im getting to the point where i go to the track enough (yes im addicted)
2 extra wheels
and spare parts (from upgrade parts)
more helpful if you are on open track event (courses) because if you drop a wheel or something goes wrong, getting stranded a few hours from home really blows
further i go, more i'll bring.
soon my tie rods get replaced but its good to keep a spare w/ you at the track as well as a few suspension goodies.
also make sure you get some friends to go (preferebly w/ the same type of car) for extra security and backup
if its a long day, bring a small BBQ and some goodies for it.
i also high suggest a floor jack and 2 jack stands for any unexpected incidents.