Originally Posted by TimR
How are cars classed in track days? Are they similar to auto x?
Depends on the type of track day.
Some clubs are driver-ed classes only. The run groups are divided by driver experience, and to a lesser extent, the capabilities of the car. There is no competition, and as such, no "class".
Some clubs are a combination of driver-ed and time-trails. Time trials are similar to autocross in that the competition is gauged by laptimes (ie: fastest lap time in a particular class wins that class). Like autocross, the competition is basically you, your car and the track against the stopwatch. That makes it sound much more tame that it actually is, but that is effectively how the competition boils down.
The driver-ed portion of the TT event is similar to other clubs, where run-groups are divided by experience (licensed high-power cars, licensed low-power cars, intermediate students, novice students). The time-trial practice sessions are divided by competition class. The time-trial competition sessions are either divided by average lap times or car class, depending on the club/organization.
Each club has its own rules. The rules will be much more similar to SCCA road-race classes (Showroom Stock, Improved Touring, Production), and not
SCCA autocross classes (SS, SP, ST, etc).