Tire pump revisited

i bought a senco 120v nail gun compressor at home depot for $150., smallest, lightest, quietest, smoothest compressor i've ever owned.
how much does pressure drop in the cold?

 

The graph in T-SB-0020-11 Tire Inflation Pressure Compensation and Adjustment makes it look like the slope is about 1 psi for each 12°F difference between the current ambient temperature and the temperature when the pressure was adjusted.

-Chap

 

my old tyres hardly ever lost pressure. since i had the michelins put on about a month ago, so far so good. i run 42/40, so there's plenty of cushion, but i've never encouterd the tpms warning.
when it came on in my wife's hycam, it was already down to 26 psi. an anomaly, which hasn't happened again.

chap's tsb is very interesting. i wonder how many people, who run their tyres at the 'recommended placard pressure' have any idea what's happening in cold weather.

or what if you're setting pressure in a climate controlled garage, and it's a hundred degrees outside.

 

I had a terrible problem with tire pressure dropping, no matter the season with my set of Cooper GFE and my later set of Goodyear FuelMax. My latest set of Generals RT43 were installed in August when it was around 90F....lately daytime highs have been 33F. No tire pressure light yet. Still, I guess I ought to hobble out and check the PSI. Thanks, Bob!

BTW, I have a cheap 120-volt pump from Home Cheapo that looks a bit like the one in Bob's picture, except for the hose. $30 when I bought it, but now it is $24. Actually, $15 would be about right, but at least it works.



Nearly impossible to find working hoses at service stations anymore -- even the ones that cost 50-cents

Oh, I have a Slime 12v inflator, also. Got it for free during a promotion at a local hardware store. It was $15. Never used it.

 

Has one of these for years;
Sears.com
Finally died a couple weeks ago topping off the temporary spare to 60psi. It's sitting next to me at moment; until I pull out a screwdriver to take it apart.

 

I was caught between two alternatives I had gotten fed up with both of. (Three, if you count trying to find service stations with working air when you need it.)

My first try (after getting fed up with service stations) was one of the usual-suspect 12 volt inflators. It lived in my vehicle and could air up my tires anywhere, at least until the day it chawed up its rod bearing into bronze dust and threw the rod.

And that, IIRC, was before I'd had it a year, so I had probably aired the tires not quite a dozen times. (Ironically, I had chosen that one because it proudly proclaimed "Made in USA". By the time it failed and I asked for a replacement, they had dropped that claim and gone offshore, and the replacement they sent me was made in China, and seemed better built.)

But even when working, just waiting for it to top up four tires could try the patience of Job. (I was topping off SUV-sized tires back then, and could be out there listening to that racket for 20 minutes.)

And besides airing tires, they're good for nothing else (except maybe beach balls), so in order to do anything real involving an air tool, I eventually had to cave and buy a 120 volt compressor anyway. I got a four gallon pancake type.

It was "portable", but bulky and heavy enough to be annoying to jockey around. I don't have a lot of dedicated workshop space, so it pretty much has to live in an unusable spot and get dragged out when needed, then emptied and put away again.

For a while, I was doing that to top off tires, just because it could fill them faster and didn't make the same grating racket as the 12 volt inflator. But figuring in the hassle of dragging it out, waiting for it to fill four gallons of air, topping off four tires in a matter of seconds, then carrying it back in, emptying most of the four gallons back out, and putting it away again, the annoyance factor was pretty much a wash between the two alternatives.

So at last I got fed up with both approaches, and found a refurbished Viair 450C. It runs on 12 volts, permanently wired (23 amps), and is enough of a non-toy to have actual duty cycle and CFM ratings. The rating is less than half that of the 120 volt pancake compressor, but honestly, that ain't bad for something small enough to live in the car.

I bought it from an outfit that sells locomotive horns to car owners. I have pretty much zero interest in making my Prius sound like a locomotive (despite the woman on the front of their catalog, who looks like she'd be happy to explain their logo), but compressed air is handy.

