Trials 2 is rather sensitive to other programs running simultaneously in background and to many (often invisible) background processes. Something simple as an email/messenger message popup, windows search indexer or background virus scanning can make the game lag very badly.
Also the game streams textures on fly and runtime virus scanners will cause streaming hiccups (scanner blocks the game execution for the file scanning period). If you have a runtime virus scanner active, I suggest adding Trials 2 directory to your virus scanner exception list. And you get also a nice bonus: The game loading time will be reduced considerably.
We have planned to adjust Trials 2 SE process priority up a bit to improve the situation with background processes.
If you are running on windowed mode, I suggest trying fullscreen mode instead, as the fullscreen process gets a bit more CPU time, and has exclusive access to the graphics card.

