If you're wearing the wrong size around the body (for example, you're wearing a size 14 instead of a 16), the bra is overstretched. This forces the underwire out of shape with repeated stress and tension on the metal. This can cause the metal to fracture and break free or force the wires through the casing.

Why do my bras keep snapping?

Your bra band is too tight. – Underwires are designed to splay when the bra is worn. ... If your bra band is too tight, you are pulling the underwires apart farther than they are designed to be pulled. This stress will eventually cause the wires to break.

Why do my bra wires keep coming out?

When the underwires pop out of the underwired bra it is often a sign that the bra band size is not correct. If the band size is too tight then the underwires are placed under pressure and may poke out the front overtime. ... Also washing your bra in hot water can shrink the channelling and force the underwire to pop out.