Puelo to Puelche Although not part of the Carretera we came down this way and this section had river cobble gravel and numerous really steep hills trying to get around the coastal mountains.
Puelche to Hornopiren This is the start of the Carretera gravel and there is lots of traffic, big trucks and buses, dust and lemon to potato sized road material. There are relatively few hills if that is any consolation (or much scenery). It was a real let down for us thinking we had over a thousand kilometers of this type of road ahead. Thankfully this was some of the worst. The scenery starts getting really good again from the ferry ride at Hornopiren to the south.
Queulat Pass The north side of this pass is very steep with lots of switchbacks. Because it is so steep the road is all churned up with loose gravel and powderized dirt. Once your on top of the pass the road is fine and the scenery is some of the best. Many bike tourists going north to south talked about this climb as the worst memory they had when the conversation turned to bad roads or difficult climbs. The pavement starts at the junction to Puerto Cisnes on the south side of the pass.
West of Villa Cerro Castillo About the first ten kilometers out of Villa Cerro Castillo is hilly with bad gravel and will likely have a big head wind. Once you get back to the valley floor the ridding is fine in fact the dirt from there to Puerto Rio Tranquilo is some of the smoothest. Hopefully they will not decide to improve it and add large river cobble gravel.
El Chalten North The first ten kilometers or so north of El Chalten is not steep but the gravel is some of the worst. There will likely be strong winds from the ice fields on to the plains. The scenery here is also some of the best so you will be trying to decide weather to cry because of the roads or have tears of joy with the stunning scenery. In a car you wouldn't even notice the road or the wind most likely - well maybe the wind.This is the wind that Patagonia is famous for. On the road out of El Chalten you will feel like superman if you are headed east with a big tail wind on the perfectly smooth paved road.
Trevelin to Futaleufu This is not part of the Carretera but many bike tourists use this route to skip the northern part of the Carretera and all the ferries. They choose to tour on the Argentinian side because it is paved and also has good scenery. The climbing isnt bad it is just the same bad type of large uncrushed river cobble as the bad sections listed above.
San Martin de los Andes to Hua Hum Also not part of the Carretera Austral but also frequently part of bike tours. More bad gravel on the way over to the Chilean border plus the scenery is not very good until you get to the pass. This section is frequently written up as a great tour over to Panguipulli. Much of the Chilean side is paved but unless it is early in the year when there is a lot of snow on Volcan Choshuenco it is not near as scenic as much of the Carretera is.
General comments If you are coming from the much of the US you would not be expecting such poor quality gravel on a major gravel road like the Carretera Austral. Most major gravel roads in the US are made with crushed gravel where the largest stone is typically not much more than an inch around. They apparently do not have the budget for that in Chile and Argentina unless it is a base for a paved road. They just scoop out gravel from river beds and spread it around. The biggest problem in the US with a crushed gravel road is that if it is not bladed then you get a washboard surface. Well they have washboard gravel roads here too but if they blade it and it has big river cobbles in it, it is not that much better maybe even worse for a bicycle.
The gravel road experience would be a lot more tolerable with wide low pressure tires like mountain bike tires. Like I mentioned in the gear section if I had to do it again I would go with two sets of folding tires, one for pavement and one for gravel. A front shock would have helped a lot too if you can figure out how to do the loads so you do not need to carry much up front.
