275/40-R20 Mickey Thompson ET Street S/S: what PSI at the track?

Start at 22 and work your way down .5 psi at a time until the traction feels right. Dont go below 14 iirc. You can write to MT and theyll tell you for sure. I found my ET Sreet Rs 305/45/17 likes 16-17 psi here in So FL.
Don't expect alot of strip performance out of 20" rims tho.