Well... I am not a tyre engineer but... What are considered tintop tyres have, for instance, similar load ratings to the more specialised tyres. I am assuming that load ratings relate to the weight of the cars. On 185/60R13, 80 load rating is the same for Toyo R888R and on most, if not all tintop tyres of the same size... Which begs the question... Why are specialised tyres done with such high load ratings, even Caterham ZZR/ZZS are 83 load index rating... If they were going to be done for lighter cars, then ratings below 80 would be more than adequate...
Sorry I am being too pedantic.
I have to agree with Eugene. Tread and compound are more important.
I have driven to the Alps from Portugal and back, on Nankang XR-611 and survived. Maybe I am a bit of a
Bloody hell! Buy anything legal and drive it... adjust driving style to tyres and visit the Douro Valley