In anticipation of a 800kms tour, mostly on good pavement, that will include 100kms of what might be loose gravel or dust. We currently ride on 2" Supreme and have had no problem on "reasonably packed" gravel roads. However, we have been unable to ride on a loose dust track, so we are considering other tires.

My inclination is to go for the Almotion (2"), which has great reviews, especially because of its rolling performance (fastest in its class). OTOH, the perspective of pushing our bikes when we hit loose surfaces, needless to say in an area where there are no services at all, including water, would suggest a tire better suited for off road riding -- the Mondial is possibly the better choice.

The problem is a bit complicated by the fact that it looks like the dusty segment is halfway on the gravel road, such that it makes it impractical to turn around if it happens to be impossible to ride.

If it helps, the road in question is the Cottonwood Canyon Road, between Cannonville and Page AZ.

Essentially, the question is whether the Mondial has a marked advantage over the Almotion over loose gravel and dust.

I haven't used the Mondial. I regularly commute on a set of 2.15" Almotion tires that I set up tubeless. I also took those tires on a 400 mile trip that included some gravel, a lot of pavement, and a lot of rail trail, including the GAP. Because of all of the time I had planned on spending on unpaved rail-trail and canal paths, I had wanted to bring my Surly ETs, which were wider and had more grip, but they didn't fit in my luggage. I plan to try the GAP again with the ETs to see how it goes, but I didn't find the Almotions to be a problem at all.

The only time I really wondered if a different wheel set would have made a huge difference was going through the Cuyahoga River Valley in Ohio along some kind of limestone/clay-covered rail trail in the pouring rain. In that situation, even my 2.15" tires felt like they were sinking into the trail surface. Not much, but enough to feel like the drag it was creating would be worse than the drag of a wider tire with better tread. But I went on, and, while I did move to pavement for a stretch, that was because I was trying to make up lost time, not because I thought my bike couldn't handle the surface.

On the whole, I haven't had an issue with my Almotions. There are certainly better off-road tires, but the Almotions make a good, all-around tire.

I wish I had some almotion experience, but a good friend of mine just finished doing a section of The Divide ride using Surly Extraterrestrial 26x2.5 over about 6 weeks and was very happy with how they handled a wide range of surfaces, including pavement.

Review: SURLY ExtraTerrestrial tires | gettingnowhere.net

in this review, they do compare them to Mondials that they had on their bikes before.

My wifes Troll came with these tires, and Ive goofed around on them a bit, but not a lot, but they appear to have a bit more aggressive treading than the almotions, and of course are much wider at 2.5inches, but in my mind, if the almotion is kind of like a "light" version , tread wise , of the ET's, they probably would work well.
For sure, the mondials have deeper side treads, but its really hard to know without riding on a given surface to know how each tire would behave.

I suspect that I would prefer the easier rolling almotions, especially as I am pretty comfortable riding on all kinds of stuff on slicker tires, and lower pressures always help. I guess the question is how much climbing on steep, loose surfaces will there be??
That to me, is the real issue, if there is a bit, but not a huge amount, then a bit of pushing is ok...but it depends on how much...

its tough not having ridden a type of tire to know how it is, and when a set of tires can cost $200, its a pricey way to find out things.
If you were in Montreal, I'd let you try the ET's, but even then, they are a diff kettle of fish to the almotions , and diff to the mondials too, especially in rolling resistance.

good luck bouncing around ideas and hopefully getting some more direct experience.

Agreed on the Almotion vs ET stuff. I pretty much decided if I were going to ride a significant amount on pavement, the Almotions would be great, and would handle the off-pavement sections as well. When I did my rail-trail/canal trail trip, it was largely off pavement, and I would have taken the ETs if I had been able. But the Almotions did fine. I haven't really considered the Mondials only because they aren't made to run tubeless, I don't think, and the tread on the Almotions seemed like a good match for the Big Bens they were replacing. If I were looking for a tubed, all terrain tire, I think I'd lean more towards the Mondial, but hopefully someone who has ridden one can chime in.