Tire Pressure Story...is YOUR tire pressure correct?

I have 3 tire pressure guages...2 regular ones and one digital. Unfortunately, they all give me wildly different readings. So I went to the gas station to see which one was "correct." Unfortunately, I got a 4th reading that did not match any of the previous 3 readings (no matter how many times I tested all side-by-side). So, frustrated, I went to Discount Tire to have them give me the definitive answer. The guy tested the tire pressure and again with side-by-side comparisons, we now had another different reading. So they tested some of their other guages...we found that every one they had gave a different reading! After many tests by several tire experts, we finally decided upon 2 guages that matched...and they gave them to me for free.


p.s., I learned that it helps to pull the stick in and out several times before you use it (no jokes please--too obvious).

Has anyone else ever found this...or tried comparing several guages?

Is there any way to get an accurate reading?

(test your tires cold)

Best, Kevin.

 

It is always the same with all guages. Just from experience, don't use digital guages because the reading is affected by the battery voltage and don't use these stick or pen type guages, they are never accurate. Get your self an analog guage from a top brandname specialized in industrial guages and stick with it and do not compare it with other readings from other guages. You will only confuse yourself. Slight differences are not a big deal.

 

As Tarek said, stick guages are not always a real reliable piece of equipment. You can go on line to any of the race eqiupment and parts suppliers and get a good dial guage with a flex hose and bleeder valve for not a whole lot of money. That's the way to go esp if you are enough of a driver to be sensitive to small changes.

 

I've got remote sensors mounted on each wheel that measure both temperature and air pressure inside each tire. They signal their data to my cockpit in realtime, however, they only match up with my professional analog hand-held air pressure gauge when the tires are warm.

Most hand-held tire pressure gauges have no adjustment for internal tire temperature, so because of that omission you are going to get varied readings from different gauges under different conditions even when your air pressure remains reasonably constant.

 

For years I've used the Intercomp 0-60 psi 2" analog gauge and would highly recommend it. For $29.95 it has accuracy within 1.5% across the range. In the Trans-Am Series, we had one as backup for the $400 Intercomp digital gauge used as the official tech pressure gauge, and although the analog did not read in 10ths of a pound (like the digital), it was dead-nuts accurate when compared to the digital.

You can find it here - www.pegasusautoracing.com

 

As Brian said, if you sense pressure variations in your driving and you do need a very accurate pressure gauge, get a liquid filled pressure gauge. The liquid is Glycerine. These liquid filled gauges have superior performance and are resistant to temperature, vibration, shock,..etc.
I have one of those with a flexible hose and a bleeder valve. They are bit on the expensive side, USD 100-125, but very accurate and will last a lifetime. These can also be serviced and calibrated if needed.
Here is a link to the liquid filled tyre gauges:
http://www.demon-tweaks.co.uk/products/ProductDetail.asp?cls=MCYCLE&pcode=MSD20215&cc=usd

 

Yeah I would do as Tarek says

Purchase 1 good quality gauge and throw the others in the bin.

If your really worried about the tyre pressures on your car, I would recommend filling them with nitrogen as it is a more stable gas at higher temperatures than compressed air is

 

throw the stick gauges away-

http://www.longacreracing.com/catalog/catlist.asp?catid=8

I have used these products for years, both racing and on the street. Can't beat them.

 

Not to let the "air" out of your statements, I had given up on the "stick" a long time ago, and this has nothing to do with age!!

I purchased a digital gauge from Griots which has been quite accurate, and I think it was only $10.00 on special.

For some reason they don't offer this one any more.

BTW, Kevin, since your car came from the East coast, it might be best if you exchanged the air in all the tires completely with what we have here!

 

Consumer's Reports tests tire pressure guages about once every three years or so....they found little correlation between one type of gauge being consistenly more accurate (stick, dial or digital) than another. You will have to review the article to see the specific brand/models that were most consistant and accurate.

 

"Gauge" pressure is the difference between the tire and the ambient air. Air pressure varies. Tire temperature varies. Gauge calibration varies.

