What causes a bubble in a tire?

Car tires have their own “diseases” – blisters. These deformities are very similar in appearance but have different causes. In this article, we’ll take a closer look at the causes and appearance of these similar keel and bubble deformities, and tell you how to avoid them.

It is not uncommon for even a brand-new tire to have a blister. Naturally, a responsible car owner’s first action is to return the tire to the store where it was purchased and return it under the pretext of a manufacturing defect. But the store representatives decide to look at the tire and the customer starts suspecting something wrong because there is a defect on the front side! To understand the reason it is necessary to disassemble the tire and examine it from the inside. It is the underside that will help answer many questions: whether it is a defect, a mistake during tire fitting, or improper use.

First, let’s take a visual look at examples of blisters that are manufacturing defects.

A manufacturing defect is known as a thread divergence in the cords of the carcass layer. If you look closely, you can see that the distance between the threads is greater than their thickness. This manufacturing defect is not allowed in the production of radial single-ply tires. The hallmark of such a defect is the mirror-like nature of the defect – the bubbles appear opposite each other. There can be a bubble where there are no cords at all.

In the above examples, the blister is the result of the deformation of the tire sidewall due to stretching of the rubber layer between the cords. This defect occurs when the tire is first mounted on a rim and then inflated. Therefore, immediately after mounting with a new tire, the tire should be inspected for the occurrence of a hernia.

Shocks during operation

Next, let’s look at blisters caused by tire sidewalls collapsing. The distinguishing features of such blisters are dark spots (both on the front side and the underside of the tire). These marks are the traces of a wheel hitting an obstacle. The area of the spot depends directly on the force of the impact, the size of the obstacle, and the speed at which the car was moving. In this case, the cord threads are torn, the rubber compound of the sidewall loses its reinforcing layer, and the sidewall is warped.

The photo shows in detail the various ways in which the cords are broken when hitting various obstacles: spots and dents in the sealing layer, tears in the rubber sealing layer, and through holes in the sidewall can be seen. In the case of the latter (puncture), when the air has somewhere to escape, no bubble is formed. It is also important to understand that such bubbles are an unrepairable case. If the situation is urgent and it is impossible to replace the tire with a bubble for a new one, craftsmen resort to the variant with a riding tube, which somewhat smoothes the arose hernia. Naturally, this is a variant of the spare wheel, not a full-fledged wheel.

Hitting obstacles while driving leaves marks not only on the tire itself but also damages the rim flanges. Corresponding chips and scratches can be equated to evidence of an impact that occurred.

Side ties

In addition to bubbles, there is such a thing as side ties. They appear only on an inflated tire and indicate the peculiarities of the processing of the cord joints during production. A side tie is difficult to diagnose visually but can be found quite quickly by touch. Simply put, this is where the edges of the tire carcass overlap each other.

Lateral overlap is not a manufacturing defect until it is recognized that it negatively affects the force heterogeneity and lateral runout of the wheel.

At the time of purchasing a new set of tires, any customer can inspect the tire themselves to see if there is any discrepancy in the backside cords, air bubble pockets, and side ties. However, there are cases where a “hernia” appears for no apparent reason, in the absence of aggressive driving and hitting obstacles. It grows gradually and does not show up in statics.

Poor quality tire fitting

This is a defect in the tire fitting. Unqualified mounting, of course, can also cause a tire hernia. The photo perfectly shows the deformation of the bead ring, which could only be allowed to occur when mounted on a wheel rim.

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