The only "steerable" wheel on a Chinook is the RH rear and this puts it under quite a lot of strain when turning - and to taxy with due consideration, I remember being well aware of this during ground ops. I also seem to remember that we were told that the rear u/c legs were a weak point in an otherwise incredibly tough aircraft. I was told in my conversion (to a BV234 which is identical in most respects) that this wheel had a history of falling off occasionally and I think (I cant find my old checklist right now) that we had a procedure in there to deal with it - like Don't land until there's a cushion of tyres or similar.
Hardly a big dealthough, is it?