I think I answered you on our Arinsal forum but you'll go past 3 supermarkets which normally all sell chains once you've come across the border into Andorra, or you can stop in Andorra la Vella. The roads are kept pretty clear unless it is snowing particularly heavily.
Steve
driving from Barcelona to Arinsal
bob uk
Driving from barcelona to arinsal for a short ski break, mid -Jan. Not sure that the hire car company offer snow chains.
Just wonderered ,if there was a good place to hire/ buy them, near the Spain/Andorra border.
Drove from carcassone to font romeu, last year, sans chaine, in a snowstorm and never again.
I would prefer to have some, even if its only for 'peace of mind'.
Finally, are the roads up to Arinsal, usually kept open and what historically is the weather like mid-Jan. (I have drove up to font romeu, loads of times, in jan/ feb, with little problem, but never to arinsal)>