Rank prediction is only a rough calculation of your rank based on their own assumption of the paper difficulty,so don't believe any rank prediction 100%.
FIITJEE's rank prediction is doing good for the past 5 years.They predict worser ranks for you so that you will be glad when you see the actual IIT-JEE result.But FIITJEE has predicted upto 15000 ranks this year which is a huge increase than last year.If your rank falls within 10000 in FIITJEE prediction(which i hope would) believe it(its worth believing). Otherwise you may not get a rank or a seat as IITs may not increase the seats that much.
FIITJEE solutions are correct except for Q11 in their paper1 (Br2/NaOH reaction) for which the answer is A,B and not A,B,C.
The prediction by resonance is worst of all.They give AIR(OBC)1 to all OBC candidates and far superior ranks to GENERAL candidates, so don't believe it.
I think career point also predicts the rank good giving a shorter range than FIITJEE.
Time and Askiitians also predict the ranks good giving a shorter range so that it gets more precise.
The following links may help you:
Wish you all suceess in IITJEE..:)
Vasanth Kumar Balakrishnan...................:)