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!

 

[Aushiker]

I have just come back from three days of bikepacking on my Riese and Muller Supercharger 2. It has 27.5 x 2.35 (60-584) tubed tyres. For the off-bitumen riding (forestry roads and single track) I dropped the tyre pressure to 25 PSI ( the stated minimum on the tyre). That worked well for me on this ride.

If I had taken my fatbike with 4" tyres, well, I would have gone lower again, probably sub 10 PSI, but that is tubeless.

 

[mycalsuite]

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!

You can definitely go lower than 40 psi, especially at your weight, based on my experience running identical 700x40 tires with tubes. Something in the mid-30s should still be safe for you and your bike, weighing 160 pounds plus the bike, while also providing you with additional comfort and traction over gravel. The biggest concern with tubes is pinch flats; the risk increases if you start to go into the low 30s and run into potholes or sharp edges.

To find the balance between comfort and avoiding bottoming out on harder terrain, try starting at 38 to 40 psi, riding for a short while on your typical gravel, and then lowering the pressure a few psi at a time.