Hamilton jumped the Aston Martins of Lance Stroll and Fernando Alonso at the start to briefly run third, but thereafter he slid down the order, complaining at one point that even with his DRS open he couldn't challenge the car ahead.
Hamilton eventually finished eighth, while his team-mate George Russell fared even worse and retired with a cooling issue.
"My guess is that the floor is not working," he said when asked by Autosport about his DRS radio comment.
"The floor is not sucking it down. So that pushed us to go to a higher wing, and then we're just massively draggy on the straights.
"And we're losing so much time on the straights, there's nothing I can do about it, and then we're just sliding through the corners. So we have to look into why that is the case on this rough circuit."
Summing up his afternoon, he said: "Just the tyres are overheating, slow on the straights, no grip in the corners."
Hamilton said even passing the two Aston Martins at the start hadn't given him much cause for optimism.
"No, I knew that we'd have a difficult day," he said. "Nothing changed in the car from yesterday to today. So I knew it'd be a tough one.
"Yesterday I just ate through the tyres with an unexpected lack of pace. And then I think I drove better today in terms of making my stints, but we were just slow."
He added: "I don't know. I'm sure there's something within the set-up that we might have been able to have done a bit better, but whether or not that would have put us further up, I can't say."
To add to his woes, at one point Hamilton reported that it felt like his left front wheel was turning right.
"Yeah, it's super strange," he said. "I wondered if the tyre maybe hadn't been done up or something, but the car started turning right whilst I was going left. But it was fine in the end. I think it must have been just a gust of wind."
Hamilton didn't know if the Interlagos issues were track-specific or a more general setback.
"Hard to say," he noted. "Ultimately, in the moment it is a setback, but as a team, we'll just come together, and we'll try and push forward.
"There'll be a lot of analysis this week after today and I'm sure there'll be things we were like 'Ah maybe if we've done this it, would have been better,' but I think still ultimately the car didn't work here for some reason, and that is the way it is."
