Bootstrap's collapse() sets dimension to 'auto'.

Setting the dimension to auto trashes whatever was previously set.

HTML

<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<script src="http://netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
<div class="container">
    <div class="row">
        <div id="collapse" class="col-xs-1 collapse width in">
            <div>
                A fair amount of text.
            </div>
        </div>
        <div class="col-xs-11">B</div>
    </div>
</div>
<button id="toggle">Toggle</button>

JavaScript

$(function () {
    $("#toggle").click(function () {
        $("#collapse > div").collapse('toggle');
        return false;
    });
});