Geoff, we’ve done the 285S route out of Denver a number of times pulling our Lance 2285 with our LC. In fact, that has always been my preferred way to get into the mountains as we love the Buena Vista area. There is a fair bit of up and down on that route. Here are a couple of tips:
- As we go through a few miles around the community of Conifer the segmented cement roadway causes a lot of bouncing/porpoising for us. (The bouncing happens to a slight degree when I’m simply driving the LC through that area so it has a lot to do with the wheel base of the LC and the length of the cement segments.). But it does end eventually.
- There is a section past Pine Junction where there is a significant descent and the road goes from 2 lanes to 1 and around a curve. The speeds in that section go down to 45 for a reason. (Bad accident there a couple years ago.). But it is short.
- The steepest section is what is called Crow Hill. It descends into the community of Bailey. I think it is 8%. There are warnings signs for trucks. I use 1st and 2nd to keep the speed under control without needing to ride the brakes. Someone may not like you going so slow but it is only a minute or so and when you get into Bailey the road becomes 2 lane going through town.
- Then there is Kenosha Pass but it is not a problem. Passing lane for the first part of the climb. I have no problem maintaining the 45MPH speed going up.
- There are a couple lesser passes but not a problem if you are not pushing the speed. A long running and gradual descent into Buena Vista (lovely area with some great, easy off reading) with lots of curves.
- Now, the big question on this route is what is called the Weston Pass fire near Fairplay. It was bad enough on July 4th weekend that they had closed the highway. But that was a couple weeks ago.
- The other consideration with this route is that you still need to go over Monarch Pass. I’ll discuss that below.
Now if you want the flattest route it is probably the one you found on Google. Take I25 south just pass Colorado Springs in order to pick up US-50. BUT, don’t go all the way to Pueblo. There is a cutoff often used by trucks that takes you from I-25 to Canon City. If you go this route and can’t find that cutoff let me know and I’ll show you where it is. I think Google used that on the route it gave us last year when we towed the trailer to Ouray from Denver.
- This route (I25, US-50 to Montrose then south to Ridgway then over Dallas Divide) only has one big pass to go over. Plenty of ups and downs but very manageable. This route is our preferred route to get to the San Juan mountains with the trailer.
- The drive along the Arkansas River (from Canon City to Salina) is lovely.
- Monarch Pass is the bear. 12,000’. Lots of curves. Some with little shoulder. 6-7% for about 9-10 miles on each side. I think I used 1st and 2nd gear (on my 8-speed) to manage speed going down. I kept it about 20mph primarily because of the tight curves and I didn’t want to have the speed build up and then have to break hard for a curve. But it doesn’t last forever. And when that pass is done, you are good to go.
- @Ohnoitsbreaux, is right about Gunnison. We actually stayed at a small RV park just west of the town for a few days last September. The Crested Butte area is awesome but you probably won’t have time.
- @Ohnoitsbreaux is also spot on about the Dallas Divide out of Ridgway. There are a couple of country roads that run from the highway south to the San Juans and Mt Sneffels that go through the Ralph Lauren ranch. I’ve done a bunch of photography in there but you won’t want to drag your trailer along that road. And Last Dollar Rd is likely to be one of the easy trails runs for the weekend (if they do easy runs) and an awesome drive (be sure to do it going north to south starting at the Dallas Divide as that offers the best views) but you won’t want to take your trailer on that!
- BTW, there is a toll beltway around the east of Denver. I don’t know that I would want to go through Denver during rush hour. Toll road isn’t cheap but it has far less traffic.
The I70 to Grand Junction route is a toss up when towing a sizable trailer. I’m don’t enjoy towing the trailer up and over the “Triple Bypass”. Floyd Hill, Loveland Pass (Eisenhower Tunnel) and Vail Pass. Just too much work and we see lots of mountains anyway. We towed the trailer over Eisenhower Tunnel a couple weeks ago. It was fine, just not something I would choose to do. But we were headed to Steamboat Springs and no other route made sense. I haven’t yet done Vail Pass. I find that one a bit more imposing Han Eisenhower Tunnel due to the condition of the tarmac in some areas. I haven’t done Fremont Pass from Copper Mountain over to Leadville (suggested by
@Ohnoitsbreaux) with the trailer. I have done it a few times on a bicycle and it is one of our favorite passes. About a 7% grade doing up. Very steep but very short curving descent just over the top. Then a gradual descent for a few miles before a short, each climb to Leadville. After that it is an easy drive south through Buena Vista towards Poncha Springs and US-50. But then you need to go over Monarch Pass. That’s 3 big passes.
If you take I70 over to Grand Junction it certainly is a lovely drive. And once you are over Vail Pass there are no more big passes. Grand Junction to Ridgway though Montrose is easy. This is why we plan to store our trailer in Grand Junction (when it is not in Oregon.).
Let me know if you have any more questions. The one section I haven’t done with the trailer in tow is the Dallas Divide from Ridgway over to Telluride.
one last note— Last time we all did Ouray (two years ago, same gathering) we had a guy with 100% stock...including street tires and running boards. He bent his boards, but was otherwise fine including black bear and other trails that tend to be described as more difficult that they really are. 
