Some good news. I recently found ways to make the mud better (more realistic in my view) and I decided to share them here if anyone is interested and doesn't already know about this. And I'm talking about both visual and physical properties.
To remove those oversized ugly mud chunks from tires:
In the game's installation folder, remove env_mud_particle from MeshCache.zip.
To make mud stickier and more realistic:
In the game's installation folder, extract file media.xml from Media.zip and change the value SubstanceFriction in the mud section from 2.2 to 1.8, save the file and copy back to the zip.
This is the value I found best so far. Your ideal value may be different, but if you want more realism, give it a try. FYI, I was testing with the C-375 in the Proving Ground's swamp with diff lock on but without 4wd, to see how effectively I get stuck in the deep mud and need 4wd to get out. With the original value, I feel it's too easy to climb out. If the current values seem fine to you, then just carry on with your mud running.
I want to say though that this is not the ideal fix to the mud. I feel the mud is good like this, but to make it perfect, where the undercarriage of a truck actually gets stuck in mud where even 4wd + diff lock won't get you out (which happens in real life as the tires start spinning in the air) the devs would need to change the code so that if the truck gets to or below the maximum mud depth, then it won't have any traction and won't move at all. Only winching the truck out would help it in that case.
For even more realism and to summarize my research since I started this thread, try these settings:
In media.xml, use these:
<Mud> <Substance FullPushDepth="0.9" LinResistance="1.8" PushResistance="36.0" SubstanceFriction="0.3" /> </Mud>
In _templates\trucks.xml, use these. This mainly increases pavement traction to reduce the excessive wheel spin that MR has on pavement, while not allowing vehicles to climb ridiculous slopes.
<WheelFriction> <Offroad BodyFriction="1.3" SubstanceFriction="1.2" /> <Default BodyFriction="1.5" SubstanceFriction="0.8" /> <Highway BodyFriction="1.6" SubstanceFriction="0.5" /> </WheelFriction>
Keep in mind mods and a few of the DLC vehicles have their own wheel friction settings that will override these. I recommend to remove those custom values and go with the template values instead. See one of the stock wheel xmls (in classes\wheels in media.zip) for an example of what it should look like.