Adding air to tires
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,577
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From: Overland Park KS
Adding air to tires
This may be old news to others, but I have always struggled with different pressure readings between my hand held tire pressure gauge, the compressor gauge and the in car dash reading. I was surprised to find that putting the car in the accessory mode and starting the compressor that the TPM is very responsive and that I could watch the dash and turn off the compressor when the desired pressure was reached. In the past I thought there was a delay in the TPM readings. Sure is a lot easier than guessing how to compensate for differences between the three readings.
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Nov 12, 2024, 09:22 AM
Race Director
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I'd trust a quality tire gauge (not a $2.99 pencil gauge from AutoZone) over the built in TPMS sensors.
Safety Car
Joined: Jun 2006
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From: Ashland, OH
This may be old news to others, but I have always struggled with different pressure readings between my hand held tire pressure gauge, the compressor gauge and the in car dash reading. I was surprised to find that putting the car in the accessory mode and starting the compressor that the TPM is very responsive and that I could watch the dash and turn off the compressor when the desired pressure was reached. In the past I thought there was a delay in the TPM readings. Sure is a lot easier than guessing how to compensate for differences between the three readings.
CF Community Team
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From: Charlotte N.C.
Instructor
Joined: Sep 2024
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From: Phoenix AZ
2024 C8 of the Year Finalist - Modified
I feel the same. I buy quality gauges, try to keep the pressure within a pound or two of 30 cold, but it can be frustrating watching the TPMS readings fluctuate. I trust a quality gauge and use the TPMS to warn me of an emergency while driving. Got a little nail in my right rear now that I know Discount is gonna decine to patch (right on the inside of the first line of tread), and I hate to swap out two new rears with only 12K on these.......only losing a pound a day, so dealing with it for the moment.
CF Community Team
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From: Charlotte N.C.
Pro
Joined: Jun 2011
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From: Michigan
FWIW I think the inexpensive dial gauges are repeatable, they're just often not accurate / not calibrated correctly. I have one that is basically 5psi off, to get 35 in the tire you need 40 on the gauge. Knowing that, it's fine. From what I've read it's really common with them, but they're repeatable. The stick style ones have another variability in how they are used on top.
Doesn't matter much to me anymore since I picked up one of the little 20v Dewalt compressors. You just set the thing and it runs till it hits the setting, and so far it appears to be very accurate and consistent. Also works as a air pump for airbeds and such. Pretty happy with it. The Milwaukee ones are supposed to be good as well.
Doesn't matter much to me anymore since I picked up one of the little 20v Dewalt compressors. You just set the thing and it runs till it hits the setting, and so far it appears to be very accurate and consistent. Also works as a air pump for airbeds and such. Pretty happy with it. The Milwaukee ones are supposed to be good as well.
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Race Director
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From: Bonneville Salt Flats
Over the years my experience has been and still is that GM's on-car systems are not particularly accurate or reliable. I always use and rely on Meiser handheld gauges on the street and when racing. 
E-Ray, 3LZ, ZER, LIFT
Joined: Sep 2007
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From: NE South Carolina
FWIW I think the inexpensive dial gauges are repeatable, they're just often not accurate / not calibrated correctly. I have one that is basically 5psi off, to get 35 in the tire you need 40 on the gauge. Knowing that, it's fine. From what I've read it's really common with them, but they're repeatable. The stick style ones have another variability in how they are used on top.
Doesn't matter much to me anymore since I picked up one of the little 20v Dewalt compressors. You just set the thing and it runs till it hits the setting, and so far it appears to be very accurate and consistent. Also works as a air pump for airbeds and such. Pretty happy with it. The Milwaukee ones are supposed to be good as well.
Doesn't matter much to me anymore since I picked up one of the little 20v Dewalt compressors. You just set the thing and it runs till it hits the setting, and so far it appears to be very accurate and consistent. Also works as a air pump for airbeds and such. Pretty happy with it. The Milwaukee ones are supposed to be good as well.
Now if you wanted, could have it checked against a know standard. For our welding gauges we had a test standard that was calibrated annual to a know standard by an outside firm. Production regulator gauges were checked against that gauge at a frequency set by QA.
Reminded of Marisa Tomei in My Cousin Vinny:
Last edited by JerryU; Nov 12, 2024 at 12:42 PM.
