I was suggesting to my navigator (I drive a rally car) that she buy a new helmet, because her old one was rather old and the lining was starting to fall apart a bit. She welcomed the idea, but then found out that Clark Rubber apparently fairly often replace the lining in older helmets. I think they use some sort of impact resistant foam or something, I would guess it is the same stuff that is already in the helmet. Has anyone else done this before? I would have thought that the lining is a very integral part of the helmet and probably the most important part of the helmet as far as preventing head injuries goes, and I would have thought it would be what really makes a good helmet a good helmet?