How low can I go? (PSI- and not pinch a tube)

[Rexlion]

I just got some WTB Vulpine gravel tires put on. 700 x 40. WTB website recommends 25 to 50 psi, but I assume that is for tubeless use, and I am still running tubes. (The bike shop tech didn't think my rims were compatible with tubeless, based on the inside ridges.) The tech said he wouldn't go below 40 psi. I'm not doing any single track, just gravel/dirt roads where one never knows when some loose stuff might be encountered, so I'd like to be aired down. What do you all think is the lowest pressure I should ride on? (If it matters, I weigh 160 lbs and the Yamaha CrossConnect is something like 55 lbs.)

The ebike came with road tires that called for 60 to 80 psi on the sidewall. Talk about a stiff ride!

 

[Stefan Mikes]

The tech said he wouldn't go below 40 psi.

He's right.

A conservative calculator
A more liberal calculator (use Gravel for type)

 

[Rexlion]

Very interesting calculators! Thanks!