We investigated the spacing dependence of recording characteristics on head-medium spacing due to the surface roughness of substrates. CoCrPt-sputtered tape media with a magnetic thickness of 25 nm were deposited onto polymeric substrates possessing very different roughnesses for this investigation. The degradation in the write and read processes due to spacing was a significant limiting factor at high densities. By utilizing smooth polymeric substrates, a substantial improvement in system bandwidth as well as effective write field gradient can be achieved. As a result, overwrite performance was also considerably improved over the frequency range of interest.