I agree that *in general* many driving questions would be off-topic for a "Maintenance and Repair" site.  However, I think there is a certain subset of these questions which may be more relevant, and perhaps warrant some special attention.

This question is a good example:

http://mechanics.stackexchange.com/questions/21/rear-brake-on-motorcycle-closed

Although it runs afoul of some general [StackExchange "good subjective/bad subjective" guidelines][1], I think it could be a salvageable question.  The reason it is relevant is because it does relate to a mechanical component of the vehicle, and the reason it deserves special attention is because it seeks to address the proper and *safe* operation of the vehicle.

While this site's primary purpose is to cover "Maintenance and Repair" issues, I would suggest that issues that relate to the safe usage of mechanical components also be on-topic.  I'm sure there's nobody here who will disagree that safety should be a primary concern of any driver on the road.

I think that individuals who are experts in the mechanical functions of a vehicle's safety features would be the ones best qualified to answer questions such as these.  In fact, I would almost go so far as to say it would be irresponsible of this group to ignore such questions when they can be appropriately answered here.

Additionally, consider this question which is not at all about any mechanical part - nor any part of an actual vehicle, for that matter - and yet it has received a few decent answers, no down-votes, and no close-votes:

http://mechanics.stackexchange.com/questions/28/preventing-visor-from-fogging

Despite being otherwise irrelevant to the topic of this site, the question seems to have been welcomed as it is relevant to the safe operation of a motor vehicle.

  [1]: http://blog.stackoverflow.com/2010/09/good-subjective-bad-subjective/