Difference Between an IROC-Z and a Z-28 from the same year

First of all, this was only possible for years 1985, 1986 and 1987 because these were the only years that both the Z28 and the IROC-Z were made. In other words, 1988, 1989 and 1990 had only the IROC-Z model, no separate Z28was available. But it is a popular question that I will try and answer here.

The IROC-Z was available as RPO option package B4Z and was added to a Z28 to get an IROC-Z.

As a result of having the B4Z upgrade, the IROC-Z had lower ride height than a Z28 and featured performance-calibrated front struts and springs.

The IROC-Z came with Bilstein rear shocks and 16 inch aluminum wheels.

The IROC-Z standard tire size is 245/50/16 which is larger and lower than the Z28 tire for the same year.

The IROC-Z, because of the suspension enhancements, produced skid pad numbers of around .89 to .92, which blew away any mustang numbers on the skid pad.