What about concentrating on Cavendish? As you're finding out, it is very hard to discuss 'greats' in cycling without drugs references. There's an article in another part of the forum about how this year's tour was slower up the Alps - but was better (drugs free) for it.
Cavendish is in mid-career, but destined to be one of the best of all. Like Cadel
Evans, he's generally accepted to be drugs-free. There is plenty on the internet about how he got to the top, and how he stays there.
We may be moving into an era when we can trust cycling results. If so, Cavendish will have spanned the end of one period and set the highest standards for next. Well worth celebrating. He'll be getting his place in the house of lords about the time you leave college.
Good luck with the essay, whatever you choose.