The degradation of the microstructure is registered and corre- lated to the hardness change measured. Material at larger depths below the wheel tread surface experience slower cooling in pro- duction, which gives a decreasing hardness with depth. To extend the validity of the results for a wider range of heat treatments, or depth below the running surface, hardness was measured and correlated with microstructural parameters examined by scanning electron microscopy and optical microscopy. Specifically, the fer- rite content and lamellar spacing was measured at different depths for both undeformed ER8T and ER7T.