I'm a little aggressive but very nice. My last set they took off about 50 per tire, including the certs. I bought 8 tires too, though. I think the key is to talk to the manager and talk to him over a period of two days or more. Soak up his time, make him invest in you. When you are done he will feel like he will have wasted a lot of time if he doesn't get close to what you want and also he will know you are serious. They want to sell tires. I also do this two or three shops....make them compete. I've been a customer of discount for at least ten years. I won't buy tires anywhere else. They always treat me right. I've used certs as well, no problems.