How long can I drive on a slow puncture?
Only far enough to reach somewhere safe. Keep it under about five miles, at low speed, ideally below 30mph, and head straight for a safe place or a fitter rather than carrying on with your day.
A slow puncture is not a stable condition that you manage. It is a leak that is getting worse. As pressure drops, the sidewall flexes further than it was designed to on every single revolution, and that flexing generates heat. Heat is what destroys a tyre from the inside. By the time it looks obviously flat, the casing may already be finished, and a puncture that would have been a cheap repair on Monday is a new tyre by Thursday.
The other reason to keep it short is that underinflated tyres stop badly. Braking distances lengthen, the car wanders under braking, and the risk of a sudden blowout at speed goes up sharply. On the A9 or the Kingsway, that is not a risk worth taking to save a phone call.
What are the signs of a slow puncture?
Slow punctures rarely announce themselves. These are the things drivers actually notice first:
- A tyre pressure warning light that keeps coming back. You top it up, the light goes out, and a few days later it returns. That is the classic pattern.
- One tyre needing air far more often than the other three. If you are putting air in the same corner every fortnight, that corner has a leak.
- The car pulling gently to one side. Usually towards the soft tyre, most noticeable when you briefly relax your grip on a straight road.
- Heavier or vaguer steering, especially at parking speeds.
- A tyre that just looks squatter than its opposite number. Park on level ground and look at both front tyres from a few metres back.
- A visible nail or screw head in the tread, or a faint hiss when you get close.
- Uneven wear across the tread, with the two outer edges wearing faster than the middle. That is the wear pattern of a chronically underinflated tyre.
Any one of those is worth two minutes with a pressure gauge. Not the garage forecourt gauge you use once a year: a cheap gauge in the glovebox is one of the better ten-pound purchases a driver can make.
What causes them
Four culprits cover nearly everything we see:
A nail or screw in the tread. The object seals its own hole well enough to leak slowly rather than deflate at once. This is the good outcome, because tread-area damage is usually the repairable kind.
The valve. Rubber valves perish with age and metal TPMS valves corrode. A tyre losing air with absolutely nothing visible in it is very often a valve, which is why a new valve should be part of every tyre fitting rather than an upsell.
The rim. Corrosion on an alloy, or a kerb strike that has distorted the bead seat, lets air past where the tyre meets the wheel. Common on older alloys and on cars that have spent winters on salted roads, which around here is all of them.
A pothole. Impact damage can crack the internal structure without leaving much of a mark outside. If a slow leak starts the week after you hit something hard, mention it, because the tyre needs looking at properly rather than just plugging.
Can it be repaired, and what should it cost?
A repair is by far the cheapest outcome in tyres. You are paying for labour and a proper internal plug-and-patch, not for new rubber, so it lands at a small fraction of the cost of a replacement.
Whether it is allowed is a safety question, not a price question. UK repairs follow the principles of British Standard BS AU 159, which permit a repair only when:
- the damage is in the central tread area, not the shoulder and not the sidewall;
- the hole is small, the sort of thing a nail or screw makes;
- the tyre has not been driven on while flat, so the casing is intact;
- there is no sidewall damage, bulging or perishing;
- there is no previous poor repair in the same area.
Miss any of those and the tyre has to be replaced. That is not a fitter looking for a bigger sale; it is the difference between a tyre you can trust at 70mph and one that fails without warning. We assess it at the vehicle and tell you which one you have got before we start. Our guide on whether a mobile fitter can repair a puncture goes through it in more detail.
What not to do
Do not keep topping it up. This is the single most common way a repairable puncture turns into a new tyre. Every top-up buys a few more days of the object working deeper and the hole widening, and none of that damage is visible until the tyre is off the rim.
Do not ignore the warning light. A TPMS light that comes back is the car telling you something specific and correct.
Do not rely on sealant as a fix. A sealant canister is a genuinely useful thing to have at 11pm on a rural road, and it will usually get you moving. It is a get-home measure. It coats the inside of the tyre and has to be cleaned out before a proper repair, so always tell the fitter you have used it.
Do not drive to a garage across town on a badly deflated tyre just because that is where the garage is. That is exactly the trip that wrecks the casing. Call somebody who comes to you instead.
Get it looked at where the car is
We come to your home, your workplace or the roadside across Dundee, Perth, Angus, Perthshire and Fife, 24 hours a day. We assess the tyre on site, repair it if it is safely repairable, and if it is not, we source and fit the right replacement on the same visit.
Send us your registration for a price or call Matt on 07449 206 581 and tell him what the tyre is doing. If it is a slow leak and you are somewhere safe, you have time to talk it through properly before anything gets booked.