I'm beat. I drove up to Gallup, NM yesterday to pre-ride the race course for the upcoming Dawn 'til Dusk 12 Hour race. The course was a blast - even with the few leg burners that are in it.
According to the guys at the Scoreboard (505-722-6077, no website), the trail is pretty new. At last year's race, they had just finished it so the racers were basically burning it in. There's not many mountain bikers in Gallup, so the trail doesn't see a lot of traffic. While most of it was pretty well burned in, there were sections that still had that new trail bumpy feeling to it. A squishy will definitely save your back if you're riding solo or duo.
The course starts off with a climb, nothing crazy but it lets you know that's its there. As you finish up the first mile, you drop into this really fun slick-rock section that flows great. It's just buttering you up for the worse part of the course. According to my Forerunner, there's a 25% climb on the course right after the slick-rock. You go from flowy, full toothed grin to a nice halt as you grind out the climb. It's only a couple of hundred yards, but both times I did the course my heart rate spiked and I felt like passing out would be a blessing - wouldn't have to keep riding. I can't imagine how that climb would feel at hour 10. Of course, by then I'd be little ringing it instead of middle ring, so that'd probably help.
After that "treat", you have a little more climbing before you're onto what I consider the start of the second mesa. The trail gets into this groovy flow where you're big-ringing it and it feel like you're hauling. My max speed was only 18.6 mph, but it felt like I was doing 25 through parts of it. There's a couple of corners through this section that are sandy. I figure as the race wears on, these are going to get messy. Something to think about. If you're not 100% confident handling skinnies, you might want to consider a 2.1+ for some extra traction through those corners.
The end of this flowy section, about 3.5 miles into the course, you have a really abrupt change. It goes from super fast into a quick 90 degree turn and climb through some rocks. Nothing technical, but if you're not expecting it, you'll be in the wrong gear for that climb. After this, the trail calms down. There's still some fast sections - all of it's middle ring with some big ring sections. You go through a really cool bunch of rocks a mile or so from the turn around point - lots of sand through this section though, another spot that'll bog down once the race gets going.
Once you make it to the turn around, you fly with a bunch of up and down with a really good flow. A strong rider will be in the big ring most of this section, and a 29'er would fly. About a mile from the turn around you go through a nearly 180 degree turn 10' from the edge of one of the mesas. My first trip around I checked the edge - 50' straight down. An awesome view, but you probably won't be paying too much attention to it during the race. From the turn around you go along the edge of the mesa for few hundred yards, then drop down off of it. There's a few sections with blind corners that feel weird the first time you do them, but once you know what's coming you can bomb through this section. That said, there's a few places you want to make sure you make the corner. In one corner there's a nice big rock waiting to impale you and another has an old tree that looks like it would love to grab you.
You'll cross back over into the 3rd mesa - or the expert loop - and you're greated by a crazy descent. No drops or anything DH-oriented like that, but on an XC bike with a super aggressive position it felt like I was out over the top of the wheel on a few sections. Again, the first time through it was the worse, the second time I was sliding through the corners like a wannabe pro. From there, you have a little more climbing back up to the last cross over where you start the final descent back into the starting line. At the last cross over, you have four miles to go. At this point, you're coming off of the highest point of the course.
The descent starts off fun and fast enough, then you drop through a crack and before you know it, you're at a turn that if you miss you've got a 10' drop onto the next rock face. This characterizes the rest of the course. There's nothing technical about it, but some of the exposures make a simple switchback feel like you're on a 2x4 skinny. There's a couple of places where you're looking at trail that's 100' vertically below you, and you get there in a few hundred yards with a couple of switchbacks. Again, it's nothing crazy steep, but you would do good to preride this section at least once before the race.
I ended up doing two laps - one Saturday afternoon and again Sunday morning. The Saturday one included several breaks that were the result of not knowing when to push on the course and the 4 hour drive up. Both laps had ride times sub 1:30. Today's lap I felt like I was keeping a pace that I could have kept for several laps in a row. Once you get the feel of the course, you should be able to fly around it.
Again, I'd recommend a dual-suspension for the course if you're doing duo or solo unless you're just into pain. The course is still raw in some areas, so a hardtail or rigid will really beat you up. Of course, if that's what you're used to.
Last year's winner put in 9 laps with the second place rider putting in eight on a SS. Personally, I would think a SS would really suck on this course. I was constantly switching from my big ring to my middle ring for descending or climbing respectively. With a SS I think you'd end up with a gear for the climbing or a gear for the descending. Of course, an XC race isn't won going down the hill.
Last year's race also was "almost spitting snow" with a crazy wind. I was told to expect the wind again this year, but we should be a no-go on the snow. According to the local bike shop, they should have snow on the ground right now. Thankfully, though it was cold - 28 degrees when I started at 9 - there was no snow to be found.
As for the 29'er verses 26": I'm may take both, but I'm leaning toward the 26". I think the second mesa - the middle of the course - is perfectly suited to a 29'er. Those first few climbs, though they're not long, do get steep and would suck the wind out of you. And on the final few miles there's a few switchbacks that would be pretty tight on a long wheelbased 29'er.
As for pre-riding, as with any race course I would definitely recommend it. If you can't make it to Gallup to pre-ride before the race, I would try to make it in early enough on Friday afternoon that you at least do the climb up to the first cross-over, and instead of going straight, hang a right and come down the final descent. That's about a 6 mile loop that'll show you the worse climb and the worse descent. Depending on how strong you're climbing, plan on 30 - 45 minutes for that part of the course.
And finally, here's a profile of the course as my GPS rendered it: