Making the Great Divide Mountain Bike Route Even Greater: Rollins Pass/Argentine Pass

Like this? Follow me:

The GDMBR in yellow; alternative in red

The Great Divide Mountain Bike Route is without a doubt one of the preeminent off road touring routes in the US/Canada. Now that I’ve ridden the route essentially twice and have done some extensive touring within Colorado, I can’t help but think how one could enhance it.

Personally, I enjoyed my time more when the route stuck close to the actual Continental Divide, rather than opting to drop down into a relatively easy going valley or basin to gain some mileage towards the end goal (finishing!). I always greatly anticipated gaining the summit of the passes, then rocketing down. Knowing Colorado a little more intimately now, it’s a shame how much of Colorado is missed with the relatively easy path the GDMBR takes.

The GDMBR has many goals, and one of the most important one is to get a heavily laden bicycle and rider (cyclists on a mountain bike, pulling a trailer) eventually to the end of the route. If the route is too long, too hard, and/or with too many Divide crossings, it’s just never going to realistically happen for a good majority of people. If we throw these constraints out of the window, and focus on the goal of staying as close to the Divide as possible, while also keeping the route terrain somewhat similar: gravel roads to 4×4 trails, we start drawing out something a little different.

Below, I’ll be describing a route that takes you off the official GDMBR just before Ute Pass, and rather takes you up and over the Continental Divide at Rollins Pass, parallels the James Peak Wilderness as you travel south to Idaho Springs, then brings you back west to go up and over the Continental Divide again at Argentine Pass, finally depositing you once again onto the official GDMBR in summit county. It circuitous and it’s a whole lot of fun .

At 11,660‘ for Rollins Pass, and a whopping 13,207′ for Argentine Pass,  these two added Divide crossings rival the highest passes on the GDMBR, and add much punch to the route. I do not suggest this route for cyclists pulling a trailer – going over Argentine Pass will not be pleasant (ask me how I know…) but for the modern bikepacker with lightweight, saddle and framebags, this route will be awesome.

Note though: you will be trading an easy 33 miles of mostly paved highway and bike path riding that includes a total of 1,757′ of climbing, mostly over one pass (Ute Pass) which crests at only 9,600′, for a monster 120 miles of mostly rough, gravel/4×4 tracks (and a little frontage road riding between Idaho Springs and Georgetown) including 14,500′ of climbing up those two Divide Crossings.What will take you a few hours to get Summit County will now take you a few days.

If you like hiking or unloaded mountain biking side trips, then yeah: this route is made for you. Both Winter Park and Nederland have copious trail systems to explore; you pass right by the quiet Byers Peak Wilderness, right by access to the James Peak Wilderness/James Peak, and you can easily access not one, but two 14ers (Grays and Torreys) from the vicinity of Argentine Pass.

What you’ll skip out on riding is: a paved road that goes through the industrialized Henderson Mining Operation, and some highway riding.

Note: Mileage and Directions will be approximate, use the GPX track for the best navigation!

Start at Co Rd 3, south of Ute Pass HERE
Turn Left on Co Rd 32
Co Rd 32 is a well-maintained gravel road with a bit of traffic at peak times. This road is much like a lot of the sections of the GDMBR, so it makes a good introduction.

Side Trip: Before Mile , you’ll pass County Hwy 325. Turn Right on County Hwy to access the Byers Peak Wilderness. Free dispersed camping is available, as well as a variety of hiking trails.

8.5 Continue East on CO Rd 50 towards Fraser
18.5 Right on Co Rd 5 to US 40

Side Trip: Fraser is a good place to resupply before Rollins Pass, as there’s a large grocery store in town, as well as many bike shops. The MTB Trail System in Fraser and Winter Park is extensive!

Continue on US-40 South for a few miles – there may be access to the Fraser River Trail (paved bike path) if you would like to skip some highway riding.
23.9 Left onto Corona Pass, and get ready to climb up to Rollins Pass! The road will start as a wide, gravel road, and will slowly become less maintained and narrower. The grade will be very similar to other railroad grade passes on the GDMBR.
37.4 Reach the parking lot for Rollins Pass!

Head east either on CoRd 501, or the road slightly north of it, which may/may not be passable, depending on snow conditions. There’s opportunities to ride over some railroad trestles, which is very cool. Eventually, you will get to an area just north of the Needles Eye tunnel. Find a small path that goes over the tunnel just to the west, which will rejoin the actual old railroad, at the other side of the tunnel. Once back on the track, enjoy the 13 miles of downhill to the East Portal Road! The conditions of the route on this side of the pass will be more more rough and rockier.

Needles Eye Tunnel, Rollins Pass

Rollins Pass, East Side

52.2 Left on East Portal Road
54.4 Right on Mammoth Gulch Road

Side Trip/Resupply: There is a tiny store in Rollinsville ~ 5.5 miles away by continuing straight on East Portal Road; Nederland has a grocery stories and full services 10 miles away – once you reach Rollinsville, turn Left on Highway 119. There’s a MTB trail system local to Nederland, if you’d like to take a day to sample the local trails.

57.9 Continue on Mammoth Gulch Road

Side Trip: James Peak Wilderness! Instead of Continuing on Mammoth Gulch Road, take a right onto the 4×4 track west.  Dispersed camping sites along he road are available. In the morning, hike up James Peak. The trail is not technical, and James Peak is right on the Divide itself.

60.2  Right on Apex Road
65.8 Right
on Bald Mountain Rd/King Flats Rd
Along this road, you’ll pass some private property, and some scary signs. Don’ take any of the private roads and consult the map/gpx track.
Take a left off of Bald Mountain Road, towards Russel Gulch Road. Pass to your left Nevadaville Road, and Roy Smith Road. Your road will turn into a 4×4 track and go over the west shoulder of Alps Hill. The 4×4 section isn’t too long, and you’ll end up on the other side, still on Russel Gulch Road. Take the road east until you run into Virginia Canyon Road.
69.5 Right on Virginia Canyon Road
This road will take you on a wandering, switchback route, passing many old mines and mills, eventually leading you into the heart of Idaho Springs. Don’t forget to look south towards the towering Mt. Evans! You made it! Resupply is bountiful in Idaho Springs, all services are available.
75.8 Right on Placer Street
This is the start of the established I-70 Corridor bike route, which stays on the side roads next to I-70. We’ll be taking this only till Georgetown, but you could theoretically take this all the way to Glenwood Springs, if you’d like. Follow the signs for the bike route. Once near Georgetown,
87.4 Pass by Georgetown Lake
Georgetown is the last town before Summit County, so stock up if you haven’t already, we still have one Divide crossing to do!
88.7 Left on 6th Street

Bailout Point: If you would rather not go over Argentine Pass, you can instead take a right on 6th Street and continue your way on the Frontage Road bike route, up and over Loveland Pass, and meet up again with the official GDMBR in Frisco.

Side Trip: Grays and Torreys! If you would like to hike the pair of Colorado 14ers, Grays and Torreys, here’s your first (of three!) chances: take a right on 6th Street, and continue your way on the Frontage Road bike route, until the winter trailhead for Grays Peak (Stevens Gulch Road), near exit 221/Bakerville (no services). After this trailhead, the I-70 Corridor Bike Route turns into a paved bike path. Instead of taking the path, head left up Stevens Gulch Road for 3 miles, to the summer trailhead. Follow the hiking beta for Grays Peak, East Slopes.

88.8 Right on Rose Street
89.0 Left on 2nd Street, and you’ll start climbing the well-maintained Guanella Pass Road. After a couple of switchbacks, you’ll exit this road and get back onto dirt at,
91.5 Right on Leavensworth Creek Road, and another set of switchbacks
97.6  Leavensworth Creek Road switchbacks sharply right, after going straight for a few miles. Instead, go slightly right and follow a more primitive road, up to the summit of Argentine Pass! Prepare for quite the climb.
100 Argentine Pass!

Side Trip: If the day is young and the weather looks good, leave the bike, and travel North on the ridgeline to Mt. Edwards, a Colorado Centennial. Once on Edwards, you can then take the Class 2+ ridgeline East to the summit of Grays Peak. Mind the weather.

The backside of Argentine Pass will be in worse shape then what you’ve come up, and in one section, may have feature a small gap that will need to be dismounted. The bottom portion is in much better shape. Singletrack!

102 Left on FS 260 on the valley bottom

Side Trip: Grays and Torreys! This is your third chance to bag these 14ers. Use the hiking beta for the South Ridge route to Grays Peak.

Continue on FS 260, which will turn into CoRd 260.
107 Right on Montezuma Road
111.6 Left on US 6
114.9 Left on Swan Mountain Road
119.8 Cross Highway 9, and onto the Swan Mountain Rec. Path. Take this path west, until it leads into the Summit County Rec Path.
Left on Summit County Rec. Path and back onto the official GDMBR!

Where to go, from here?

One can easily get back onto the GDMBR, and continue South, never to sway from the main track again.


If you’ve been bitten, Colorado has a lot to offer, and it’s going to pass you right by, if you take the GDMBR. Sure, Boreas Pass into Como is fun, but going through South Park is boring and windy. If you want a step up from wide gravel roads, consider taking another detour away off of the GDMBR, and take the Colorado Trail as it crosses over Highway 9 as it goes up and over the Tenmile Range. Continue on the Colorado Trail until Marshall Pass, where again you will cross paths with the GDMBR. High country single track adventures await you – plan on taking a few more days/weeks more than the direct route. To stick even closer to the Continental Divide, including riding the Divide itself for many miles, one could travel even farther on the Colorado Trail, but then, there’s no easy easy way after Marshall Pass to rejoin the GDMBR.

Whatever you decide to do, I wish you luck!


Support Justin on Patreon!
Become a patron at Patreon!
1 Comment
Newest Most Voted
Inline Feedbacks
View all comments
6 years ago

[…] on how much fun this route is, and also some great alternative lines to the official route. My last foray into this topic lead to a major reroute up and over Rollins Pass to the east side of t…. That alt. adds major miles, and a whole lot of adventure – it’s pretty […]