Hi JP,
All good advice above and if I may add to it.....bear with me....
Quick background if you don't know me. Born in Asturias, never missed a summer in 53 years, educated UK, live in Valencia. Every year I migrate my bike north to Asturias where we have a family home in order to have the bike there during the holidays, and then finish up with a group from UK riding around NW Spain in September, after which I ride back home again.
I'm a planner but not in the OCD way, I just enjoy thinking about my trips. First to admit that I don't know all there is to know about northern Spain but having ridden most roads there (it ain't exactly big) I do have some experience but I'm still very much learning myself. I'm starting to think about my trip in May also.
I am going to
try and keep this simple. If you want a full on version, PM me but be prepared for a detailed document. Wapping will doubtless berate me for not sharing but it's not that, It's just that the post will be too long and of little interest to the majority.
First, don't over-plan this and don't set yourself an
itinerary First and last stop is a great idea to pre-book. Leave the rest on the fly.
Second, have a Plan A & a Plan B. Be prepared to ride south of the Picos if the wx is going to be shite because it can rain for weeks on end there. There are some great roads and places to visit south of the Picos and the wx is much more stable.
Avoid motorways unless by-passing major cities. Always take the N or tertiary roads, they are virtually unused because everyone takes the motorways. They are the best roads and well maintained mostly. Coastal route the
N632/634 is your friend stay on it all the way to Ribadeo.
If the weather is shite, i.e raining moderately with thick low cloud, avoid the passes and the interior roads. Rain and fog do not make for a good day's ride.
Places to visit stay (Coastal) all along the
N632/634
San Vicente De La Barquera,
Lastres,
Cudillero,
Cabo Busto Lighthouse,
Luarca,
Puerto de Vega,
Viavelez,
Tapia De Casariego,
Ribadeo.
Interior (plus roads),
Potes, N621
Cangas de Onis, AS114 (western approach) or N625 (southern approach) Link the N621 & N625 with the LE2703/2711 for two great mountain passes but avoiding Riaño.
Tarna Pass, AS117
Somiedo, AS227
Cangas del Narcea (various routes, all good)
Pola De Allande with the Palo Pass. Pola has a great restaurant called La Allandesa. Arrive hungry, portions are enormous!
South route.
Riaño,
Puebla de Sanabria (Beautiful) via La Bañeza.
Parador de Santo Estevo near Ourense.
Chaves (Bragança) Stay at the Forte de Sao Francisco. Look it up, biker friendly, safe, wonderful in every way and where we have booked already for September.
Accommodation.
With the exception of the first, the last and the Forte DSF (if you are going that far south), do not need to be booked. It will tie you down. One double room for 2 people will not be a problem to book on the fly (except FDSF, as I say).
If you were to head along the coast, then south to Bragança or just Galicia in general then without a shadow of a doubt go via Navia - AS12 - Boal - AS28 - Fonsagrada and make your way south to the Sil Canyon where you will find a Parador (Sto Estevo) which was a 10th century monastery. Not cheap but very beautiful.
A word of caution.
Your biggest dangers at that time of year are the shaded, damp bends which can become mossy. Not often of N roads but the AS ones can be a bit like that. Early morning, when the sun is in your eyes, you might have trouble.
Enjoy.