My Scion TC 2005 pull to the right. Help!?

Recently bought a Scion TC 2005 has 57 000 miles on it, got 4 brand new tires, did alignment twice, + balance, picked the best two rims and put them in front.Does n seem to be the caliper holding. When bumps on the road or is very uneven its really bad. Any body can help i will really appreciate it.