2018 Update: We need to rethink what is possible. For me, the Little Wild Horse was quite doable on my CX bike, especially if I could run 40s or bigger. I was just as fast on my hardtail MTB, and had a lot more fun. The big loop on CX? Way out of my league.
But results don't lie. The past two years the men's winner has been on a CX bike, and many in the top-5 men were on CX last year. We have seen women finish top-5 on CX bikes, too, but not yet win it.
But don't be fooled. It takes most riders well over five hours to finish, with zero pavement. You will take a pounding on a CX bike.
As always, it comes down to tires, your ability to handle almost constant vibration and your comfort level going fast through rocks.
Here is what we have posted for the past few years: Going the full distance? Use a mountain bike.
The real question should be "which tires?"
Bike selection will certainly be something deserving of some thought, but a MTB is really the best way to go. Comfort over several hours is paramount. The entire route is unpaved.
In some sections a CX bike goes like a rocket on the hardpacked dirt. There are two descents where disc brakes and the cush of full suspension are welcomed. I have ridden the Little Wild Horse on a carbon CX bike, 700c x 33 tires, 48/38 rings and 11-36 cassette. Did it, but wished I had more tire on the descent. And I only rode 31 miles that day.
If you do not have at least 35c tires, you will very likely have a hard time keeping air in your tires. There are fast road sections where you will easily top 25 mph but they also have large rocks lurking. Hit one at that speed with a CX race tire and it will fail. No fun.
You might be surprised how much tire you can fit in the front of a CX race fork. I can easily fit a Kenda Slant Six 29 x 1.8 in the front. I have run it at 30-35 psi for laps on the Little Wild Horse. Big improvement!
Most comfortable has been a dual suspension MTB, but it was slower on some of the fast roads. Trade-offs, of course.
For sure you will want Stan's NoTubes sealant in your tires and very good lube on your chain. There are spiky things out there, and the dust is hard on the chain. Don't skip either of those two. Each aid station will have additional lube, Stan's NoTubes sealant and limited tools and a pump for all to use.