I definitely need a better low pressure gage... mine I think measures a half pound low. But don’t have a better gage to check it against at the moment.
There is 27.7” of water column in a PSI, so in theory, if I have something like 110.8” of tubing that is filled with water, connect it to the gauge, it should read 4psi, when the tubing is stretched out vertically, like out a second story window. I think I might make this rig this evening and test some gauges.
Here we go: Roughly 109.3” of water column. The gauges that i wanted to test have roughly 1.5” stems off of them. So the total to the actual part that measures pressure should be 110.8”. I used a small funnel help fill it with water. There is a schrader valve from a tubliss system at the bottom, I left the rim lock on it to provide some weight so the tubing stayed straight. Initially I tried dumping water straight in but the surface tension of the water kept it from filling. So I put a few drops of dish soap in the funnel to break up the surface tension. The drops sank down the tubing and broke up all the air pockets. Here is my selection of gauges that I may use for low pressure. The one on the left goes in my dual sport and sometimes I may run as low as 5 psi in the rear of it. The next one lives near my air compressor in the garage, you may notice that the needle is at 2psi right now. Moving further to the right is a newer Slime gauge that I keep in the moto van. Finally, the furthest right is one that also was in the moto van. Surprisingly, the digital one was accurate. Right at 4 psi. It will read in .5 increments. The Slime gauge that is stuck at 2psi actually read 6psi. I would say that is accurate enough. I put a label on it to remind me to subtract 2psi from the result. The next slime gauge read perfectly. Finally the pencil gauge only read 1.5psi. So it went in the trash.
I tried to. Unfortunately the 0 - 15 psi gauges are backordered right now at the Tryals Shop, so I am patiently waiting for Mike to ship one out to me. Great guy, thought I'd be happy with a 0-30 gauge instead and is making it right for me once the new ones come back into stock.
Yeah, after 1 hour of mowing my riding area I rode for 2 hours. Mianly 3 20 minute sections of hard practice followed by adjustnents to the bike. Followed by two hours of hauling dirt as some of my railroad ties were moving and needed some support. Then I 2 did a water test, my 220lbs moved 15000 gallons less than 1/128 of an inch.
If you have some time to kill, refreshing knowldege https://www.thearchitectsguide.com/articles/best-tire-pressure-gauge https://ultimatemotorcycling.com/2020/04/28/under-pressure-air-pressure-for-motorcycles-that-is/
Joes Racing 32305 (0-15) PSI Tire Pressure Gauge https://www.amazon.com/dp/B000VZF6YE/ref=cm_sw_r_cp_api_i_n-L-Eb193S7SR These work well. Available at most automotive performance shops. Come in 15, 30 or 60 psi varieties.