I inflated my RK's tires the other day using my $15 Accu-tire digital gauge, front at 36 and rear at 40 psi. Just for chits and grins I thought I'd check the pressure against the gauge on my HD air shock's pump. Well lo and behold it consistently reads 4 lbs lower than my digital gauge. Now I can't trust the accuracy of either gauge! So my question is, Who makes an accurate and calibrated gauge and how often should they be calibrated?

 

I've had the same worry over the years as I've noticed a discrepancy between gauges. On a trip several years ago a friend was checking his tires with a typical pencil gauge and I decided to compare with my HD pencil gauge. Mine was 2# lower, so we found a third gauge that showed 2# higher. So, we had three gauges that totaled 4# of difference between them and none within 2# of any of the others.

When I returned from the trip I started to research this topic and found that the AccuTire MS-4000 gauge had a good reputation for accuracy based on reviews and tests. They're about $30 retail but I found one on Ebay with a Goodyear logo stenciled on it for $12 shipped. It shows 2# higher than my HD gauge, right in the middle of the aforementioned group. I decided upon this as my standard and still carry the HD gauge on the bike but add 2# to the reading. I use it most of the time and will pull out the digital gauge mostly to check other gauges.

It is amazing that while doing this research with few exceptions the only gauges I could find with an accuracy guarantee were those designed for calibration, which are apparently designed for limited use and are too fragile for everyday use. IIRC the MS-4000 had an accuracy guarantee but I can't locate any info on that now. Since that time I've seen some Moroso dial gauges costing $40-45 that are "calibrated to within 2%," which at the pressures we use is almost 1psi. Regardless of the type--pencil, digital, or dial--accuracy statements were conspicuously missing in descriptions for these devices. You would think accuracy at least ą1# would be the standard and would be guaranteed. Most of the pencil gauges that have accuracy statements are ą2psi, and to me that isn't good enough.

For the time being I'm depending on this gauge as my standard for accuracy. If it isn't right on the money I'm betting it is very close. BTW, I checked the AccuTire against my old Progressive shock gauge and the latter reads 2˝# higher. I would trust the digital gauge over the shock gauge any day. What I've noticed about the digital gauge is that its readings are much more consistent than the mechanical types.

 

Yeah I use the digital ones from sears. I always figured its pretty accurate, but always kinda of wondered.

 

I feel yer pain, I have 4 different gauges all read different but within 5 lbs. Looks like they could get closer than that!

 

The differential between gauge accuracy is troubling considering how critical tire pressure is for handling and tire life. I slacked off for a month one time, noticed some sloppy handling in a sweeper, checked my pressure and was cruising at around 30 psi. Even after adding 10 psi, the handling was diminished until I replaced the tire (the cords had broken down some). I became a bit of a fanatic after that. Not enough though, now I'm gonna compare my gauges with each other.

 

I bought an Accu Gauge non-holding dial type way back around 1990. I took it into work, an aero-space company,
and our local cal lab did a calibration on it for me. Back then it read only 1/2 lb low of actual which I thought was
fantastic as most gauges are off by more than that. My latest Accu Gauge is of the holding type and reads too
close to the same as my "standard" to see a difference. But I still question the accuracy as it was calibrated so long
ago and has been bumped around a bit. But as we used to say in the industry, "Close enough for Government work".
I've found that most pencil gauges suck and that a digital readout doesn't add anything to the accuracy of a guage.

 

I have agonized over this myself for years. I have come across this website and based on the info they provide I will be making a purchase from them. They are all American made gauges. I am pretty **** when it comes to my vehicle tires and pressures.

 

Excellent post and something that has bothered me for quite some time. I wish there was a service that had a calibration or at least gave the proper reading so I knew just how far off my gauges are.

 

I agree that a 1% variation would be nice. Perhaps some genius on the forum could devise an accurate homebuilt air
pressure standard and post how to make and use it.
That 2% probably isn't any worse than the variation we'll get when checking our tires in a cold garage or when the
bike has been parked outside in the sun.

I've also checked my tires when I get them back from one of our local shops and find their settings to be way off.

 

I check my tires every week. I have three gauges that are all within 1 psi of each other. One of them belonged to my father and is about 50 years old. Another is an auto parts store cheapy and the third is on my tire filler. I fill to the max cold and ride.