Hola
@OCHAR .
Whilst google translation is reasonably accurate the major stumbling block is that the length of the folded/packed bike (including its box or carry case ) must not exceed 1200 mm (about 4 feet for those who think that way). What train can you take your bike? :
1 AVE - NO';
2. Media Distance - yes if it meets the packed dimensions conditions. (Very occasionally there is a cargo compartment on these trains which will allow for bikes to be carried - I think it might be the overnight train from Santiago to Madrid);
3. Local commuter trains - yes. Both complete and packed (often depends upon passenger numbers).
Back in 2015 I took my bike (in its box - just over 1500 mm) from Madrid to Pamplona - luck for me the conductor realised I was a pilgrim and just ignored that I had it taking up 4 seats. (Also the train was only half full). To get the bike back to Madrid I ended up going to Velocipedo cycle shop in Santiago - Rua San Pedro 23 (tel 981 580 260) they are actually right on the camino trail (
Camino Frances) as you come into the city following the yellow arrows. The will pack your bikes and arrange transport back to Madrid (but it will have to go to a hotel/hostel/home - somewhere where someone is actually expecting the package. You cannot send it directly to the airport). I think it cost me Euro 50 or 65, but it was well worth it. Good luck.