Some of us larger folks also gave up on 23mm tires long ago. I weigh 240, and I haven't used anything smaller than 32mm in years. I'm no slower and a lot more comfortable than I was on 25s. Most of my everyday riding is on 37mm Paselas at <80psi. FWIW, my 12-mile commute takes within seconds of the same time no matter what tires I use.