we don't intend to intermix monster trucks with street cars. we can break things down as much or as little as you guys think will work best.

the example about the radio questions shows that too many forums can sometimes inhibit getting answers but makes things easier to find.

Many forums = easier to find
Many forums = fewer answers and less interaction
Fewer forums = harder to find
Fewer forums = more answers and interaction

so the tradeoff is always how many forums you break things down to in order to make things easy to find but not inhibit the activity.