I know this is like two years late…
// In your html/template - Note that the object here can be defined as a public item on your component script also
<ion-select [selectOptions]="{'cssClass': 'wider-popover'}"...
<ion-option...
-------------------------------------
// In appropriate css
.wider-popover .popover-content {
width: 100%; //or w/e width
}
The select will propogate that class to all necessary children, thus allowing .popover-content’s width to be set with a little more specificity.
Cheers