CassidyAce
Senior Retro Guru
Can the definition be broken down to a list? Not really.
Is a list of defining features counterproductive and unhelpful? Not really, either.
I don't think that you will find a single feature that all mountain bikes have that other types of bike never have. Fat tyres? No. Fat bikes, jump bikes and even the Raleigh Chopper had fat tyres. Nobbly tyres? No, CX bikes, gravel bikes and, again, fat bikes can have those. Wider handlebars? No. Well, it depends on what you call wide, but a modern hybrid or flat bar gravel bike might have relatively wide handlebars. And, in any case, some 90s' mountain bikes had their bars cut pretty short.
What about a feature that all mountain bikes have, regardless of whether other types of bike have that feature sometimes? Arguably, not even that. If I put skinny tyres on a mountain bike, I still think of the bike as a mountain bike, just one with skinny tyres. What about two wheels? Surely, all mountain bikes have two wheels. If there was just one wheel, it would be a unicycle, and if there were three, it would be a tricycle. However, it's debatable whether even having two wheels is a defining feature of a mountain bike. After all, if I see a mountain bike with a wheel missing, I don't stand there wondering what on earth this alien object is before me. I know it's a mountain bike with a wheel missing. Take away any single component, and I could still make the same type of comment However, take away all of the components and I would no longer say it's a 'bike' so much as a 'mountain bike frame' (and forks, perhaps).
So, can I define a mountain bike (or much else, for that matter) with a list of features? Not really. However, despite all the changes that mountain bikes have gone through, I can still identify a 'mountain bike' very reliably. It's not a meaningless phrase. What defines a mountain bike, then? 'Family resemblance' and 'lineage'. Although I cannot produce a list of features that all mountain bikes have, I could produce a list of features that they tend to have. If I listed ten features, I might find that bikes identified as mountain bikes have, roughly, seven of those features. They don't all have the same seven features, but they tend to have seven features drawn from that set of ten. That's family resemblance. A 'mountain bike' is not a sharply defined concept but that does not mean it's a useless concept. It's good enough for me to say that a hybrid bike has some mountain bike features, or that it is like a mountain bike to a greater of lesser extent. What about the changes in mountain bikes over time? Today's MTBs are very different from those of the eighties and nineties. That's where lineage comes in. That's the gradual development of design over time; the slow shifting of the cluster of features that MTBs tend to have. Some things are added and others are taken away from the set of features which mountain bikes will have seven (or whatever) of, just like every single atom in your body, and the way you look, will change over your lifetime but you can still be identified by your history/biography.
There you go (and thank you to Ludwig).
