I've created an off-roading proposal over at area51, and one question has popped up regarding whether off-road cycling is on topic there. I'd be happy to say yes, but thought I'd check here first because I don't want to overlap with this site too much.
So specifically would questions regarding off road cycling (good off road routes, maintenance of bikes in this context, choice of materials for bikes etc.) be on topic here, or not really?
I was the one who brought that up on A51, and the simple answer is "yes, it's on-topic here." However, in practice, this site has only accumulated 13 questions under the off-road tag in a couple of years. And none of those are about avoiding stumps or dealing with loose terrain or posture when doing downhill runs. So we haven't done much to encourage off-road questions.
Looking at your example questions, they're almost all clearly about motorized ATVs. So perhaps there's no reason to exclude bicycles from your scope, but simply let people know that this site exists. Similarly, we might encourage questions about trail-building to go to your site. (I have a feeling you may be covering those.)
There have been bicycle questions on other sites, like Skeptics and Jewish Life & Learning, and that's a good thing. So while off-road is clearly on-topic here on Bicycles, perhaps a dedicated off-roading proposal can encourage more questions about these topics. A little overlap isn't a problem, as long as people are clear on where to ask a question. You'll need to figure out how to present this in your FAQ, as will we, if and when your proposal becomes a site. Something like "Off-road, focusing on the issues faced off-road vehicles. While we cover off-road bicycles, questions about mechanical issues or general bicycle riding might get more answers at Bicycles." But who knows? Perhaps your site will attract a new audience of off-roaders. That would be great for your site and ours.
If it's a bicycle, it's on topic here. Doesn't matter where the riding is done.
All of the questions you ask are on-topic here, though "good off-road routes" might be a little tricky to ask in a constructive fashion.
Motorcycles are not on-topic here. (motorized bicycles with pedals and a motor probably are, though) Perhaps you should make sure off-road motorcycles (dirt bikes?) are clearly on-topic on offroad.SE.
Most off-road bicycling is called "mountain biking", though there's also "cyclocross" some kinds of BMX, and other types off off-road bicycling. If you hunt around we definitely have some questions in this area already. Most "suspension" questions are really about bicycles made for off-road, too.
You shouldn't worry too much about whether or not off-road bicycling is on-topic for us. It's ok to have sites with overlapping scopes.
Better questions for you to be asking: Do people that do off-road ATVs, off-road truck or off-road SUV stuff tend to often also do off-road bicycling? Are these overlapping connected communities? Are there likely people passionate about both? Do people riding bicycles off-road identify themselves as "off-roaders" in a way that would tend to bring them to your site? Does somebody who rides an ATV or drives a truck off-road have a good likelihood of having useful answers for somebody who wants to ride a bicycle off-road? Is riding wicked single track on a bicycle anything like off-road motorcycling?
Reading through the current example questions I don't see any questions that apply to bicycles at all. Maybe the tire question.
