DeoreDX

I entered a 60 mile gravel race and I don't actually own a gravel bike. I do own a Salsa Mukluk fat bike that I have built a set of 29" wheels for that I run with 29x2.5" Surly Extraterrestrial tires that I use as my do it all adventure bike. It's not fast (very upright position, heavy 1kg tires) but it's like a cross between a Cadillac and tank show and just plows over everything. Doing 60 miles on her isn't an issue. Doing it with speed an efficiently is. It's a far cry from a gravel racer and feel like I'm pedaling in quicksand in comparison.

I've slammed the stem to get a little more aero but I'd love to get some lighter faster running tires. The 30mm id rims are a problem though, I'm not sure how skinny of a tire I can put on them. I'd love to hear some tires suggestion, make/model/size that might work well for me. I'm worried about tire profile getting too square if I run anything smaller than a 2.1-2.2. I am running tubeless if that matters.

msu2001la

For reference - 2.1 inches is 53mm. You can go much narrower than this.

Are the rims hookless? Regardless, I think you could safely run something like a 38mm on a 30mm i.d. with no problems. You might even be able to go down to 35mm assuming you're keeping the tire pressure reasonable.

38mm Gravelkings are popular for mixed surfaces. If you don't need tread, you could check out Rene Herse - The Barlow Pass (also 38mm) likely checks all the boxes for you. It's light, fast and tubeless ready.

DeoreDX

The rims are hookless. With respect to width coming from the mountain bike background I know some mountain bike tires with the cornering knobs get a little weird when running on a narrower rim. Of course with a front fork wide enough to fit a 5" tire it will look a little strange

cellery

What you want is supple, slick to semi-slick rubber that allows for easy sidewall deflection and a contact patch that stays planted on hardpack. No big side knobs, no deep sipes. Just a no nonsense piece of flexible rubber, high TPI bigger than 44mm and smaller than like 2.2". The person above you might not be wrong that you can go down to a 38mm and probably be ok. The question is why would you? This will incur substantial suspension losses for a harsher ride, which makes you slower. The weight thing with tires has all but been disproven. As long as you're not going far past the width of your downtube, you're not incurring statistically significant aerodynamic liabilities. I'm as fast & efficient on 2.3"s as I was on 25mm tires - on pavement even. The real concerns are aerodynamics on such a bike and the wide range gear jumps of a mtb drivetrain which may be detrimental on the flats, but possibly a benefit on the climbs. I'd look into the following brands for tires - Rene Herse, Ultradynamico, Terravail, WTB - go with their most race oriented casing semi-slick. And then buy some clip on aero bars. Worry about getting into a 2x gearing if you get into serious racing.

tangerineowl

They're not exactly a modern 'gravel' tyre, but I run the 2.2 SpeedKing Racesport tubeless quite a bit across road and mild gravel. About 460gm.
CST does a 550gm? 2.35 Control Beach. Around 60mm across.

Being fairly light tyres for those widths, they do have supple/thin casings; so how they'd hold up in a race situation across certain surfaces would be the luck of the draw perhaps.
On road, the SpeedKing is pretty fast.

Once heading in the direction of a tyre with more grip i.e. knobs, there are a small number of -once again- supple and fairly light options at 2.2/2.4+.
The Kenda Sabre Pro [in TR model] being one. Similar tread to the ThunderBurt.

Keep heading down the knobby path: more grip at more weight, and on a downhill rolling resistance line.

Conti RaceKing comes in a Racesport casing, but not sure if in bigger widths.

Polaris OBark

Take a look at the Rene Herse website. They have two specific tires made by Panaracer in a variety of diameters and widths up to 55mm, and four different casing strengths. I like the EL (extra lights) the best, as they are the most supple and enjoyably efficient to ride, but if you need puncture protection, there are more durable versions as well. I've got some of their 700C x 55mm Endurance Plus tires, both slick and treaded. They are a bit more ponderous, but might be what you would prefer.

Eric F 

Efficient rolling, and still some good grip for cornering in the dirt...45mm Pirelli Gravel H (rear) and M (front). On a 30mm internal rim, they will probably measure a few mm over sticker. They're also very durable.

dsaul

I have a set of Terrene Elwood tough 700x40 tires mounted to some 29" 30mm internal MTB rims and they work great. I originally built the wheels as an alternate set for my 650b plus bike and never used them, so they got repurposed for one of my gravel builds.

Clipped_in

I ride Pirelli Gravel H 40's front and rear on 25mm internal hookless and I like them a lot. I have about 5k miles on them. Easy to recommend.

Eric F 

If they suit your terrain, they're a great choice! I really like the H/M combination for my local area because I like the grip of the M on the singletrack that spices up my local rides. I've used the H/M combination in both 35mm and 40mm. Right now, I'm using 36mm Challenge Getaway Pros. They roll as quickly as Pirelli H, and have almost as much cornering grip as the M...and they're lighter.