Isn't the game local host only? Didn't think it has dedicated servers.
Dedicated server options are WIP, sometimes the standalone server tool (can all see it in Steam > Library > Tools?) and pCARS loses sync because of updates, in which case all would need to fall back to the current default of peer-to-peer hosting.
To create a server on a publicly available dedicated server, use the following Steam launch command in Library > pCARS> properties...
-autods
Other launch commands to try include...
-skipcrowds (lose crowd for a small fps boost)
-pthreads "x" (where "x" is 3 or 4, spreads physics over more threads than the default 2)
-x86 (force pCARS to run in 32-bit)
-x64 (run in 64-bit, default if you have a 64-bit cpu)
-dx9 (run in DirectX9, but this path received very little optimisation "love" for ~2 years)
-dx11MT (activate multi-threading graphics, default is single thread)
Simply put a space inbetween each command eg. I currently use...
-pthreads 3 -skipcrowds -autods