the same way that a light shower can quickly turn into a torrent of rain, so that nail will be slowly working away, enlarging the damaged area and the resulting blowout could cost a lot more than an early repair.
How long will it take on average for a slow puncture to go down?
There’s no definite answer. A punctured tyre can turn into a flat tyre very quickly. Alternatively a small invasive object might only allow a little air to leak so there is not a straight answer. The solution of course is just to fix it as soon as possible.
Summary – How to tell if you have a slow puncture
The condition of your car or indeed motorcycle tyres are a vital part of being safe on the road. Families and pillion passengers are precious cargo. Don’t take any chances with punctures, get them repaired or replaced immediately.
