Friction　materials　play　an　important　role　in　the　safety　of　automobiles.　In　this　work,　we　study　the　effects　of　graphene　oxide　and　alumina　with　different　mass　ratios　of　micrometer-sized　alumina　to　nanometer-sized　alumina　on　tribological　behavior　of　phenolic　resin-based　friction　materials　by　friction　tests.　The　experimental　results　reveal　that　the　structural　stability　of　the　friction　materials　is　dependent　on　the　mass　ratio　of　micro-sized　alumina　to　nanometer-sized　alumina.　The　friction　coefficient　varies　in　a　range　of　0.60–0.63　for　the　materials　with　high　fractions　of　micro-sized　alumina　over　the　temperature　of　100–350　°C　and　in　a　range　of　0.4–0.5　(i.e.,　thermal　recession)　for　those　with　high　fractions　of　nano-sized　alumina　at　350　°C.　The　wear　rate　of　the　material　without　graphene　oxide　is　within　0.13–0.36　×　10−7　cm3/(N·m)　at　100　°C　and　within　0.5–0.7　×　10−7　cm3/(N·m)　at　350　°C.　A　compromise　needs　to　be　taken　between　the　friction　coefficient　and　the　wear　rate.　For　wear　at　low　temperatures,　increasing　the　fraction　of　nano-sized　alumina　in　the　total　alumina　powders　reduces　the　wear　rate　of　the　friction　materials.　The　wear　at　temperatures　higher　than　or　equal　to　200　ºC　can　cause　the　formation　of　friction　film,　which　can　alleviate　wear　and　improve　the　friction　performance.　The　tribological　performance　of　the　friction　materials　with　graphene　oxide　deteriorates　with　increasing　the　fraction　of　nano-sized　alumina.　The　optimal　performance　of　the　friction　materials　is　achieved　with　the　mass　ratio　of　micrometer-sized　alumina　to　nanometer-sized　alumina　being　13:5.　4-layer　graphene　oxide　is　preferable　over　8-layer　graphene　oxide　for　the　enhancement　of　the　wear　resistance　of　the　friction　materials.　©　2025　Elsevier　Ltd