I'm willing to accept evidence either way - if Hoosier is designing this thing with lower block height, then they must have some reason to think it works.
I was just hoping you'd have some technical backup for saying the tread depth is so important- because I think it's perfectly reasonable to think it'd be possible to get good performance with less depth.
edit: in most cases I've heard of tread depth being important are mostly related to maximum performance stopping, or when something is stuck and you need to dig out - most rally driving on gravel, aside from the start, is a lot of lower wheel spin scenarios-
I've got a fairly decent ability to read and understand technical material, so if you can explain what's supporting your idea, I'd appreciate it.
Unfortunately, white papers on rally tire development are few and far between. All I have is anecdotal evidence, combined with the general knowledge I've been able to dig up and figure out about how a tire in a loose surface situations functions. I'm sorry if it came off as "attacking" you in that last post, your response to my initial question seemed like you had something to prove? I don't know, but I apologize.
The long and short of it is that the mechanical grip (created by the edges and voids in the tread) is what creates most of the traction in offroad situations (I'm just stating this, I am sure you know this). Sure, there are definitely hard packed types of surfaces that do utilize the compound of the tread more (obviously, the reason why manufacturers offer different variations of how "tight" the tread pattern is to get more rubber on the road to get more grip from the compound).
What does this have to do with the "depth" of the tread block though? Well, as mentioned, I've never heard or seen any rally drivers claiming that worn out tires are faster. Ever. As such, you may be right that there is no inherent difference between a tire with fresh, sharp blocks, that has a tread depth of 12/32" (pulling # out of my ass, not at the shop right now) vs 8/32", all things being equal. But what may be an important factor is that relative to the wear produced depending on the varying compounds, you may run out of the necessary amount of tread while on stage. Hence more = better from that perspective.
So in some ways, I suppose you are right; if a team had an unlimited budget, and could be guaranteed to know exactly what their tire wear was on any given stage, they may be able to shave a tire for maximum performance, while needing to maintain the necessary minimum tread depth for best grip. Again, while theoretically possible, this throws a whole bunch of variables out the window. We don't see WRC teams shaving tires (maybe there is a rule against it?), but I have my doubts that it is feasible, or worth while. Overall, as offroad tires utilize the mechanical grip generated by their edges, compound is secondary. If the tread depth is too little, this causes multiple issues (the tire not being able to bite far enough into the ground to get maximum mechanical grip, the tire not being able to clean itself out properly, etc).
Hoosier is clearly a company that knows what it is doing in the asphalt world. And I would argue that very little from there applies to what we are doing. Your assumption that they know what they are doing, is counteracted by the fact that they've never done this before. They may have made a mistake and not realized it. Considering people would have been testing on brand new tires all the time (to control for variables and if at events, to get the best results), they might not have realized this mistake. Or they've dialed in their compounds juuuuuuuuust right such that they can make better recommendations for surface and temp without destroying the tires too soon.
Maybe we find out that their tires are too narrow "variable-wise" to handle everything a rally can throw at them and they work great in only specific circumstances? Or maybe they have found out something that massive multinational corporations like Michelin and Pirelli haven't found out (seems a bit of a stretch).
Full disclosure, I brought in and sell Federal's line of gravel tires. Having ran on every tire available, I was quite impressed with them. Are they Michelins? No. But they also aren't $400cad each. Interestingly enough, a lot of comments were on how aggressive/deep the tread looked relative to dmacks and pirellis. I personally found overall grip to be higher than the dmacks, even on surfaces that were very hard packed (Rocky and PFR are both in the mountains, giving a somewhat comparable test). The Federal's have a very defined, sharp outer edge block, unlike the rounded one of the pirellis and dmacks.
The reason I bring that up, is further backing of the tread depth/shape of the tread vs compound. I haven't noticed much wear differences between comparable compound tires. Soft pirellis seem more like what I consider a medium, with dmacks softer, and the federals softer still. It seems to me in my experience that compound selection in rally is more about temperature (too cold with too hard a compound = chunking, too hot with too soft a compound = burning rubber off too quickly).
At least we are having an interesting conversation. I doubt you'll find anyone with any extremely technical information. Hell, engineers are taught in school incorrectly how a tire functions in reality (boy oh boy do they have it down in theory though haha). You can see this in testing done and some of the engineering forums online where people argue about tire concepts and designs.
Edit-
I just realized I should note, that of course hoosier has YEARS of dirt-track experience. Again, I don't think that really applies to rally. Very different surfaces, circumstances, and design of the cars.