Originally Posted by
noglider
I recently rode on NYC streets on 32mm tires with 30 psi. I didn't bottom out, though it was pretty risky. I'd say you can go well below 30 psi on your new tires without risk.
IMO 30psi in a 32mm tire on NYC's potholes streets is pushing the limit. Probably fine until a pothole suddenly appears out from under a cab at 20 mph or more. Plus, it's going to cause more drag than necessary.
Optimal tire width and pressure is about balancing, ride, rolling resistance, rim protection, handling and traction. With that many variables, no simple formula is going to get anyone closer than to the right ballpark. Afer that it's about riding and making judgement calls based on priorities.
For some perspective. BITD whe we were riding 3-speeds with 26" tires (35mm or so wide) we rode at roughly 35psi, until better tires were introduced which made 50psi possible. IME, once we tried 50psi, we never looked back.