McManus began his road racing career in 2015, competing in two championships where he took first place in the Ulster 125cc and second in the Irish 125cc. From there, he embarked on the British Motostar Moto3 series for the next three seasons, finishing 13th, fifth and eighth in the championship. During his 2018 season, he also entered the GP2 category taking a victory and a podium in the process.

In 2019, McManus stepped up into the British Supersport class however, his season did not go to plan after being involved in a season-ending accident onboard the Yamaha at Brands Hatch in the fourth round, resulting in him being unable to compete.

He moved into the National Superstock 600 class in 2020 after regaining his fitness, and remained in this championship during the 2021 season. It was this season where he started picking up the silverware with five podium finishes, resulting in a fifth place championship standing at the end of the season. Not wanting to let that supersport desire disappear, he also competed in two rounds of the World Supersport championship, an experience he repeated in 2022 and 2023.

That 2022 season bought him back into the British Supersport championship where he continued to be a regular contender in the British Supersport series for several seasons finishing eighth in the 2022 championship, followed by ninth in 2023, then his best result yet of fourth in the championship for 2024.

Collecting a number of podium finishes and placing sixth overall in 2025 proved to be enough consistency and development for the Hawk Racing team to offer McManus a British Superbike ride for the 2026 season.