I am in canada. The proper winter and countless annual freeze/thaw cycles makes for crap roads. The good stuff never lasts long. Cracks, patches on patches, etc. I will go higher pressure for select routes and goals (hillclimb up a smooth road).
Yeah, for reference, with that combo and a 20lbs tt bike i would start you at 81/75psi!!!
If your roads are good, i think 110psi or a bit less would be near spot on for your weight.
Here is the silca post (or one of them... he has a series of 5 articles on tires). https://blog.silca.cc/part-4b-rolling-r ... -impedance
Here is the data that has influenced pressure choices back out of the stratosphere for most of our typical “crappy roads”. (Some) pros have known this stuff for some time, but it seems to be in the general public only in the last 3-4 years. A great way to sell high end bike pumps (i have one, and love it). The real inspiration was mastering cobbles at pro speeds, but it was a surprising finding in how much things like fresh pavement or chipseal benefitted from lower pressures.
Another key here is that hitting “perfect” pressure is impossible. But there tends to be less penalty being low, vs too high.
Bikerollingresistance.com kind of brainwashes folks to think higher is faster. And sure it is, on a flat surface like a roller that a wheel is forced into constant contact with. It is kind of like the limits of cfd or laminar airflow to determine aerodynamic efficiency of bikes in the real world. It is not useless, but it has limits, and is not the full picture.
Tires that are too stiff really start to cause a lot of energy loss through vibration, and worst case, springing the bike/rider into the air. But higher pressure has less crr. It really is a “baby bear” scenario, vs maximize/minimize. The trick is that baby bear varies with every road surface, and multiple times a ride.
Heck, the pros choose tire pressures for the roubaix based on prevailing winds (i.e. they optimize tire pressure based on where they expect the winning move to take place in the race). This year they ran higher pressures because the wind did not favor the race being won on the cobbles.
But like aerodynamics, it is largely an exercise in faith. Aside from repeats of the chung method, it is pretty hard to prove. For most of us. Still, the silca data is the best data i have seen, so i am influenced by it. Tom A. also independantly came across the same conclusion. Mountain bike guys knew this for years, but again, i think some were surpsised how much the same theories carried over to “smooth” road.
