Trummer began his motorsport career in karting back in 2003, finishing second in the Swiss Junior Championship.

Trummer joined the BMS Böhlen Motorsport team in 2007, to compete in the Formule Renault 2.0 Suisse championship.

[2] He finished the season in 25th place with four points, despite missing the round in Hungary due to driving into the rear of another car in Hockenheim.

During 2010 in GP3 with Jenzer Motorsport he was always outperformed by fellow Swiss driver Nico Müller which lead Simon to seak another team for 2011.

After competing in the non-championship season finale at Yas Marina in 2011, Trummer continued his collaboration with Arden International into 2012 by switching to the GP2 Series full-time.