Byrne stormed ahead of his rivals on his Rapid Solicitors Kawasaki, topping the sheets in a time of 1:38.651.
He completed an initial run of 14 laps to test his troublesome shoulder before completing the session with an inspired tilt.
Alex Lowes, on his WFR Honda, put his previous experience of testing the World Championship bike to use as he led until the closing minutes of the session, and ended second fastest.
Josh Brookes moved back up the order on his final stint on the circuit to go third fastest on the Tyco Suzuki, ahead of Luca Scassa on the leading Padgetts Honda, who has extensive circuit knowledge from his time in the World Supersport Championship.
Overall standings leader ahead of this weekend, Tommy Hill, was fifth fastest ahead of Swan Yamaha team-mate Noriyuki Haga after having led the early stages of the session.
Free practice one results
Shane Byrne (Rapid Solicitors Kawasaki) 1:38.651
Alex Lowes (WFR Honda) +0.482s
Josh Brookes (Tyco Suzuki) +0.549s
Luca Scassa (Padgetts Honda) +0.627s
Tommy Hill (Swan Yamaha) +0.904s
Noriyuki Haga (Swan Yamaha) +0.934s
Tommy Bridewell (Supersonic BMW) +1.257s
Jakub Smrz (Splitlath Redmond Racing) +1.298s
Ian Lowry (Padgetts Honda) +1.354s
Jon Kirkham (Samsung Honda) +1.378s
- Josh Brookes