PUT HTTPClient doesn't seem to be working

I have tested PUT using the Poster plugin for firefox and it works as expected but when I run a function containing the following nothing happens not even a stauscode so am I doing something wrong?

var url = 'http://www.example.com/api/update/' + id;
    var xhr = Titanium.Network.createHTTPClient({timeout: timeout});
    xhr.onload = function() {
        if(xhr.status == 200) {
            var response = xhr.responseText;
            var data = JSON.parse(response);
            Ti.API.info(data);
            onSuccess(data, xhr.status);
        }
    }
    xhr.open("PUT", url);
    xhr.send();