I do a few trackdays, and my car is pretty much standard. Unless you're entering racing championships you don't need to go too overboard, track sessions are about fun, and as my car is a daily as well I need it to ride well everywhere.
Mine has:
Standard discs, pagid pads, dot5.1 fluid
Toyo T1-R tyres
Cold air feed from passenger fog to air filter
Cold air feed from drivers fog to power steering reservoir
Lowered on Eibach suspension
12.5mm rear axle spacers
I stripped the back end of the car out for my latest session at Combe and it felt different, unsure just how much difference it made to cornering.
Make sure your fluids are topped up, tyre pressures are OK, and have fun. The ST is a very decent handling car out of the box, very little has to be done to make it better. At Combe earlier in the month, there were a number of standard ST's out on track having a laugh
