yup, 31mm external width. If you follow the rule of 105%, then keeping inflated tire width around 29mm (as measured) is better for aerodynamics.
The FAQ on that page states:
I’m also north of 200lbs and have the 32mm external width Aeolus Pro 3V and current tires measure 38mm inflated (35x622 tires). I’m going to try 32c and 30c tires next.
I’m of the same opinion, my Pirelli Cinturato Velo tubeless measure out to 38 and look ridiculous at Wed night worlds. But it doesn’t seem like I’m giving up too much, and they were fantastic on California gravel/dirt roads. For example on a local ~10 minute Strava segment coming back into town with a 10mph tailwind/crosswind assist:
- Aeolus Pro 3V with 35c Cinturato Velo tires did 10:32 / 24mph / 246W in June 2021
- Deeper Enve 5.6 with same tires except in 26c did 10:23 / 24.3mph / 256W in April 2020
different bikes with similar geometry, and that segment runs 1.8 miles west, then 1 mile north, and 1.4 miles west and the tailwind was West / Southwest. Different days but similar wind conditions. Not same-same testing but similar times.
For Wed night I definitely want to run with some faster rubber, the Cinturato have incredible puncture resistance and roll faster than Gatorskins, but definitely not the fastest tires. So I’m going to try two race tires in 30 and 32. For everyday riding on crappy roads I’m very happy with larger volume tires.