On that note:
Mine is a Chinon CE-4 (uses Pentax K-mount). I have a Pentax 50mm, a Sun 70-200 f3.something, and a 28 by someone else. All are decent, not spectacular, glass. I don't use the 28 nearly enough.
I just got a 2x multiplier to try on the Sun, 'cause as bella noted, you're not very close to the cars when you aren't credentialled.
I'm on the incremental upgrade program, and since I have a (hopefully repairable) Ricoh as well as this Chinon, I'm staying for now with K-mount lenses. I'm still trying to get the most out of the equipment I have, before I start pouring
serious money into new equipment.
As with my other long-term motorsport goals, all this changes when I win the lottery.
(Oh, wait, you have to actually buy tickets to win, don't you?)