You must ride fast, Quinny. I just had a thought, maybe it's because the smell is a bit like whoopee cushions, so it could be a comfort thing. As in reminding me of childhood, not that I find whoopee cushions inherently calming.
I do like the smell of tyres, but not just any tyre, it has to be an M & S tyre freshly unpackaged from its perspex presentation case, the protective bubble wrap discarded and then the inner plastic protective film removed.
Although I'd like to add to my earlier statement that I don't like the smell of Continental tyres. They make me feel queasy. Anything else and we're ok (not that I habitually sniff tyres of course...)