Donnelly started life as Clement, which is a name that they licensed from Pirelli. When Pirelli entered the bike market, Donnelly decided to rebrand as Donnelly and end the license agreement. A whole whole lot of people were exposed to Clement/Donnelly through their PDX cross tires, which were on roughly every other bike at the races 7 or 8 years ago. Even several years after the name switch, I wind up explaining it when I talk to people about their tires, which is why I start with that here.
I am certainly not the world's foremost exponent of gravel riding. If there were more opportunities to do it right from my door, that would change that, and I would love it if there were, alas there are not. But this week I am in a place (Block Island) where if you are creative, there are ample opportunities to ride gravel. I'm using RCGs with Aivee MP4s as the test wheels here, on my 10 year old HOT BUNS disc cross bike. There's room for a slightly bigger tire in the bike (for sure in the front) but these fit comfortably. 36 is right about the tire size where if you are starting from scratch you might consider using our wider All Road wheels, but RCGs are a great match for "narrower" gravel tires like these because of the increased suspension. For my current more than 165 and less then 170 pound body weight, I inflate them to 40psi.
The gravel roads particular to Block Island are sandy and rocky - this is not the land of loamy hero dirt. It's also one short hill after another. Some of the pave roads are flat, but none of the dirt ones are. So the big issue is traction, and have these got it? In spades, they do. Being just a little smooth about it, you can go from in the saddle grinding to full torque standing without worrying about washing out your rear tire. My aging corpse and high deductible medical insurance prevent me from sending it as much as I would like, but downhill cornering confidence from the front tire is huge.
That level of traction is no surprise when you look at the tread. It's aggressive. The surprising standout traction situation is the sandy paved road corner. These are great at it, which is clearly the wide-spaced but relatively tall side knobs. "Loose over hard" or any approximations of such usually send me into shivers of dread, but these are good at it.
In deep sand, they stink. No tire this narrow is going to be any good in deep sand. If you ride loose, you can float through sand patches without inducing terror. Deep sand is where you want a fat bike.
On the road, the traction is excessive. You won't be doing a whole ton of coasting. There are tires, Schwalbe G-One Speeds in particular, that you can easily use in a group ride at minimal handicap and then turn onto a dirt road and they work great there, too. But I wouldn't expect a G-One Speed to have the kind of traction these have on loose 12% climbs; you'd need to be much more careful with rear wheel management on G-Ones than you do with these. Everything has trade-offs.
One thing I dislike about these tires is that the tread isn't super straight. The first time I used a (then-Clement-labeled) BOS tire, it had a tread jag so bad that I had to replace the tire. It was so distracting. This one has a much smaller version of the same issue, but it's still distracting. A lot of brands get this right consistently, and they all should.
The casing isn't nearly as supple as Renee Herse or other "let's make these tires ride crazy nice" tires, but that should pay back in some durability. Renee Herse (nee Compass) tires are consistently spectacular to ride, but they sure don't last forever. These inflated easily and haven't leaked any air. I used Orange Seal sealant, which I don't think has yet come into play.
The eagle-eyed among you will note that my bike is not exactly cutting edge. The frame is old, the brakes are BB7s (which I've gotten to work perfectly over the years), it's an all-SRAM drivetrain but I couldn't for my life tell you which parts are what level, though I do know that the levers don't match. It has quick release dropouts, even. I have road pedals on, which is probably the wrong choice but oh well. The wheels are awesome, though.
I normally go for centerlock hubs, but these Aivee MP4s fell into my lap and so I used them. Roughly 2000 miles into life, they're great. I'll open them up before too much longer and see what's gone on inside, but they work wonderfully. If you're looking closely, I also have alloy nipples on these wheels. Normally I go brass (silver brass, to be precise) but a 10 year old black bike needs a bit of pizzazz and the neon yellow and blue scheme (it's an homage to one of those Belgian teams that always rides like life depends on it in whatever World Tour races they get invited to) came together well and I like it.
One decidedly highbrow thing about this bike is the Arundel Mandible bottle cages. I will not be swayed from my opinion that these are the world's best cages. They're secure, they look great, they don't scratch your bottles, and in the 5 or 6 years I've used this pair I've never thought about them except to think "man, those are some awesome bottle cages!" Expensive, though.
So, to the original point, the MSOs are great tires if you need more traction and less road speed. The 36mm size works great with the 21.5mm inner width of the RCGs. If you want a set of tires dedicated to dirt and gravel riding, these would make a great choice. Pressed hard for more crossover duty with road, the tread is a bit much.