Dec 2021, 44mm slicks was ridable. This is a jeep road with lots of baby heads in spots.

In July 2021, I attempted Mt Easter/Clay Bed Road on a gravel bike with 38mm tires. Large stretches were not rideable due to the sandy terrain (no traction/sinking) combined with huge carved gulleys across the "road" (really more of a sandy Jeep trail). I would say that a fat bike and a strong rider willing to push through sand would be most appropriate for this terrain. If you are expecting terrain similar to the other gravel roads in the region, you might be in for a surprise! Unless you read this comment. FYI: I'm an experienced rider. I was on an 80 mile gravel ride that day with 7000+ feet of climbing that day. Getting through this section was way harder than anything else I did that day!