On this page
- What does it mean if a tyre slowly loses air?
- Where can the air be escaping from?
- Can cold weather make tyres go down?
- What should you do if a tyre is losing pressure?
- Can you drive on a tyre that's losing air?
- Can a pressure leak be repaired?
- How does SOS Tyre deal with a tyre that's losing air?
- Frequently asked questions
What does it mean if a tyre slowly loses air?
If a tyre slowly deflates, there's a small pressure leak letting air out over days or weeks. You usually notice because the tyre pressure warning light comes on, because you keep having to reinflate the same tyre, or because it looks lower than the others.
It's not an emergency like a puncture, but it does need sorting: an underinflated tyre uses more fuel, wears unevenly, brakes less well and heats up, to the point of risking damage to its structure.
Where can the air be escaping from?
The air almost always escapes from one of these points. Working out which one is the first step towards choosing the right solution.
| Cause | Typical signs | Usual solution |
|---|---|---|
| Small hole in the tread | A visible nail or screw, constant leak | Repair, if the hole is in the repairable area |
| Valve | Missing cap, cracked or bent valve, hissing near the valve | Replacement of the valve or its core |
| Bead or rim edge | Leak after hitting the kerb, or on a corroded rim edge | Removal, cleaning and restoring the seal |
| Porous or cracked rim | Slow leak with no obvious holes, often on older alloy wheels | Rim check, sometimes needs replacing |
| Drop in temperature | All tyres lower on cold mornings | Bring the pressure back to the correct values |
Can cold weather make tyres go down?
Yes, when the temperature drops, tyre pressure falls even without any leak, because the air contracts. That's why in autumn and on winter mornings the tyre pressure warning light can come on for all four tyres at once.
The difference from a real leak is simple: with the cold, all the tyres drop by a similar amount and, once the pressure is restored, they stay stable. If it's always the same tyre that goes down, there's a leak to find. Measure the pressure when the tyres are cold, i.e. before driving very far, and compare it with the values shown on the label on the door pillar, inside the fuel filler flap or in the owner's manual.
What should you do if a tyre is losing pressure?
- Measure the pressure of all the tyres when cold and compare it with the manufacturer's values.
- Bring the tyre back to the correct pressure with a compressor or at a petrol station.
- Check the tread for nails or screws, without removing them.
- Look at the valve: make sure the cap is there and the rubber isn't cracked.
- Check the pressure again after a few hours or the next day to see how fast the leak is.
- If the tyre goes down again, have it checked without delay.
If the tyre empties within a few minutes or is already nearly flat, follow the advice for a flat tyre instead.
Can you drive on a tyre that's losing air?
You can drive on a slowly leaking tyre only if the pressure has been restored to the correct value and the leak really is slow. In that case, keep an eye on the warning light, avoid high speeds and heavy loads, and have the problem fixed soon.
Don't drive if the tyre is visibly squashed, if the warning light comes back on after a few kilometres or if you feel the car pulling to one side. Driving for a long time underinflated damages the internal structure and can make a tyre that could have been saved unrepairable.
Can a pressure leak be repaired?
In most cases a slow leak can be fixed without replacing the tyre: a small hole in the tread can be repaired, a valve can be replaced, and a leak at the bead can be cured by cleaning the rim edge and refitting the tyre. It's a different story with a cracked rim or a tyre with sidewall damage, which need replacing.
For the general criteria, read when a tyre can be repaired.
How does SOS Tyre deal with a tyre that's losing air?
SOS Tyre comes quickly to wherever your vehicle is, in Milan or its province, to find the leak and fix it, including outside your home or at the office as a mobile tyre fitter. Call +39 377 326 0999 or fill in the assistance request.
It helps us to know:
- where the vehicle is and whether it's on the street, in a courtyard or in a garage;
- make, model and type of wheels;
- the tyre size;
- how often you have to reinflate the tyre, plus a photo of the wheel.
The technician assesses an on-the-spot repair when the cause allows.
Frequently asked questions
How often is it normal to reinflate tyres?
All tyres lose a little pressure over time, which is why it's recommended to check it at least once a month. If, however, you have to reinflate the same tyre every few days or every week, that's not normal loss: there's a hole, a faulty valve or a sealing problem at the rim.
How do I find where the tyre is losing air?
A simple method is to spray soapy water over the tread, around the valve and along the edge of the rim: bubbles form where air is escaping. If you find nothing, the leak may be internal or at the bead, and the tyre needs to be removed to locate it.
What is a porous rim?
A rim is described as porous when its alloy, because of casting defects, corrosion or ageing, lets small amounts of air through. The result is a slow leak with no holes in the tyre. A tyre fitter identifies it by removing the tyre and checking the rim's seal.
Does the valve cap really matter?
Yes. The cap protects the valve's internal mechanism from dust, water and dirt that can compromise the seal and cause slow leaks. If it's missing, replace it: it's a small precaution that prevents pressure problems.
Does inflating tyres more stop them going down?
No. A pressure higher than the manufacturer's recommendation won't stop the leak and makes grip, comfort and tread wear worse. The solution is to bring the tyre back to the correct pressure and have the cause of the leak repaired.