[BadAssGSR]

Lowering the psi on your tires can "soften" up your side walls. This gives your tires a bit more time to grip the pavement by letting the side walls flex, hence better track times. Lowering the tire pressure can also prevent any kind over-inflation that you might have done on your tires. And we all know that over inflating your tires = less contact patch, so lowering the psi can also yield better track times.