Thanks, Henry Highrise and cboy.
No smoke? No flames? I must've done something wrong.
I left out one that I've seen suggested several times: Health - Safety. It could be argued that such discussions are specific to one of the other categories, instead of separable.
The expansion and accumulation of information that almost fits existing categories is what worries me. You can find threads that cover the same topic but which are posted in different fora. Jon's Knowledge Base project attempts to index the growing mass of information, but it shouldn't have required as much work as it apparently took.
Given a basic breakdown of:
1.1. Chassis - Running Gear (things which make it an automobile; things that make it go, stop, steer and carry a payload)
1.2. Body (the payload carrier; things beyond its possible functions as a chassis)
1.3. Electrical (the auxilliary power system; things that handle electrical power that is not used to make it go)
1.4. Garage - Tools (the hotrodder's lair and magic wands)
1.5. Hotrodding Basics - General - Miscellaneous (things that don't fit the above)
It becomes easier to decide where a given discussion should be placed. Making that decision easier also results in better self-sorting. When someone has a question, especially one with some frustration already built up, it should be as apparent as possible where that question should be asked. Ambiguity leads to more frustration, more work for mods, more work to find answers, more disorganization (more miscellaneous).
Using those basic categories, it becomes easier to accommodate expansion. For example, if the Engine discussions start piling up, it might be subdivided like:
184.108.40.206. Engine - Mechanical
220.127.116.11. Engine - Electrical
18.104.22.168. Engine - Fuel - Intake - Exhaust
22.214.171.124. Engine - Cooling
Likewise for, say, Body:
1.2.1. Body - Exterior
126.96.36.199. Body - Exterior - Fabrication
188.8.131.52. Body - Exterior - Repair
184.108.40.206. Body - Exterior - Prep and Paint
Starting with broad categories that are chosen to match the major functions and component groups of an automobile, and then subdividing those, helps avoid large organizational changes as the information accumulates.
Reorganizing due to growth becomes easier because the overflow that necessitates the reorganizing would already be contained in the proper major subdivision.
If hotrodding evolves to mostly unit body vehicles, under the present structure of hotrodders.com, you could end up with thousands of threads about the structural aspects of the body mixed in with thousands of threads about painting, all in Body - Exterior. With the structure outlined above, those structural threads would already be migrating and accumulating in 1.1.1. Structure - Frame or Unit - Fuel storage.
Consider a growth in alternative power hotrodding. If somebody develops a battery today that stores the equivalent energy of 10 gallons of gasoline in the same or even double the weight, you can bet some hotrodder is going to make use of it. In the present organization structure, would discussions of mounting that battery go under Electrical? Doesn't really make sense, but that's where those would probably land. Using the suggested organization, discussions about the mounting of the new super battery would go under 1.1. Chassis - Running Gear, specifically 1.1.1. Structure - Frame or Unit - Fuel storage.
You can't really anticipate where the hobby might be taken by hotrodders, but you can bet that every vehicle that every hotrodder tinkers with and mutates will have to go, stop, steer and carry something. You can also bet that hotrodders will continue to need tools and a place to work their madness.