I made these hubcaps with a new normal map, but when I spawned it in, the hubcaps would have a extremely weird reflection.
The normal map itself seems to be doing nothing Blender with normalmap: Blender without normalmap: Also, we use DXT5_NM for normal maps (Different from DXT5). Have you tried ingame without the normal map? (ie. comment out the normal map from the materials.cs and reload the game).
In GIMP you have to choose BC5/3DC (which is equal to DXT5NM) https://www.garagegames.com/community/forums/viewthread/138319