Steel is my favourite by far. I spent enough time working in the fields of failure analysis and materials science to ever trust carbon fiber in an activity where the risks of nicks causing stress concentration sites are so probable. As for aluminum, my teeth are already too loose.
I'm curious how you explain all the carbon fiber mountain bikes going through unprecedented seasons and events. I know you said that you're not into racing, but in this instance, a race like the Vapor Trail 125 doesn't eat carbon bikes alive. If that doesn't, I'm not sure what would. I know several that were fine, myself included.
In a tamer environment of riding daily on not so crazy surfaces and aggressiveness, what would be the potential of carbon blowing up?
As long as the carbon doesnt get nicked in an area of high stress, all will be fine. BUT, once it does, there is little elasticity to relieve the increased stress levels caused by the stress concentration factor of the nick. Steel , as an elastic material, has a much better chance of deforming slightly to relieve these elevated stresses. Carbon fails catastrophically, steel tends to fail elastically over a longer time.
I've only ridden steal, Karate Monkey, if I ever buy a new frame it would be steal too. Even for being a "mountain" bike the Monkey is pretty smooth on gravel.
All of my current bikes have steel forks/frames. I'm building up a 29er that'll see double-duty as a gravel rig, and that bike will have an aluminum frame and carbon fork.
I've had aluminum and titanium gravel bike frames, both with carbon forks. I do not think there is a difference in ride quality. In my experience, ride quality is in tire width and pressure.
Poor downtrodden aluminum. I've been riding aluminum cross bikes for years, and my primary 'grinder is an alu 7075 cheap*ass Nashbar CX frame with a Wound-up carbon fork. The big rub on alu is always that it buzzes and has a harsher ride. I submit that most of this can be eliminated with good wheels, tires, saddle and bar tape without giving up on weight/lateral stiffness. That said, most of my road bikes are carbon. and my new build is carbon all the way. The amount of tuning that can be done to a carbon frame - if properly engineered - is better than can possibly be done with steel. While I completely agree with the concerns about carbon frames, nicks and major damage, I think the technology has advanced to the point that a properly engineered bike has enough redundant strength to withstand most failure mechanisms.
Honestly it's hard for me to tell the difference. I've rode for a long time on all materials and I really don't know that I could tell the difference if I was blindfolded and unable to hear the cables rattling on the frame so I really don't have a favorite material. I guess I'm partial to steel since that's what I started on, but I wouldn't say it is my favorite.
Chrome-moly steel all the way IMHO, but then I'm primarily a recreational rider, not a racer. I've got nothing against CF and know many riders who love it. For those wanting to get into gravel on a budget, you can put together some fine gravel mutts out of cro-mo MTBs, hybrids, and touring bikes from the early 1990s.
Steel is a really good material for building bicycles frames, because it’s light, stiff and durable. It's also easy to fix: your local welder will be able to repair a broken steel frame, although some very high-strength steels do need special handling. But try finding someone who can fix a broken carbon frame.
My two cents, all materials can make for a great riding bike if designed right. A lot of it comes down to personal preference. I've had steel, carbon and aluminum and have had great times on all of them. I would like to own a Ti bike, but they are a little cost prohibitive.
As far as durability/reliability goes. All frames developed today are tested against the ISO-4210 standard. This means that a steel frame has to pass the exact same requirements with regards to impact and fatigue as a carbon frame, or an aluminum frame.
You can expect all frames that have been tested against the ISO-4210 standard to last you plenty long to get your moneys worth out of it.
