Properly inflating tires

[m@Robertson]

Yow. I hadn't thought about water vapor affecting tire pressure. Now I will.

I wouldn't sweat it. My original point in this was that using nitrogen vs. Terran air in tires provided only a miniscule benefit even on tires that are as big as car tires. It only matters enough to make sense to professional race teams.

 

[PCeBiker]

It does remind me of a claw hammer, but when I googled "hammerhead chuck" and checked Amazon, all I found was a chuck to secure drill bits.

"Quick Release" worked for me,..

 

[spokewrench]

Yes. Its a teeny puddle on a 5 gallon tank. Half a teaspoon tops in my garage a mile or so from the seashore. More if the tank is bigger, I suppose. I only empty out my own tank and its a 5.

In summer, I think I may get an ounce even if I pumped up the tank just long enough to top off tires. Air can hold 6 times more water vapor at 95 than at 40

No. The water is vapor. Naturally occurring. Ever-present. Its the reason water filters on air compressors exist.

How do you filter water vapor? At 50 F, the vapor pressure of water is .34 psi, meaning air can't be more than 2.3% water molecules (at 100% RH). If my compressor sucks up that air at 100% humidity and squeezes it into a tank at 147 PSI ( 10 atmospheres relative, 11 atmospheres absolute ), it can still hold only .34 PSI of water vapor, but now it's only 0.21% of the far greater density of air molecules. Compression has squeezed most of the water vapor out of the air. Now if this air expands to fill a tire to 40 PSI (54.7 absolute), the air including the water vapor will be 33.8% as dense. The relative humidity will be 33.8% and the vapor pressure .12 PSI: much drier than the ambient air.

PC explained how water gets into traps. It's mist. That hadn't occurred to me because normally when the temperature drops to the dew point, moisture condenses on the grass while the air remains clear. Once in a while there's fog. If the droplets float in the air, they must be very small. If I can see 100 feet, there must not be many of them. In a compressor tank, I assumed any mist would immediately settle, but I guess if the volume of air in and out were high enough, it could carry droplets out.

No you are mis-quoting me. Go back to Post 35 where I mentioned performance started decreasing right at around 50 psi. That has nothing to do with the potential for pressure increase you are talking about.

In Post 35, did you not say this? "Pressure change in tires aired up with air is due to the naturally-occurring moisture in the air."

Initial cold pressure tends to be the same, but maybe gets bumped up or down depending on weather. The only mind you paid to humidity was when you put the water filter on your air compressor line.

Reduced from say 52 to 46-48. What you were actually doing was reducing pressure so the edges of the tire tread stayed on the ground. Road racing slicks inflate like a balloon. Much more so than street legal tires. So as pressure increases you see wear completely stop on the outer and inner inch or so of the textured (slick) tread. That decreases surface contact, with the obvious effect, so you decrease pressure to lay the whole tread back on the ground. So yes you cling to the pavement better because you use all the rubber available again.

In Post 40, did you not say this? "To top all that off, running at Laguna Seca (coastal California versus) Big Willow (main track at Willow Springs Intl Raceway in Rosamond, CA - in the desert) cold air pressure for the start of the day is different given relative humidity. Its just as cold but of course the humidity is different."

I wasn't familiar with changing tire pressure according to relative humidity, so I looked it up. More than one source said it's because traction on paved tracks is poorer in high humidity, as I knew from experience. I didn't find anyone who said, "Pressure change in tires aired up with air is due to the naturally-occurring moisture in the air."

 

[spokewrench]

"Quick Release" worked for me,..

Not for me. As I said, I'd lose about 2 PSI putting it on and about 3 PSI taking it off. On a 4 L tire inflated to 45 PSI (60 absolute), each on/off cycle lost about 1.75 L at standard pressure. That might have worked if it had been consistent, but hissing losses are different every time.

I ordered a brand that had done very well for me from 2018 to 2021. The new one was so bad that I thought it was different from what I'd bought before. I compared and found it identical. I think the difference was that I'd used the old one a couple of years on car and mower tires before I got an ebike. On heavy vehicles, you can use force to get a chuck on and off fast. That wear got the old one to slide on and off more easily. Reaching between spokes on a 70-pound bike is trickier, and a new one had more friction going on and off.

I discovered that they make ball chucks with barbs, so you don't need a line with pipe threads. I bought this.

Amazon.com

What a difference! No hiss! No apparent loss! Now I could test, inflating an 8 L tire.to 30 PSI. I'd unscrew the core and put the chuck on when I no longer felt air coming out, inflating the tire from 1 bar (standard pressure) to 3 bars, requiring 16 L. Each time, it took 2.2 minutes, for 7.3 L a minute. The specs said 30 L a minute. They also said the 22 Watt hour battery would run the pump an hour under load. 7.3 L per minute is more in keeping with the specified run time.

It cut off as it finished filling the tire the 7th time. Compressing air extracts heat. I suspected that this was a thermal cutout. I came back after an hour and screwed the core back in. The pump now worked fine, but this time, the tire took at least 5 minutes to inflate. Then, each time it shut off at 30 PSI, the tire would lose pressure rapidly. I had a hunch based on previous experience. I took a break. When I returned, the pressure was 25. When the pump brought it to 30, it stayed.

My going away for an hour to let the pump cool had let air seep in past the beads, collapsing the tube. That meant I had to pump more air than the first 7 times. The expanding tube pushed the beads against the rim, trapping air. To further inflate the tube, the pump had to fight pressure from the air trapped between the tube and the tire. After it cut off at 30, air outside the tube would continue to seep out, letting the tube expand and reduce pressure. It wouldn't pump up properly until the trapped air escaped.

It had taken more than 20 minutes of run time to inflate that 3.3 inch Radrunner tire 8 times. The state-of-charge indicator has 3 bars, and 2 were still lit. It looks as if the specs are correct in saying the battery will run the pump an hour under load. Wow!

The specs say the pressure sensor is accurate to plus or minus 2 PSI. I've found digital sensors to be more accurate than that. With a ball chuck, this one agrees exactly with my other gauge. I think the manufacturer found inaccuracy because he'd tested the pump with the OEM chuck. If he tested tire pressure with a calibrated gauge and then air hissed as he connected the pump, the pump would show a lower reading than the calibrated gauge. If he pumped up a tire, took the reading, and air hissed as he disconnected the pump, the calibrated gauge would show a lower reading, as if the pump gauge sometimes read a couple of PSI higher and sometimes a couple of PSI lower than a calibrated gauge.

Why isn't there a Carl Norgren Day? If children were properly indoctrinated each year, everybody would know better than to use anything but a ball chuck.

There is something almost as good. In the 50s and 60s, I rode on 1.6 liter tires inflated to 60 PSI. A little hiss checking pressure would have meant hand-pump hassle. It didn't happen because I used one of these.

Amazon.com

They still have a reputation for accuracy and durability. The long shaft makes it easy to reach between spokes, see that your angle is right to contact the valve squarely, and press. Your measurement is mechanically recorded for analysis.