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Let's talk PSI

783 Views 43 Replies 12 Participants Last post by  rumrunner, 
skwormin
ok so the door sticker says 36 PSI.

I have a digital tire pressure gauge. When I measure to exactly 36 PSI (when 'cold', overnight in my garage ~50-60F) to TPMS / HUD shows around 33PSI, which warms up to 38 or so after driving.

I just got my car back from the dealer, and it looks like they decided to fill my tires up to ~39 PSI, from my digital gauge (when cold). But the HUD / TPMS says 36 when cold, warms up to ~42PSI when driving on the HUD.

Discuss.
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Mark_
Hummm. Mine is pretty much dead on, sensors vs digital gauge.

Is this a 2019+ thing ? Not sure I've heard of this before. Could you possibly try with a different gauge ?
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Fj4080
Mark_ said:
Hummm. Mine is pretty much dead on, sensors vs digital gauge.

Is this a 2019+ thing ? Not sure I've heard of this before. Could you possibly try with a different gauge ?
Click to expand...
My 2022 is right on with my digital gauge.
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skwormin
I only have this one digital gauge but I have a manual one I can try. Seems weird. Maybe my gauge is off.

This is the digital one I have... https://www.amazon.com/gp/product/B01J8DLGU2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
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AZJeeper
3 PSI difference between your gauge and EVIC is a lot. NHTSA says TMPS are accurate to "1 to 2 PSI". So either your digital gauge is off, or your TMPS is. I suspect your digital gauge is off by about 3 PSI!

I use the Tire Fill Alert feature and the tires measure within 1 PSI of my trusted gauges.
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skwormin
AZJeeper said:
3 PSI difference between your gauge and EVIC is a lot. NHTSA says TMPS are accurate to "1 to 2 PSI". So either your digital gauge is off, or your TMPS is. I suspect your digital gauge is off by about 3 PSI!

I use the Tire Fill Alert feature and the tires measure within 1 PSI of my trusted gauges.
Click to expand...
ya know, I have a bike floor pump, I can pump up my bike tires and compare it with the digital gauge there.
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AZJeeper
skwormin said:
This is the digital one I have... https://www.amazon.com/gp/product/B01J8DLGU2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Click to expand...
I have one of those. Mine is reasonably accurate. The 0.1 PSI part is misleading since it is accurate to 1% (according to AstroAI site). So 36.2 PSI is somewhere between 35.8 and 35.4 PSI. So your gauge should be close, but not 0.1 close. Mine is around that 1% as compared to my other trusted gauges. I've read reviews where that gauge has been off by 2-3 PSI.
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Mark_
Because the dealer pressures seem to match your sensors... I'd definitely try another gauge.
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rumrunner
I have trouble w/ our changing New England ambient temps. I'm happy if all 4 tires are within a lb or 2 of each other. when they all match, I feel like my day is complete
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Mark_
rumrunner said:
I have trouble w/ our changing New England ambient temps. I'm happy if all 4 tires are within a lb or 2 of each other. when they all match, I feel like my day is complete
Click to expand...
Don't come up here in the next few days. Forecast for tomorrow night : 25F. Friday low : 28. Sunday high : 85. Monday : 90...
A nightmare for PSI OCD 😭 :ROFLMAO::ROFLMAO:
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Flybynightcru
My analog dial gauge is also dead on with the TPMS. I also suspect your gauge is off...😎
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J
Yep try another gauge maybe a higher end mechanic shop style. Those off brand cheapy digital ones can be off by quite a bit. Ended up throwing a few away over the years because they were so inaccurate. Now I have a husky one from HD. Very accurate and reads high pressure trailer and truck tires which most of the cheap ones top out at 60-80 psi. Husky Digital Inflator Gauge 17889HOM - The Home Depot
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Mark_
jcool001985 said:
Yep try another gauge maybe a higher end mechanic shop style. Those off brand cheapy digital ones can be off by quite a bit. Ended up throwing a few away over the years because they were so inaccurate. Now I have a husky one from HD. Very accurate and reads high pressure trailer and truck tires which most of the cheap ones top out at 60-80 psi. Husky Digital Inflator Gauge 17889HOM - The Home Depot
Click to expand...
I have one of those too, but it's analog/needle style, and beat up to the point its origin can't get down to zero anymore so I'm always guessing. Seeing yours just now, went to Amazon and found just the dial part, for $8 (digital). We'll see :geek:
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sanghill
Cold PSI in your garage doesn't work. You drive outside, so if it is 50F in your garage and 20F outside your tires will not have the correct inflation pressure when driving outside. You have to check tire pressures before the sun shines of them and warms them up, usually unevenly.
I have serious doubts about the accuracy of a $12 gauge. Buy a dial gauge tire pressure gauge at NAPA or some other reputable auto parts store. TPMS accuracy is not reliable, refer to your Owner's Manual.
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rumrunner
fwiw

my current favorite gas station pump, is 1 lb off from my go-to gauge & Jeep's TPMS. meaning, if I want 35 I have to set it to 36
my go-to gauge & Jeep's TPMS match
my gauge was included w/ my deflators

