As I mentioned, I started at 26 psi checking the contact area by putting a strip of white shoe polish across the entire thread width then driving a short distance to see where it wore off first. At 26 it definitely wore off in the middle of the tire first, indicating the pressure was high. I lowered it by 1 psi increments and kept repeating. Finally at 20 psi cold it had even wear and contact across the entire width. Allowing for thermal expansion, I agree with turbobuick, 18-19 psi cold should give the optimal contact patch and best grip.