Absolute pressure would be a bear to measure. You tweak for handling anyway.

The important thing is to get one good gauge and use that one all the time.

I also keep a logbook in each of my cars -- when I add oil, change oil, or adjust tire pressure, I log it. And I use the same gauge. Then I can return to baseline and/or tweak as needed for understeer reduction, etc.

 

All very good statements, and this is why I only use the one digital gauge I mentioned.

 

In your 348? Pics! That sounds pretty trick. I'd love to see how hot (or not!) my tires get on track when I'm pulling into the paddock. I have the PeterS infrared device now (which works wonders on Luca's diaper, as previously mentioned), but your system sounds like more fun.


dp

 

cool what sensors are those? tell us about it.

 

This stuff is cheap, easy, and good. It accurately measures tire pressure compared to my hand-held gauge, and measures internal tire temp as well. The central computer unit is mounted in a huge box (see pics below), but whn I opened that box, the electronics and the display were tiny (and mounted together).

So I discarded the OEM box frame and simply slid the monitor/electronics into the pocket on my 348's driver-side visor. This required that I cut a small amount of leather out of the Ferrari visor, so I paid $10 for a 348 visor being sold on eBay (easy to go back to stock this way).

The monitor/electronics reside inside the visor pocket, but are visible through the hole that I cut in the leather.

I routed power into the unit via the side/overhead leather cover pieces (lots of empty space inside there). So when the car is on, the tire pressure monitor is on in my driver side visor.

I've got the monitor programmed to beep a warning if tire pressure falls below 30 lbs or tire temp rises above something like 95% C (actually, I've forgotten what specific value I set there). Flip the visor down and then I can see the actual values.

The tire pressure systems costs about $75 here, and there are cheaper sources out there: http://cgi.ebay.com/ebaymotors/MERCEDES-BENZ-ALL-TIRE-WHEEL-PRESSURE-MONITORING-SYSTEM_W0QQcmdZViewItemQQcategoryZ33746QQitemZ8020028276QQrdZ1

So buy the unit, take it out of its gray plastic case, cut a small window hole into your driver-side visor, slide it into your visor pocket, and then mount the four sensors onto your wheels.

For less than $100 and a couple of hours of piddling with installation and custom pressure/temp programming you'll have real-time tire pressure and tire temp as you drive.

You'll never have to manually check your tire pressures again.
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Except for the cutting of a $300 visor, it's pretty cool. I suppose any leather shop could recover it whenever necessary,

Do you have pictures of the tire mounting devices? They look gigantic too.

 

There are additional pictures on that eBay link that I gave above, including of the tire sensors.

 

I apologize for being a moron.... but you place a chip on the wheel then remount the tire? Does it affect balancing? (I assume the you'd need to re-balance).

Also, as the tire spins at some ungodly and highly illegal speed, aren't these prone to be pulled off by centrifugal force?

Pretty cool. How does the chip communicate with the other circutry? Is it like an RFID kind of device?

 

The sensors, 1 per wheel, are mounted around the circumfrance of said wheel with metal straps. People have a tough time throwing off the *plastic* straps that hold on your rubber axle boot covers, much less throwing off metal straps wrapped around the wheel.

Yes, this impacts balancing. Yes, you need to re-balance. Yes, the tire must be dismounted to install each sensor.

Each sensor has a 5 year battery in my el-cheapo model. More expensive versions use the motion of the wheel to power the rfid transmitter, much like some watches use your body motion to power their time circuitry.

I just figured that I'd never have tires lasting 5 years, so what did I care about the battery?!



One potential caveat, though: if you use your tire-inflation-can to fill up a low tire, the foam will destroy (so people tell me) the tire pressure sensor inside. My own opinion, however, is that you'd just have to dismount the rubber, clean the sensor, and remount the tire.

 

Cool. Now I understand! Yeah, 5 years on a single tire would be pretty amazing. Mine last about 6000 miles. Maybe.

 

Ha!

Hey, at least you've got someone to ask. I had to guess at all of this to do it right the first time.