frontrangegravel
Gravel Grinder News shared this good discussion about tires.
How wide is too wide for you? What do you normally run?

Read the post here.
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GRAVELBIKE
Much of my unpaved riding takes place on 25, 28, and 32mm tires with minimal tread. If I need anything wider than a 35, I'll generally grab my 29er.
GRAVELBIKE.com - ride everything
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DustyRhodes
For years I thought a fatter, heavier tire at lower pressure was obviously slower.  That was until I got a 29er with Racing Ralphs setup tubeless.  They roll surprisingly fast on pavement or smooth dirt.  I think the fast roll is due mostly to the very thin supple casing. 

I am in the process of building a gravel specific bike and plan to run 42-45mm tires with the idea that I can run lower pressure (versus a 32mm) and get a softer ride with no significant speed penalty.
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BluesDawg
The 1.8" (44.5mm actual) Specialized Renegade tires I run on my BMC Monster Cross do such a great job of smoothing gravel roads that I can ride faster and more in control than with 35mm or narrower tires. I had similar results with Vee Rubber V-12 1.95s at 47mm actual. They also float better on loose gravel or sand. I can ride these roads on 28mm tires, but the ride is harsh and steering is less precise. There is a small speed and noise penalty on pavement, but that may be more due to the moderately knobby tread than the width. The 40mm Clement MSOs on my Crux run nearly as smoothly at lower pressure as I run them tubeless.
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DustyRhodes
BluesDawg, what pressure do you run in the 40mm MSOs?  I just bought a pair and planning to ride for the first time on Sat or Sun.
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BluesDawg
I usually run  the MSOs about 30 front and 35 rear, a tad more if I'll be on much pavement. I needed about 10 psi more than that to avoid pinch flats when I ran them with tubes.
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Pattersnap
I'm also a fan of the 700x40mm Clement MSO's for heinous, Flint Hills-type gravel. Around the Front Range of Colorado I use the 700x35mm Clement X'Plor USH. I run both setups tubeless on Iron Cross wheels.
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drwelby
If you want fat and fast, the Resist Nomad 700 x 40's are the ticket. And they're remarkably cheap. No tread, so they don't work so well in the mud, but when it's dry you're not dragging a bunch of knobs through the air.
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