tire pressure

I've been running 13lbs for 3 years now.
Friday night TNT I tried from 15 to 17 lbs in my 29.0x12.0x15 Hoosier slicks on stock leaf springs, caltracs & Calvert 9 way shocks.
I found the best 60' was at 16lbs. so I thought I was ready for racing Saturday.
Saturday it never hooked and I only lasted 2 rounds due to lousy tree and 60' with lots of spinning.
I need to check spring eye and shackles for possible binding, but I think it just needs to be adjusted correctly.