Somebody just asked me a question I'd asked myself not too long ago. How do you get SpintiresMod to work with ReShade? Which I couldn't find sufficient info to answer properly via google. So I had to figure it out, pretty much, on my own. Since my pride generally prevents me giving up and asking on a forum(or anywhere else for that matter).
Anyhow. This is how I do it.
Install SpintiresMod. Or do nothing if already installed.
Download the installer for ReShade. Click on the ReShade_Setup.exe. Press 'Ctrl" while clicking Select game to get the ReShade32.dll and ReShade64.dll.
Install Reshade as Direct3D 9. Then open the game and do the tutorial setup bit. So when you're done you'll have the reshade-shaders folder and a premade effects/textures.ini configuration setting file in you MR directory. Then close the game.
Open your MR directory. Delete the three d3d9 files(text doc., config settings, and .dll). Then copy and paste the ReShade32.dll to your MR directory.
Go to C:\Program Files (x86)\SpintiresMod\Install and copy the d3d9.dll found there(or wherever SpintiresMod is installed). Then paste it in your MR directory.
Open STM and go to Game settings > Options and make sure the box next to Override original "d3d9.dll" is checked. Then click browse and direct it to C:\Program Files (x86)\Steam\steamapps\common\SpinTires MudRunner\ReShade32.dll(or wherever MR is installed). Click Apply and OK.
Open MR again. Open the ReShade configuration menu(Shift + F2). Go to Settings and add \reshade-shaders\Shaders to the end of the Effect Search Paths. Then add \reshade-shaders\Textures to the end of the Texture Search Paths. You can also set whatever else how you want it now too(like the Effects Toggle Key). These settings will then be stored in the ReShade config settings file in your MR directory(which will be created in step 8).
Then go to the Home menu again and click continue to start the tutorial again. EXCEPT this time selecting your premade effects/textures.ini from the start(click the down pointer to the left of +, it will show up below the bar, click on it to select it, it will jump up into the bar). Then click your way through the rest of the tutorial and go to Settings if you want to select performance mode. Then go to the Home menu one more time and click Reload. Aaaaaaaaaaaaaaaaaaaaaaannnnnnnnnnnnnnnndddd....................wait for it.................................YOUR DONE!
I know. It's convoluted AF. But it works. If you know a better/faster way please do tell.
EDIT: I figured out that you don't need to close and reopen MR between steps 7 & 8. Just use the Reload feature when everything is setup how you want it.
UPDATE(3/22/18): Our friend @blasc has suggested a, perhaps, better way. By simply renaming the .dll installed by ReShade to dxgi.dll. "Better" in the sense that you might be able to get better framerates by using this method. It shouldn't matter which .dll was installed by ReShade. It can be d3d9.dll, the manually installed ReShade32.dll, or even opengl32.dll. ALL 3 RESHADE INSTALLED .DLL FILES ARE IDENTICAL EXCEPT FOR THEIR NAMES(I'VE CONFIRMED THIS BY COMPARING ALL OF THEM WITH A HEX EDITOR). So I'm not sure how or why changing the name of the .dll makes any difference(but let's assume it does). All I do know is you can change the name of any of the ReShade installed .dll files to dxgi.dll and end up with the exact same file. I don't really want to rewrite my method above to include this. And, so far as I can tell, I don't really have to. All one needs to do is rename whichever ReShade installed .dll(d3d9.dll or ReShade32.dll) to dxgi.dll, and rename the config settings file(d3d9 or ReShade) to dxgi. The d3d9 or ReShade32 text document/log file can be deleted(since it will be recreated automatically as dxgi). And, of course, you will also need to redirect SpintiresMod to dxgi.dll.
BTW, I've tested this and it doesn't seem to make much(if any) difference on my system. At best it seems like I might be seeing a 1-2 FPS increase with the dxgi.dll compared to with the ReShade32.dll. At worst there's no difference at all. It definitely doesn't seem to hurt performance. But YMMV.