Tour de France, Giro d'Italia and Vuelta a España winner Nibali will be appearing at the show on Sunday, September 24.
The 32-year-old Bahrain-Merida pro had originally been touted as taking part in the Road World Championships on that date, but it was discovered that he had fractured his ribs in a crash during on the penultimate stage of this year's Vuelta.
Nibali finished second overall to Chris Froome (Team Sky), despite the injury.
Nibali will appear on stage for a question and answer session, and then sign autographs and meets fans on the FSA stand.
Dowsett will be at the show on Friday, September 22, and will be at the Canyon bikes stand for a signing session from 1pm with a a Q&A session at 2pm on stage.
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