Tyre bulge: why it happens and why it cannot be repaired

A tyre bulge is a swelling on the sidewall, like a blister or a bubble, and it means the tyre’s internal structure has been broken. The sidewall of a radial tyre is held in shape by layers of cords, the carcass ply. When a hard knock from a pothole or kerb snaps some of those cords, the air pressure pushes the rubber outwards at the weak spot. A bulged tyre can lose all its air suddenly, so it should be replaced, not repaired and not driven on at speed. Indian rules agree: a tyre showing local swelling is not considered to be in sound condition. And because a bulge is almost always impact damage, most standard warranties will not pay for it.

What a tyre bulge means

Michelin describes a sidewall bubble as a sign that the carcass ply behind the rubber has been punctured, and calls it one of the most alarming signals a tyre can give. Once the cords are broken, only a thin layer of rubber is holding back the air at that spot. If it gives way at highway speed, the sudden loss of pressure can cost you control of the car.

A bulge can form on the inner sidewall, facing the suspension, as well as on the outer one, so you may not see it on a walk around the car. Michelin notes that a bulging tyre usually causes unusual vibration, which is often the first clue.

What causes a tyre bulge

Potholes and kerbs. Michelin names both: driving onto a kerb, straight on or at an angle, or dropping a wheel into a pothole can break the cords inside the sidewall and leave a bulge.

Not speed breakers. Michelin says speed bumps, which are sloped on both sides, may be hard on suspension but do not damage the tyre in this way. The danger is a sharp edge, not a rounded hump.

If you hit something hard, stop when it is safe and look at both sidewalls of the tyre, and have it checked if the car vibrates afterwards.

Bulge or normal ripple?

Not every unevenness in a sidewall is damage. Michelin points out that slight deformations are normal in radial tyres, often where the internal plies overlap. These are slight and usually read as a shallow dip or ripple. A bulge looks different: a bubble standing out from the sidewall. If you are unsure which you are looking at, have a tyre shop check it before your next long drive.

Is it safe to drive with a bulging tyre?

No. Fit the spare and drive on that. If there is no spare, drive slowly and directly to the nearest tyre shop, avoiding highways.

The law treats it the same way. Rule 94 of the Central Motor Vehicles Rules requires tyres to be kept in good and sound condition, and says a tyre is not sound if it “shows signs of incipient failure by local deformation or swelling”. A bulge is exactly that.

Can a tyre bulge be repaired?

No. Michelin explains the difference: a puncture in the tread can be filled and the tyre driven again with the same performance, but a sidewall that has been punctured or damaged cannot regain the flexing qualities it needs, so the tyre must be replaced. The CMVR rule specifically refuses to count a tyre patched with an outside gaiter or patch as sound, except as a temporary fix to reach the nearest repair shop. Any shop offering to fix a bulge is offering something unsafe. Our puncture repair guide covers the damage that can be mended.

Will the tyre warranty cover a bulge?

Usually not, because a bulge is almost always impact damage, and standard warranties cover only manufacturing defects. MRF’s policy says its warranty ceases if the tyre suffers road hazard damage such as an impact break. Apollo’s says the warranty is no promise against impact breaks caused by road hazards and lists impact damage among its exclusions.

There are two partial exceptions:

• Extra cover schemes. CEAT’s additional warranty on non-manufacturing damage lists concussion (impact) damage among the covered causes, for a limited period that depends on the tyre type. JK Tyre’s JK Assure covers non-manufacturing damage that makes a passenger car tyre unusable for two years from manufacture or up to 50% tread wear, on a pro-rata basis, if the tyre was registered. If you have one of these, claim it.
• A genuine defect. If you are sure the tyre took no knock, the maker’s inspection decides whether the failure was a defect. Take the tyre to an authorised dealer with the invoice.

Our tyre warranty guide covers claims in detail.

How to lower the risk of a bulge

You cannot avoid every pothole, but you can make a bulge less likely and catch one early:

• Keep pressures right. Michelin’s first piece of advice on sidewall damage is to keep tyres at the pressure on the car’s placard. Check them monthly, with the tyres cold.
• Slow down for broken roads. Michelin’s advice is simply to avoid potholes when you see them. Where you cannot, a lower speed means a smaller impact.
• Look after a knock. If you do hit a kerb or pothole hard, Michelin recommends having the tyres checked for damage, inside and out.
• Inspect regularly. A quick look at every sidewall, and the spare, every few weeks catches cuts, cracks and bulges before a long trip.

What to do after finding a bulge

1. Stop driving on the tyre at speed. Fit the spare if you have one.
2. Check the other three tyres, including the inner sidewalls, especially if the bulge followed a single big impact.
3. Replace the damaged tyre with one of the same size, load index and speed rating. Our tyre size pages help you find it.
4. If the other tyre on the same axle is well worn, ask the dealer whether replacing both makes sense.
5. Ask the shop to look at the wheel rim as well while the tyre is off.

If your car runs on run flat tyres, have any hard knock checked even without a visible bulge, and for fine cracks rather than swelling, see our guide to sidewall cracks.