First the brake thing. I'm only vaguely familiar with where it came from. Basically though, when people first started racing (i.e. factory teams in IMSA, World Challenge, and SS) the Calais, most of these races were enduro races. The stock rear bearings were/are not up to that punishment. I started autocrossing my car in 1990, and would routinely trash the rear bearings after two autocross events! Somewhere along the line, individuals(?) petitioned SCCA to allow upgrading the rear bearings and allowing the Saturn disks. At one point the debate got so heated, the Calais and Achieva were prohibited from racing. Don't know much more than that. Performance wise, doesn't make any difference, except your wheels won't fall off during a race. As I've told everyone who has wrote me, if you decide to not upgrade the bearings, keep a close eye on them and only use GM new parts. The autostore parts are just cheap knock-offs and will not last long at all! Maintanence is easier on the disks. Remember, the weight split on this car is 65/35. So rear brakes don't do much. If you're trail braking these cars, the inside tire is usually dragging. This item was actually carried over from the car's spec line in SSA. The brake allowance never got its start in IT (I was the first 1990 IT Calais to race).