(There's no setup subforum and a search brought up no appropriate threads, so here goes.)
When DiRT Rally was released I made a setup sharing thread, which you can find here: http://forums.codemasters.com/discussion/40847/dirt-rally-setup-sharing-thread/p1
As DiRT 4 doesn't have any in-game setup sharing options I figured another thread would be useful.
In most racing games, having the right setup can be crucial to getting the fastest stage times. This is a thread where we can share our setups and give tips to others.
If you're a Steam user you could download setups from the Steam Workshop in DiRT Rally, but I haven't found anythign similar for DiRT 4.
If you're on Xbox or PlayStation 4 however you'll have to rely on people posting screenshots, as those versions definitely don't have a way of distributing setups in-game.
Some extra link(s):