Mountain bikes, and their riders, are not generically a problem. It is the the subclass called "freeriders" that are a menace. They have made impressive advancements in suspension and brakes, as well as the protective gear, but that has only encouraged an outlaw attitude.
They are now capable of traveling downhill at speeds that used to be unfathomable, especially considering obstacles, but it is entirely unsafe for other mountain travelers - including fellow bikers that may have different equipment, and/or may be traveling uphill. And their attitude towards the bear bells is that they are a warning for you to get out of their perceived right of way, so if they have a bell and you get hurt, it's your own fault.
The Forest Service has tried to crack down on these guys (yes, only guys - which tells you something), especially in areas like Sunset Ridge (Millard Canyon) where they really tear up the trails. There is a CFR (Code of Federal Regulations) law against "destruction of resources". The rangers have tried to "pull over" the bikers to ticket them, but since the rangers are on foot at the time, the bikers just give them the finger and ride on. ANF management has half-heartedly tried to bust the guys making money from driving the bikers to places like Mount Wilson, because they are operating a business within the forest boundary without a permit, but they just keep coming.
Now, here I'll tell you a thing or two with this preface: my fat ass has planted itself on a mountain bike seat many a time in the San Gabriels. First on my '92 Marin, secondly on my '99 GT, then on my '05 Gary Fisher, which I still have and love. I do enjoy mountain biking and exploring the San Gabes as such. But these "freeriders" have got to be stopped!
It's nerve-racking enough to see 10 or 15 dreadlocked guys (and you know who you are) headed towards you at 40 MPH, but when you add eight to ten loaded donkeys to the mix, it's downright terrifying! On those occasions, I couldn't care less about the obnoxious bike rider, but they were jeopardizing the lives of the animals, and the livelihood of many people.
The most annoying thing about these guys is (cover your ears kids) not the fact that they are inconsiderate and dangerous assholes, it is that they are pussies! And I have told them so to their pussy faces as they would ride away from me and my pack string. THEY DON'T EARN THEIR RIDE!!! Some joker with a van trucks them uphill and they just coast down. I don't see why they need pedals - just some pegs would do - because when they get to a hill, they all get off and push the bikes! They're not even in good shape because my fat ass, pulling six or eight other fat asses on a rope, has caught up with them as they lug those big-geared monstrosities uphill.
I can't tell you how many times I wanted to put a hiking stick through the spokes of one of these freeriders. Well, it was about the same amount of times that I thought of spilling roofing nails, putting carpeting tack strips under leaves, stringing up piano wire, excavating tiger traps...
The good bikers are over at CORBA - Concerned Off-Road Bicyclists Association (
http://www.corbamtb.com/)
A solution might be here...