In my Gen 1, I just suspended it in the trunk with coated wire rope. (If you're wondering why the compressor was on the passenger side—the non-battery side in Gen 1—it's because the inverter lived on the other side, hung by wire rope in the same way.)

Hanging them just out of the way of the trunk lid hinges was the only trick.

But then my Gen 1 got clobbered and it was back to the drawing board to find a way for the compressor to live in a Gen 3.

Out with the original plastic jack-and-lug-wrench holder (jack is wrapped in cloth and just living in the plastic cargo tray with other tools), in with the compressor. Its reservoir is the spare tire, which it dutifully tops up to 60 psi whenever necessary when the car is READY. The safety relief valve shown in the end of the manifold there is a 65 or 70 psi one, and the adjustable pressure switch was set for just below that so the compressor stops before the valve starts tooting. The blue hose runs to the valve stem (wouldn't it have to be on the side of the wheel facing down), where it attaches with one of these Silca thread-on Schrader chucks.

The hose barb on that fitting is a bit narrow to fit US 1/4" hose tightly (it's made for Silca's own air pump hoses, which must be narrower). I got lucky with the blue, coiled nylon hose that I found at Menards, which is narrow enough it has to be softened with a heat gun to slide onto the Silca fitting and, once cooled, it is on there.

The gray hose is a 25 footer found at Harbor Freight, billed as polyurethane to stay pliable even in cold temperatures, and that seems to be true; it's been pretty cold this week, and still uncoiled and recoiled nicely. The yellow/black wrap is to protect it where it goes under the plastic cargo tray. The coil lives in the small mini cargo tray on the left, accessible under the small plank without having to pull up the main deck board. It's long enough to comfortably reach all four corners of the car, use with a blowgun end to blow away junk around the engine, etc.

Holding down the spare tire involves threading an M8 double-ended stud into the hole originally for the plastic-handled hold-down bolt, then a piece of wood over the stud, and an M8 coupling nut tightened down on the wood.

Then the original plastic-handled hold-down bolt threads into the coupling nut, through a 23 cm length of aluminum to hold the compressor down. The other end of the aluminum just hooks through one of the openings in the steel wheel.

The underside of the aluminum, where it bends over the compressor, is brushed with clear Plasti Dip to make it grippy enough when starting torque tries to twist the compressor. The end that rests against the wheel is dipped too. I made the bend by just resting the straight piece over the compressor and tightening the hold-down. That way, it is not over-bent, and still does put a secure force on the compressor.

Along with the hose coil in the left mini-cargo-tray, there live a blowgun attachment, and one of these nice trigger-actuated, thumb-chuck inflators with a big, easy-to-read gauge.

Now topping off tires, or blowing tree gradoo from around hatch edges, etc., is as easy as reaching in the corner and pulling out the hose. Topping up a tire that's a couple pounds low takes only seconds. The spare-tire "reservoir" holds enough air to top up four slightly-low tires with the car off, and then the compressor will run for several seconds to make it back up when the car is made READY. If more air than that is needed, the car needs to be READY first, so the compressor can keep up.

By itself, this setup won't run most air tools well. Not only is the 60 psi spare tire pressure a bit low for most tools, the Schrader valve restricts flow. A blowgun works ok because it's typically used in small puffs, and the pressure in the hose recovers between puffs.

If I'm setting out on a trip where I might use tools, I now have a portable, lightweight aluminum, four-gallon tank. It's small, much lighter than steel tanks, and easy to toss in the back if I might need it. It has its own safety valve and pressure switch, inlet hose, outlet hose, and regulator, so to use it, I can just move the compressor outlet hose from the spare-tire manifold to the aluminum tank inlet hose, and unplug the relay connection from the spare-tire pressure switch and plug it into the tank pressure switch. That'll pump up four gallons of air at the usual 125 psi, enough to do some useful work with an impact wrench, for example, if you don't mind resting for a couple extra minutes for the tank to refill, compared to a 120 volt compressor. (When compared to having to go in the house and drag out the 120 volt compressor, the little one that's always ready to go wins, a lot of the time.)

