The Michelin and Goodyear tire data books provide the best guidance. Clip below for your hard drive.
A 5.00-5 6 ply is fully inflated at 50 psi, no load, to provide a capacity of 1285 lbs per tire. Minimum required pressure to not exceed deflection limits is proportional to weight. So, for an RV-14 at 2050 lbs, we can adjust down a little. I don't have an RV-14 weight and balance in front of me, but for example, I'll assume 1800 on the mains at gross weight, or 900 per tire.
(900 x 50) / 1285 = 35 psi unloaded, minimum
Pressures are adjusted upwards 4% when loaded, so...
35 x 1.04 = 36.4 psi, loaded, minimum
I stress minimum for good reason. At minimum and below, you're in tube and tire damage territory. There is no downside to operating at maximum pressure, other than the classic shimmy problem on the round leg models.
The above is fact. Anecdotally, I've operating my RV-8 for 1200 hours with the same tubes, at 50 psi since day one.
At Triple Tree, I asked a Beringer rep about minimum inflation pressure when run tubeless. He declined to offer an opinion, stating inflation pressure is determined by the airframe manufacturer. In addition to the above deflection limit, I suspect running tubeless at 25 to 35 psi will eventually result in deflation if the tire is side loaded significantly, like a bad swerve or a firm arrival with one wing low in a heavy crosswind. The Michelin book does not seem to differentiate tube and tubeless, so I'm pretty sure the above calculated minimums still apply with tubeless Beringers.
I was amused by the Beringer rep's claim of tubeless superiority, which could be summed as "It's always the tube that fails". Well, yeah, that's the part which holds the air. Results are not going to be a lot better running underinflated with a tubeless wheel.
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