|What gravel looks like, for reference.|
That is to say, I've ridden my fair share of tires, and there are a few things that make a tire "good" in general. You can guess the first thing- weight. No one wants to spin up a big, heavy tire, especially up a long grade. The other thing that is apparent to many riders is the way the tire's casing "works". In other words, is the tire supple, or does it ride like a solid rubber chunk of crap? (This affects more than just ride feel, by the way.) Then there are the finer things, like traction, cornering, and braking performance. Basic stuff that if it is good, makes or breaks a tire's reputation.
That seems simple enough, right? Get those three basic areas "right" and you can't lose. However; it isn't all that simple. Obviously. That's why we have a gazillion tire choices. If "one" thing worked for road, and another for "gravel", and another "one" thing for mountain biking, well, there would only be three tread patterns. That's laughable to think about, in light of reality, because we have a confusing array of tires for every different situation. Too many choices. Somewhere between "three" choices and a "gazillion" is where the truth lays.
There are a few things people get wrong when it comes to bicycle tires, and the most egregious thing, in my opinion, is when people try to tie the attributes of motorized vehicle tires to bicycle tires. While there are a few obvious parallels, the comparisons are like comparing a deep sea fishing rod to a Tenkara rod. Similar in some ways, yes, but the design intentions and performance parameters are so different that the only remaining similarities are in basic form and name.
|They say you don't need tread on a gravel road going tire? Hmm.....|
In the gravel going arena, I find that a tire totally devoid of tread isn't the very best idea, and neither is one that has all sorts of tread on the casing. Just like with the tread design choices, there is a middle ground somewhere that actually works well. However; it is something else that also needs to be there, which if not included, will make or break a tire's performance on gravel roads. That is the casing's shape, or the way the casing and the tread form a shape which hits the road.
In all of my gravel miles, the tires that perform best seem to all have a shape which isn't really "round" in cross section. Something "less C shaped" and more squared off or flattish seems to really tame loose stuff. You can get there several ways. Sometimes air pressure and rim width can do this. Sometimes tire design gets you this trait, and many times a clever use of smooth and treaded design in the right spots gets you there. Many times bits of all of the above come together to get a tire which rides wonderfully on gravel.
The thing is, a "standard", roundish shape tends to plow, like the bow of a boat, through looser gravel. This is most evident when tire pressures are too high. The resulting ride is not unlike a skinny tire on gravel. There is a lot of vibration, lateral movement, and the rider has to correct the front end much more than one should. I call it "herding" the bike instead of riding it. A tire with a flatter profile, maybe with lateral tread blocks on the sides, gives the tire an ability to float over gravel, and the flatter profile also cuts way down on the "bow effect". There is a lot less "herding" the bike and far more riding it.
So, maybe you have a different idea? Fine. That's why they make a gazillion different tire choices.