Facing this problem, I made the following addition to my css stylesheet:
#mainContent .container {
padding-left:16px;
padding-right:16px;
}
#mainContent .row {
margin-left: -8px;
margin-right: -8px;
}
#mainContent .col-xs-1, #mainContent .col-sm-1, #mainContent .col-md-1, #mainContent .col-lg-1, #mainContent .col-xs-2, #mainContent .col-sm-2, #mainContent .col-md-2, #mainContent .col-lg-2, #mainContent .col-xs-3, #mainContent .col-sm-3, #mainContent .col-md-3, #mainContent .col-lg-3, #mainContent .col-xs-4, #mainContent .col-sm-4, #mainContent .col-md-4, #mainContent .col-lg-4, #mainContent .col-xs-5, #mainContent .col-sm-5, #mainContent .col-md-5, #mainContent .col-lg-5, #mainContent .col-xs-6, #mainContent .col-sm-6, #mainContent .col-md-6, #mainContent .col-lg-6, #mainContent .col-xs-7, #mainContent .col-sm-7, #mainContent .col-md-7, #mainContent .col-lg-7, #mainContent .col-xs-8, #mainContent .col-sm-8, #mainContent .col-md-8, #mainContent .col-lg-8, #mainContent .col-xs-9, #mainContent .col-sm-9, #mainContent .col-md-9, #mainContent .col-lg-9, #mainContent .col-xs-10, #mainContent .col-sm-10, #mainContent .col-md-10, #mainContent .col-lg-10, #mainContent .col-xs-11, #mainContent .col-sm-11, #mainContent .col-md-11, #mainContent .col-lg-11, #mainContent .col-xs-12, #mainContent .col-sm-12, #mainContent .col-md-12, #mainContent .col-lg-12
{
padding-left: 8px;
padding-right: 8px;
}
This overrides the default bootstrap styling and makes the left and right sides and the gutter equal width.