You will have to pick up your bag in SP, go through customs/immigration and then re-check your bag to Rio. I wouldn't mess around with time either- last time I stopped in SP I ended up missing my flight because immigration took an hour and then I waited over 30 mins to re-check my bag and by then the flight was closed. That was last feb when some brasilians were actually still traveling though so airports were more crowded. Just be cognizant of this, especially if you arrive late.