Trailhead Automatic Tire Deflators - Home

Trailhead
www.trailheaddeflators.com

it's an interesting gauge. normally, with most other pencil style gauges, one can pull out the white gauge bar, but not this one. it only comes out when placed on a valve to show psi
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Lindy
Mark_ said:
Don't come up here in the next few days. Forecast for tomorrow night : 25F. Friday low : 28. Sunday high : 85. Monday : 90...
A nightmare for PSI OCD 😭 :ROFLMAO::ROFLMAO:
Click to expand...
Just when I think that I may have OCD, I will stumble across a thread like this and I'll feel much better about myself. :D
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AZJeeper
rumrunner said:
my gauge was included w/ my deflators

Trailhead Automatic Tire Deflators - Home

Trailhead
www.trailheaddeflators.com
Click to expand...
How do those deflators work for you? I had (past tense) another brand I used on my JK. I had mine set to 15 PSI, but would end up anywhere from 12 PSI to 18 PSI, different on every tire of course. Sometimes they wouldn't stop at the preset so I ended up underinflated (AKA "flat") if I didn't pay attention. I ditched them and now use a homemade two-tire Y-valve. I can open the valve and let massive pressure out, check the pressure from the valve manifold, and hook up my inflater for a two-tire fill. Much faster overall and since I do side-to-side at least the tires on the same axle are exactly the same pressure. I sometimes like different front-to-back pressures by a few lbs since the front is significantly heavier than the back (slightly higher PSI front), or if I'm towing (slightly higher PSI rear). I have 37's so it's really a different ballgame than the Cherokee. But I have used it as a deflator on the KL from time to time too.

The included gauge seemed accurate - until it broke!
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S
I think mine is pretty accurate. Depending on temperature I vary between 30 and 40 psi year round.
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rumrunner
Lindy said:
Just when I think that I may have OCD, I will stumble across a thread like this and I'll feel much better about myself. :D
Click to expand...
be thankful you're not on a cycling forum discussing how to clean your chain
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rumrunner
AZJeeper said:
How do those deflators work for you? I had (past tense) another brand I used on my JK. I had mine set to 15 PSI, but would end up anywhere from 12 PSI to 18 PSI, different on every tire of course. Sometimes they wouldn't stop at the preset so I ended up underinflated (AKA "flat") if I didn't pay attention. I ditched them and now use a homemade two-tire Y-valve. I can open the valve and let massive pressure out, check the pressure from the valve manifold, and hook up my inflater for a two-tire fill. Much faster overall and since I do side-to-side at least the tires on the same axle are exactly the same pressure. I sometimes like different front-to-back pressures by a few lbs since the front is significantly heavier than the back (slightly higher PSI front), or if I'm towing (slightly higher PSI rear). I have 37's so it's really a different ballgame than the Cherokee. But I have used it as a deflator on the KL from time to time too.

The included gauge seemed accurate - until it broke!
Click to expand...
wow, impressive system you have for the fatties

mine work very well

I initially got a diff. set: LXPVSA Coyote Automatic Tire Deflators, 4 to 56 PSI, 4 Pack
www.amazon.com

Amazon.com: LXPVSA Coyote Automatic Tire Deflators, 4 to 56 PSI, 4 Pack : Automotive

Buy LXPVSA Coyote Automatic Tire Deflators, 4 to 56 PSI, 4 Pack: Tire Repair Tools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com

which required me to set the psi on each unit, then lock in the setting w/ a knurled ring, which always seemed to move. I got close but I was inconsistent, plus it was difficult to get them exact. these units from "Trailhead" are very accurate & very reliable. someone recommended them to me at the beach air station & I'm so glad I struck up a convo when I saw him using his

I think I just recycled the Coyotes, but I might have them in basement somewhere ...

a favorite beach requires 11psi, these come preset at 12. close enough. I recently misjudged a parking space at the beach, a berm crest, too close to the water, hehe, & I wanted to go down to 10, to back up. whipped out my gauge & they were all 12 & I brought them all down to 10 for the rest of the day. easy peasy

another beach requires 15 psi. it's flatter & less challenging & the ruts are deeper. so what I do is go around, attach all 4, then when I think I'm getting close, visually, I take them all off & fine tune down to 15. but if they were all 12 that would be fine

at my knees' age, actually 15-20 years ago, I got myself a little folding stool for the deflating using a key or whatever. now I just go around, put all 4 on & wait for them to stop whistling / hissing, then take them off. they are so reliable, I don't even double check the pressure w/ the gauge. OCD be dammed ;-)

some ppl say they screw them on then go drive on the beach & take them off later. but why? just why?

they come in diff. colors
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