This may be mentioned elsewhere and there also may be alternatives but this improved the gfx detail in MXB for me.
MXBIKES DPI GFX FIX (GFX detail enhancement for MXB - eliminate pixelated effect)
1. Go to your mxbikes.exe file wherever you installed it on your HDD or under Steam C:\Program Files (x86)\Steam\steamapps\common\MX Bikes.
2. Right click on your mxbikes.exe file and select Properties\Compatibility and click on Change high DPI settings.
3. Tick the box for Override high DPI scaling behavior - Scaling performed by choose "Application" then Ok - Apply - Ok.
4. Enhanced detail for MXB sorted. Run game (turn off shaders for increased fps if you have shaders installed - F7/HOME).
5. Run game.
Alternative suggestions welcome.
TM_Infidel
www.tmfactory-racing.com
Well I'll be dammed... A TMFR guy on the MXB Forums