315 or 325 tires on early a?

Well I know it took me a while but I made it out to the track today and made my first runs on my 295/55/15 M/T drag radials. I ran them with 18psi after talking to several different people. First pass ran 11.59 and noticed a little slipping. Second pass ran another 11.59 with same slippage. Now it was 95 today and started thinking my car usually runs 11.5 but maybe with the heat and crappy track conditions this is what it was going to run today. So once running the two time trials I dial my first race in at 11.54. I did a longer burnout this time and the car ran 11.549. Second race dialed 11.53 and did longer burnout again. Car ran 11.49 and that sent me home. That launch the car really hooked good with no tire spinning. So you asked if they worked and the answer is yes I was able to get them to work and achieve my normal time the car runs. Jayson