Also having an offroad site, I too know what you are saying. With a much smaller niche (especially when you narrow it down to one vehicle type even) you start to limit yourself to who you could use for advertising. To even complicate this even more, having a local site (like we have) provides not a whole lot of constant new user traffic, but more or less the same group of people always on the site.
That isn't what advertisers are looking for, they want mass exposure to new users, not repeated exposure to the same users. So it all really does depend on your site's situation and purpose to decide the best source of income.
posted by coloradok5:
Really depends on the site content, for me Membership IS the way to go for someone else maybe not. I have noticed that car sites get much more traffic and advertising than off-road sites that's just the way it is and has been, I deal with a very small market and most of my viewers make their own parts before they would buy them anyway.