Never ever ignore a bulge!
If you have a bulge in the sidewall of your tyre – whether your vehicle is a car, van or truck – it means that the fundamental structure that holds the tyre together has been damaged and you must put your spare on and replace it immediately.
The diagram below shows the structure of a tyre.
If you look at the body plies that run from bead to bead across the tyre you will see that they make up the main shape and structure of the tyre. A bulge occurs when one or more of these threads break. Without these threads to hold the structure of the tyre together the air will try to escape through this breach. This creates a bulge and a very weak point. Hit a bump, a kerb or a pot hole and the air will take the opportunity to escape in a hurry. The violence of the explosion varies depending on a number of factors like the weight of the vehicle, the air pressure in the tyre and the size of the bulge. Either way, the tyre will blow out and may cause you to lose control of the car.
This is why it is so important to check your tyres regularly and never ignore a bulge.
Bulges mostly occur after hitting a kerb or having an accident but occasional flaws in the tyre’s manufacture can lead to ply threads snapping after going over pot holes or speed bumps.