PSA: Top off your tires

[jebmke]

Cold weather has settled into the mid-Atlantic. This is the time I normally top off my tires even if I have been doing it every month or so normally. Cold weather knocks back the pressure.

This time I checked the spare -- something I often forget. It was way down.

[whodidntante]

Better yet, switch to winter tires. Sorry, had to.

[jebmke]

Better yet, switch to winter tires. Sorry, had to.

Not around here; it rarely snows. and if it does, I just flip on 4WD in order to go out to the mailbox.

[vfinx]

And a bicycle pump works great for top offs. About 10 strokes per psi give or take, depending on tire size and type of pump. No need for a noisy compressor.

[heartwood]

Has anyone tried an Airmoto? https://www.amazon.com/Airmoto-Tire-Inf ... r=8-1&th=1


I play solitaire and other games online and get unending ads to buy one. It looks good, if a bit pricey.

Their ads show gas stations with "out of order" taped across the air pumps or plugged con inserts. Happened to me a few months ago after I put my $3 in quarters into the slot: broken air hose.

Does it work?

[jebmke]

We use a similar device made by Black and Decker. I've checked the results and it seems to work fine. I check my tires every month or so.

[arcticpineapplecorp.]

thanks. my 2023 Toyota Corolla Hatchback told me air pressure was low in right side tires (front and back) two weeks ago. Toyota dealership fills up for free!

[Wabbit]

Has anyone tried an Airmoto? https://www.amazon.com/Airmoto-Tire-Inf ... r=8-1&th=1


I play solitaire and other games online and get unending ads to buy one. It looks good, if a bit pricey.

I got this tire inflator, a bit cheaper, and it has been working well enough for my occasional use for the last couple of years. No battery though, you need to plug it in (and have the car's electrical turned on):

https://www.amazon.com/gp/product/B073VB41W3/

Of course that's only me, not enough to get at overall reliability between brands. Anyway, I also have experienced gas stations with their air compressors "broken" for more than a year, it was getting tough to find one which inspired me to get my own portable.

[mhalley]

Just a warning, I watched a video recently where they tore down battery operated tire inflaters and the majority were lying about the battery size. It would say 25000h but it would only have 500 etc. They would struggle to inflate one tire before needing recharged. So do a lot of research or get one that plugs into the car.

[livesoft]

I keep one of those combo battery jumper, air pump, USB output, 120VAC output in my car. I use it routinely without issues. Since my car has TPMS on all 4 tires and I can enter the desired pressure on the air pump it is rather trivial to keep tires at spec.

And I have seen poor reviews of the combo device I have, but it is still going strong 5 years later.

[jebmke]

I keep one of those combo battery jumper, air pump, USB output, 120VAC output in my car. I use it routinely without issues. Since my car has TPMS on all 4 tires and I can enter the desired pressure on the air pump it is rather trivial to keep tires at spec.

And I have seen poor reviews of the combo device I have, but it is still going strong 5 years later.

did you get the defibrillator attachment? Our local hospital is not strong on cardio urgent care and nearest one that is is an hour away (on a good day, 3-4 hours on a bad day).

[livesoft]

did you get the defibrillator attachment? Our local hospital is not strong on cardio urgent care and nearest one that is is an hour away (on a good day, 3-4 hours on a bad day).

No, but my son has an AED in his vehicle as part of his job. EMT is about 3 minutes away and has been to the house a couple of times due to MIL issues.

[iamlucky13]

Has anyone tried an Airmoto? https://www.amazon.com/Airmoto-Tire-Inf ... r=8-1&th=1


I play solitaire and other games online and get unending ads to buy one. It looks good, if a bit pricey.

Their ads show gas stations with "out of order" taped across the air pumps or plugged con inserts. Happened to me a few months ago after I put my $3 in quarters into the slot: broken air hose.

Does it work?

I do not have one, but it looks very small, and I can say that when it comes to pumping fluids, there is no replacement for displacement...not even a stylish plastic cover.

Nothing prevents a quality-minded manufacturer from making a small inflator that works, but physics is going to limit how fast it can work and how much battery capacity it has. It is hard to know if this is a quality-minded manufacturer. The current Amazon paradigm where unknown companies send out hundreds of free units to solicited reviewers in exchange for positive reviews makes it difficult to guess what it means when unheard of companies that are largely untraceable seem to have immense popularity out of nowhere.

With thay said, if it is of reasonable quality, I would expect it to be able to slowly top off a tire, but not fill one from empty. That seems consistent with what is shown here:

https://youtu.be/rhuWBG8MnFU?si=WpqvdhGhTrULSvfc

I didn't watch the full review, but skipped to the summary at 9:25. It sounds like the larger Fanttik took nearly 15 minutes to half fill an admittedly large tire, while the Airmoto overheated or ran out of battery after 28 minutes, still not having finished.