At the power-distribution thingy, one of the Maxi fuse slots, shown unused in this picture, gets a 30 amp for the compressor itself, and one of the switched, ATM fuse slots gets a small, 1 or 2 amp for the pressure switch and relay.


-Chap

 

Yeah, I know, off-limits, but:

I used the Schwinn today. I had four freshly re-tired rims in the family room, putting some wax on them (they go back on our son's car in spring). I didn't even bother asking Costco to bump the pressures, they're sticklers. So anyway: four tires, all needing to be raised about 8 psi. Didn't take that long, about 50 pumps per?

 

I've always used the hand pumps I use for all my bikes, but recently after doing the tyre-check-thing (every month or so) I thought "…this is the 21st century fer Christ'ssake!" …and so I invested in one of these: (…and I use it for the bike tyres as well!)

 

I bought a digital "Slime" brand compressor for each of our cars. For the price, they're definitely much better than others I've had over the years.

 

I bought the Harbor Frieght one and if it works once I will be happy. It's only for emergency.

 

Finally got around to taking it apart.
The brass pin that held the spring metal flapper/diagram in place came loose. After, bending the flapper back into shape and hammering the pin back in, the compressor works, and should give me a few more years to the decade plus I've had it. Just need to replace the rubber feet that were placed over the case screws.

 

I use the bicycle pump most of the time at home and carried a cheap Slime inflator in the car for years. The Slime was slow but it held up well and got the job done. I left it in the back of our old 2002 Buick when we gave it to our son.

Now I have a Black and Decker Air Station from Pep Boys. It's combination AC/DC and has an automatic cutoff when it reaches your desired tire pressure. Sounds good but it does have some serious design flaws. The electrical chord is so short an extension chord is mandatory and it's necessary to take the 12v chord out it's storage location to get to the on/off switch behind it. The unit does work as advertised, though, and I don't have to use it very often so I won't bother getting something more convenient to use

Black & Decker High Performance Air Station and Powerful Inflator | Tire Details | Pep Boys.

 

I have a Slime and tire plug equipment in each car, but it's not as fancy as the one @bwilson4web has. No preset pressure. So far, I haven't needed either. But I did need to plug and pump a motorcycle tire a few years back so I could get home. Sure glad I was prepared!

 

First opportunity to use the revisited tire pump in a good-Samaritan capacity ... on the way to work, passed a guy standing outside his van staring forlornly at a thoroughly flat tire. Brought up to 44 psi in a minute or so.

-Chap

 

That's the pay off, when you get to use it, help someone out.

It's that Viair 450C providing the air?

 

The very same.

 

A funny thing happened on my way through Ohio:



It would have been a textbook application for a good tire plug kit, which I had even thought about buying back in April, but had never quite pulled the trigger, so there I was a couple hundred miles into a 600 mile trip, on the eve of the 4th, and it looked like the only place even open on the 4th to repair or buy a tire would be Walmart, so I drove there on the donut spare and camped in their lot until the tire dept opened.

Thanks to the on-board air, the donut spare was exactly at 60 psi when I took it out at the side of the road. That was handy.

I realized there was one thing I hadn't provided for when I designed that system. Once the spare tire is in use, the on-board air becomes unusable. I used the spare as the 'tank', and the hose to the spare's Schrader valve is just dangling with an open end when disconnected from the spare. For that situation, I would need something to plug the end of that hose, like a Schrader "tank valve" and a pipe cap:



So, that's added to the 'accessories' bag now. I haven't tried it out yet, and I'm pretty sure the behavior won't be pretty (without the reservoir capacity of the spare tire, probably really rapid cycling on the pressure switch), but at least it may preserve some ability to use air, even while the spare is in use.

-Chap