Le Mans Master
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From: Gilbert Arizona
Race Director
Joined: Sep 2016
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I think if one has two decent gauges from different brands, and they're within about 1/2 pd of each other, you can accept theiy're accurate enough. It's unlikely two totally different products are going to be off by the same amount.
I recall reading an article (in Road & Track, IIRC), probably 40 or more years ago, where the author visited a Schraeder factory that made pencil tire pressure gauges. He expected some high-tech machine for checking accuracy. Turned out they just compared them against each other, and if one varied by more than a small amount from the rest they just threw it out.
I would still test it against a separate gauge periodically, to make sure it stays accurate and doesn't drift.
Last edited by Red Mist Rulz; Nov 12, 2024 at 01:12 PM.
Melting Slicks
Joined: Sep 2020
Posts: 2,836
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From: Kelso, Wa
I have an old Michelin digital gauge, and Jaco digital. Both pretty close. I use an auto-stop pump and set it to 1/2 lb over. ..
By the way, I have set my (phone) calendar to remind me to do the air on the last Saturday of every month. .. .. The C8 is "up" for the winter so I won't check it again till the cover comes back off.
By the way, I have set my (phone) calendar to remind me to do the air on the last Saturday of every month. .. .. The C8 is "up" for the winter so I won't check it again till the cover comes back off.
Safety Car
Joined: Dec 2009
Posts: 4,303
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From: Oro Valley Arizona
Same Ol' Same Ol'
If you check your tires regularly and they are consistent one tire to another, you know you don't have an inflation issue. A leak from a nail etc. Michelin Man will tell you 10 degrees F can make a 1-2 psi delta so I don't get to OCD with the number. I'm looking for the anomaly. Once a month, I go all the way around and adjust to 30 psi cold. This works for me.
Advanced
Joined: Jun 2022
Posts: 82
Likes: 41
From my track days, I found "Longacre" tire pressure gauges the very best. In fact, it's reading is +/- 1 psi compared to the car reading (Corvette and Toyota Sienna). In contrast, the gauge on the portable tire inflators tend to read higher than actual.
Long story short, if you buy a trustworthy tire pressure gauge, then problem solved ! Cheers,
Michael
Long story short, if you buy a trustworthy tire pressure gauge, then problem solved ! Cheers,
Michael
Team Owner
Joined: Jun 2005
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From: Northern, VA
St. Jude Donor '15
"In honor of jpee"
Funny story (to me, anyway) about my Schrader gauges. Yes, I've had several...at one time. Plus a lot of other pencil gauges. A friend loaned me his digital gauge which wasn't expensive but it was pretty good.
Just for kicks (this was back in the early 2000's), I pulled out all my pencil tire gauges---almost all were the metal outside with a plastic indicator. I took the friend's digital and got a reading on all my tires (1 or 2 were off by a pound). With each of the pencil gauges I walked around the car and took the pressure they would register. That was, I think, seven circles of the car. Guess I could've done it all in one go-round, but I was energetic.
Only one of the el cheapo tire gauges were different than the digital one. And the one that was different was off by just under a pound---couldn't say if it was a half or more or less. I was pretty surprised. So was my friend.
Just for kicks (this was back in the early 2000's), I pulled out all my pencil tire gauges---almost all were the metal outside with a plastic indicator. I took the friend's digital and got a reading on all my tires (1 or 2 were off by a pound). With each of the pencil gauges I walked around the car and took the pressure they would register. That was, I think, seven circles of the car. Guess I could've done it all in one go-round, but I was energetic.
Only one of the el cheapo tire gauges were different than the digital one. And the one that was different was off by just under a pound---couldn't say if it was a half or more or less. I was pretty surprised. So was my friend.
Racer
Joined: May 2023
Posts: 304
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I learned a long time ago, buy a quality gauge and stick with it. Certainly occasionally check it against another known quality gauge. But never ever waste time having 2 or 3 gauges and checking with all of them, going to drive yourself crazy.
Learned from all my time at the racetrack, quality gauge plus knowledge of tires and what performance you are trying to achieve, looking closely at the tires you will know pretty quick if you are running the correct pressures or not.
Learned from all my time at the racetrack, quality gauge plus knowledge of tires and what performance you are trying to achieve, looking closely at the tires you will know pretty quick if you are running the correct pressures or not.