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The compressor stays in the car. It’s the size of a book. Remember those. I’m not diy but I have a compressor in each car.
Oh you mean the electric emergency compressors. Yeah that's true. I swear most of the ones I've owned can barely handle though. For topping off on a bi weekly basis though i suppose it's fine for that.

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the 50 psi max is for COLD inflation, tire mfg have taken into account temp rise as the tire heats up so even if it is above 50psi hot nothing to worry about as long as cold is near where the car mfg recomends. Don't worry if hot temp psi rises 5-10 psi.

Boyles Law PV=rT, T= degrees kelvin (room temp is about 275 Kelvin) P= pressure. V= volume. Since tire volume is almost constant with pressure (for reasonable changes in pressure in a car tire) , P is pretty linearly related to temperature. so, "back of the envelope" calculation says a 27K temp change (about 45F) should cause about a 10% pressure change, or for "typical" car tires around 1psi for each 10-15F temp change. Or 35psi at "room temp" will certainly drop it below 30psi by -20F. And that internal tire temp can be 40F or more above outside when the tire is hot, a noticeable pressure increase after a drive on a hot day.
Are you saying temp inside the tire can be 40 degrees higher then the outside temperature
 

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I purchased a Ryobi P737 18-volt portable air compressor back in 2018 (Amazon return, $23, no battery). I had two batteries from my Ryobi drill set I can use with the air compressor. Got it mainly for my bikes; but, it work perfectly for adjusting my tire PSI when needed. I sometimes toss in the back on long road trip just in case.
 

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These are what I keep in the back my CX-5 and MDX. Originally purchased to have air while overlanding (along with a portable jump starter) but decided I'd never like to be without air regardless of where I'm at so they permanently reside in the under-floor storage trays. They certainly aren't as quick as a gas station pump, increasing pressure by about 3psi/minute, but it's better than nothing.
 
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Are you saying temp inside the tire can be 40 degrees higher then the outside temperature
depending on the speed and load, a 20-40F rise in INTERNAL tire temp is not unexpected. My trailer TPMS monitors internal tire temp and on a 70F day after an hour or so of driving internal tire air temp if often in the 95-100F range on the shaded side of the trailer and hotter on the sun side. Internal temp rises from friction along with the black tire heat rise from the sun. In fact just sitting in the sun that side of the trailer internal tire temp often has a 20F or more rise by afternoon.

That's why the best way to check tire temp is with the tire cold and not exposed to sunlight.
 

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I purchased a Ryobi P737 18-volt portable air compressor back in 2018 (Amazon return, $23, no battery). I had two batteries from my Ryobi drill set I can use with the air compressor. Got it mainly for my bikes; but, it work perfectly for adjusting my tire PSI when needed. I sometimes toss in the back on long road trip just in case.
depending on the speed and load, a 20-40F rise in INTERNAL tire temp is not unexpected. My trailer TPMS monitors internal tire temp and on a 70F day after an hour or so of driving internal tire air temp if often in the 95-100F range on the shaded side of the trailer and hotter on the sun side. Internal temp rises from friction along with the black tire heat rise from the sun. In fact just sitting in the sun that side of the trailer internal tire temp often has a 20F or more rise by afternoon.

That's why the best way to check tire temp is with the tire cold and not exposed to sunlight.
wow I can’t say i learn something everyday but I did today Thanks
 

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but decided I'd never like to be without air regardless of where I'm at so they permanently reside in the under-floor storage trays
You're smart to do so. I always carry an inflator in that location as well. I think I may have started doing it long ago when I did a lot of 4 wheeling but they're inexpensive, don't take up much room, and could save the day if running into an issue.

A friend had a flat tire (not MDX) and went to change it but then found out the spare, which was under the floor in the trunk, was super low on pressure since he'd never checked the tire pressure on the spare before and it was now years later. This caused what would've been a fairly quick and easy problem to be much more of a hassle (I think I rescued them). I suggested he get an inflator to leave in the car (and also to check the pressure in the spare every now and then) and he got one right away.
 

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A friend had a flat tire (not MDX) and went to change it but then found out the spare, which was under the floor in the trunk, was super low on pressure since he'd never checked the tire pressure on the spare before and it was now years later. This caused what would've been a fairly quick and easy problem to be much more of a hassle (I think I rescued them).
I hadn't even considered that situation! Thanks for the reminder. I know I haven't checked the spare since I installed my trailer hitch last year
 

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as an update to tire temperatures. Today I had my trailer parked in the driveway facing N. In the afternoon, one side in the shade, one side in the sun. Ambient temps were about 75 degrees. about 3pm I checked the tires using my TPMS. shaded tire internal temperature 77 on both tires. Tires on the sunny side all afternoon internal temp was 95F and 93F on the two tires. about a 15 degree rise just by sun or shade. 15 degrees will be around a 1-1.5psi tire pressure change. And remember once moving for any length of time internal temps will rise even more due to friction etc. That's why tire mfg and car mfg say check tire pressure cold. It's a good reference point.
 

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Tires on the sunny side
That's a good point. Whenever I check my tires for the pressure 'cold' I always do it earlier in the morning while the tires are still in the shade. The sun can heat up the tires a lot and the pressure can be much higher on the sunny side of the car.
 

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After picking up my 2019 MDX up from the dealership for a regular service, I noticed tires were set to about 35psi, which I understand is the recommended tire pressure when the car is cold.

It's summer here and the tires get up to about 40 psi while driving on the freeway. I know the numbers increase during normal usage, but at number does it become dangerous and at risk of blowing out?
Yep, set them while cold and don’t worry about how high when hot.
 
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