Shortly before it happened my chain was skipping a bit (by pulling the catoad reared then jumping back) and I stopped to have a look at it. Got talking to a chap who also fitted an upper in the lower position and he said his dereillieur exploded. About a minute later mine exploded. He’d said it was something to do with slightly different profiles or widths or something like that.
Edit: Oggles that sounds about right. Did make quite a mess.
when it wears out or you break it, buy x9 instead.
Sram X0 2011 10sp rear mech
RRP: £209 (can be had for £145 online)
Sram X9 2011 10sp rear mech
RRP: £99 (can be had for £59 online)
so seriously is it actually worth £100 extra to save 10g?
and even *if* the X0 shifts slightly better and lasts slightly longer – which has not been my experience after having had both X0 and X9 mechs – then it still works out better to just buy X9 slightly more often (or keep a spare at home)