How to change a kart's performance on a certain terrain

[LolaB09/60fan124]

I'm trying figure out how to change a kart's max speed on certain types of terrain. I already know one way do this is by changing the max speed from the materials.xml file. The problem with this is that changing this affects ALL karts. Is there a way where I can create characteristics that affects a kart 's max speed on certain road types individually? For example, Tux is faster than Xue on sand, but Xue is faster on ice.

[QwertyChouskie]

I don't think there's a way to change it per-kart, since max speeds are set in the texture's settings. Changing it to work on a per-kart basis would require significant rework of much of STK's code and assets.