I run 42 as I tow all the time (everyday) and I have gone through more tyres over the years than I care to think about.... before people start going on about towing there caravans and get big miles out of there tyres I tow around town and make many turns in a day.

Towing heavy trailer in the suburbs just kills tyres...... I have tried all different ways and know how to get the best out of my tyres, I have even under very heavy load run 46 in the rear for single trips.

I would never run anything less than 38 for normal road use but find the sweet spot is 40.