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  #21  
Old 12-22-2008, 08:54 AM
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BTW I'm jazzed to see your rig in motion. The last time I saw it you had the instrument cluster torn apart. IMHO you have one of the sweetest rigs in the nation. Beautiful!
Oh pooh.....now you did it. We just finally were able to get Bill's hat to fit his head again and you just went and popped the adjustment band right off.....there will be no living with the man again for months.....
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  #22  
Old 12-22-2008, 09:19 AM
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part of the reason i set up my york was because i was kinda getting tired of the pressures in my tires getting so out of whack after wheeling. did it make a huge difference to switch to air instead of CO2? yeah... could i even notice when my tires were 5psi high or low? no.. not really.

i air down with a cheapo, 99 cent analog dial guage i got from home depot in the checkout isle.. i air up with an ARB super duper dial guage i paid a lot for. They both read right on.

Have I been totally screwed before thinking i knew my tire pressures? you bet your a$$. For about three autocrosses, and two drivers' ed's in a row last year I could not for the life of me figure out what the hell was wrong with the CRX. It just handled like crap. I finally noticed the guage i was using was about 7psi off in most cases, and 10 in some. yikes. now I at least cross check my new guages with another old one before calling it good.

pretty enlightening. I got lazy and used an old guage i had rolling around in the car instead of my nice ones and it bit me. I guess any of them could be off though.

FWIW, my locker acts really funny if the tires aren't within a few PSI on the road... but normally they go up and down together. Off road, it is always locked anyways it seems.... and tire pressures seem like they always end up all over the place.
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  #23  
Old 12-22-2008, 09:55 AM
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Back to the issue of Nitrogen. My CO2 setup started as a Nitrogen bottle. (it was leftover from a job, FREE) I couldn't believe how fast the pressure dropped in the bottle. Later I found out that the same size bottle will hold 3 times the CO2 as N. CO2 compresses down and turns into a liquid where N does not. I traded my bottle in for a CO2 bottle for just the cost of a fill. They also converted my regulator for $6. (High Plains Welding)
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  #24  
Old 12-22-2008, 12:18 PM
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You are right on, when I got a bottle of N we were only able to fill up 5 cars. Two sets of tires were small, like mini cooper tires. The others were 265/70/17. We were barely able to get the last set done.

The same size C02 would do 20 or so fill ups.
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  #25  
Old 12-22-2008, 07:53 PM
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Rzeppa Rzeppa is offline
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Whenever I read threads about CO2 versus N2 I have to chuckle a little. Yes, they have different molecular weights and have different specific heat, however they both obey the laws of physics: PV=nRT, where P=pressure, n=number of moles of the gas, n is a constant, and T is temperature in Kelvins. They will both change pressure EXACTLY the same with the same change in temperature for our purposes.

There have been claims that Nitrogen is better than plain air with it's oxygen and water, in terms of holding pressure for extended periods of time and degradation of the tire rubber compound, but for our purposes, N2 has no real-world advantage over CO2.

FWIW, when calculating a pressure change in a gas due to temperature change in a fixed volume, you must always use Kelvins for your ratios. To get Kelvins, simply take the temperature in C and add 273 (or 273.15 if you want to split hairs). Thus, if you start out with 30 PSI at 0C (32F) and warm it up to 20C (68F), the warmer tire pressure will be 30 PSI * 293 K / 273 K = 32.2 PSI. Kelvins cancel and you are left with PSI as your units (one of the easy error-checks when formulating equations in physics).

However, and this is REALLY important, there can be HUGE differences in gauge accuracy at different temperatures. This applies to both mechanical gauges and especially to digital ones. If a digital gauge does not have temperature compensation built in (which costs more $$ to build), it will be all over the map at different temperatures. I have designed with pressure transducers which require in excess of 2300 ppm of compensation requirements. Not only that, the Temperature coefficient will vary from one transducer to the next, requiring individual calibration (read=expensive production costs).
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  #26  
Old 01-23-2009, 03:05 AM
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Steelman Digital Tire Inflator Review. I wanted to post up with info about this a while ago but have been busy. Anyhow, the short version is I don't recommend it. Looks cool but that's about it.

Packaging





Front. I like the rubber boot that it came with. Nice and thick.


Back side Easy access to change the two AA batteries.


A closer look at the face. The plus and minus buttons inflate or deflate.


I changed out the black hose with a red flex hose and put a swivel connection on it.


A closer look at the ends


PSI readout


Bar readout


KPA readout



Even though the Steelman has some cool features such as backlighting and an accurage gauge, I ended up shipping it back for a refund. The little things about it, which I'll talk about later, just didn't make it better in my opinion than a regular ole $13 inflator like this one.


The above Rand inflator is the one I've been using for the past year and I really like it. For one it has a dial gauge that faces you when you pull the trigger. The trigger has a long lever making it easy to pull even with high psi. The dial gauge is fast and reliable. I added a swivel connector to mine for the heck of it but I really don't think it needs one.


The Steelman has a couple of things I'd like to see changed before considering it to replace my cheapo. The + inflate and - Deflate buttons are too hard to press especially when running around 225 psi. I didn't like pressing hard on them for a few seconds. I think I'd really dislike it trying to hold it down for 5 minutes.

When I aired down to 15 psi and tried to get a reading from the Steelman the first three attempts showed 3psi. The fourth time it showed an accurate reading but several readings later proved unreliable. It seemed to be either dead on or way off. It didn't have the problem when my tire pressure was up around 30psi.

The Euro style chuck is heavier duty than most except for where it counts. The spring is too weak causing it to lose it's bite into the valve stem threads. Again the Rand did better.

It has an audible beep when you reach the selected pressure or above. It got irritating quickly. If you were able to hold the button and it stopped inflating automatically with an audible this would be nice but it doesn't automatically stop inflating so as you back off to deflate you keep getting the beeping. It's too bad the buttons were not solenoid controlled for an easy touch and automatic stop.

The backlit display can be turned off to conserve battery power but the default mode is on. So every time you use it you have to shut off the display if you don't want to waste the batteries in the daylight.

So while it looks really cool and has a good idea behind it the performance just doesn't hold up for real world use. Kind of a bummer I really wanted to like it.
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  #27  
Old 01-23-2009, 08:11 AM
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BTW, Glen, thanks very much for your kind words.

No worries, UB, God seems to have on His project plan a step-by-step rollout of a series of events designed to preserve my hat size.

FWIW, that darn cool pressure gauge is only as good as the batteries. On the snow run, I had discovered at its first attempted use that my center console - full of junk - depressed the button sufficiently to drain the battery despite the auto off feature.

Back to mechanical.
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  #28  
Old 01-23-2009, 09:34 AM
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i've found the best guages to be the 2.99 specials you buy at walmart. i've found the worse were any guages you bought at harbor freight.
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  #29  
Old 01-23-2009, 09:56 AM
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Interesting, since they come from the same place.
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