Came across this, thought it may be useful to you guys with heavy gear:-
http://www.ebay.co.uk/itm/5-Tyre-Se...783721?hash=item4b0f646069:g:zCsAAOSwjDZYbj75
http://www.ebay.co.uk/itm/5-Tyre-Se...783721?hash=item4b0f646069:g:zCsAAOSwjDZYbj75