I'm giving a general answer that would apply for anyone with this sort of question.
Series organizers use a couple different methods of organizing their events.
Some use one massive thread, which shows all the details for all the races (Typically in the first few posts) and then houses all of the race specific AND general series related discussion, under one roof.
Others use individual threads for each separate race event.
Under the second scenario, general series discussion can be both a bit off topic and fragmented, since it will be spread across several threads.
I could see a case for having a general series discussion thread IN the
Racing Series Forum, in the event you are managing your series with individual threads for each race.
If you just have one big thread, no need to create a separate thread for discussion, particularly if the intent is that the discussion will be off the topic of the series.
In your specific case, it's going to be more of a general discussion for series participants (aka team members). I would put the thread in the
Clubs and Leagues section.