I checked this review in part because I saw the Fanttik at Costco recently, I think for $50, so it seemed like a good point of comparison. Costco actually chooses the products they sell, and their procurement teams' performance is reviewed based on their popularity and customer satisfaction. Based on the Youtube review, the Fanttik seems like a tolerable automotive tool, and the Airmoto seems like a bike pump.

[Jack FFR1846]

I found one tire very low and it had the indicator for low pressure on. I looked and saw no obvious nail/screw. Pulled the tire and filled it to 45 and slowly rolled it around. It was wet, so that made it easier. There it is. A hole that looked like a small nail went in and came back out. No nail, just the hole. I did the DIY plug and driven 100 miles and hasn't lost any air. I will be swapping to snows soon but I'm retired. If it starts snowing at 3 in the afternoon, I'm not stuck at work an hour away or anything. My son just changed his today. His high performance summer tires say not to drive them below 40 degrees and if they are subjected to temperatures under 40 to bring them where they are over 40 for at least 24 hours. I know my Lotus manual said right in it to never drive the car on the OEM tires when the temperature is under 40. That's sort of the step function temperature. Snow/winter tires have compounds that work far better below 40 than high performance summer tires. I don't know about no-season tires as I've never bought them as I don't live in Florida.

[kevinf]

Better yet, switch to winter tires. Sorry, had to.

And if you have winter tires on, lower pressure can help with grip. Under is better than over for snows.

[yankees60]

Has anyone tried an Airmoto? https://www.amazon.com/Airmoto-Tire-Inf ... r=8-1&th=1


I play solitaire and other games online and get unending ads to buy one. It looks good, if a bit pricey.

Their ads show gas stations with "out of order" taped across the air pumps or plugged con inserts. Happened to me a few months ago after I put my $3 in quarters into the slot: broken air hose.

Does it work?

If I did not have one I'd buy it now based upon you bringing it to my attention. I get swayed by the combination of 4+ stars and this many ratings: 13,824 ratings.

This is what I bought last January based upon someone in the forum recommending it. I see that it now has 25,000+ rating. I was extremely impressed with it the only time I've used it. Overdue for using it again.

https://www.amazon.com/dp/B07CTGM2LD/?r ... l_huc_item
AVID POWER Tire Inflator Portable Air Compressor, 20V Cordless Car Tire Pump, Rechargeable Battery Powered Air Compressor w/12V DC Adapter, Digital Pressure Gauge

[Kenkat]

I highly recommend the Ryobi 18v Air Inflator if you have the Ryobi line of rechargeable tools:

https://www.ryobitools.com/products/details/33287178452

Just used it yesterday when my tire inflation warning came on.

[yankees60]

I highly recommend the Ryobi 18v Air Inflator if you have the Ryobi line of rechargeable tools:

https://www.ryobitools.com/products/details/33287178452

Just used it yesterday when my tire inflation warning came on.

They seem to be evasive on its price?

[sport]

The Costco store near me has complimentary air pumps in the parking lot. They use nitrogen to fill your tires.

[YeahBuddy]

No need to top off tires, most cars alert you to low PSI, or you can check with a tire gauge, and tire pumps you can plug into your car's charging port are very affordable. For the past few days, my car reads low psi, just for that warning light to go away because your tires heat up as you drive, pushing the psi into the normal range within 10 min of driving.

Also, Costco will purge and refill with pure nitrogen for free if you buy your tires there and nitrogen is more stable and less likely to have such fluctuations. I plan to go this week.

[yankees60]

No need to top off tires, most cars alert you to low PSI, or you can check with a tire gauge, and tire pumps you can plug into your car's charging port are very affordable. For the past few days, my car reads low psi, just for that warning light to go away because your tires heat up as you drive, pushing the psi into the normal range within 10 min of driving.

Also, Costco will purge and refill with pure nitrogen for free if you buy your tires there and nitrogen is more stable and less likely to have such fluctuations. I plan to go this week.

About what time range did cars start giving these alerts? I have a 2004 Honda Accord, which was before MP3 players so it does not even have an input for the sound system ...... let alone letting me know what is going on with the tires.

[cmr79]

Most of my vehicles have tire pressure alerts at much lower pressures than I would tolerate, like 25 when spec is 30-35. I usually fill tires to the higher end of the pressure range, so if the TPMS alert comes on, it probably means I have a leak.

[cmr79]

The Costco store near me has complimentary air pumps in the parking lot. They use nitrogen to fill your tires.

My home pump uses a blend of 79% nitrogen

[michaelingp]

About what time range did cars start giving these alerts? I have a 2004 Honda Accord, which was before MP3 players so it does not even have an input for the sound system ...... let alone letting me know what is going on with the tires.

They were mandatory starting in 2008, so probably not in the majority of cars of the notoriously thrifty Bogleheads.

[YeahBuddy]

No need to top off tires, most cars alert you to low PSI, or you can check with a tire gauge, and tire pumps you can plug into your car's charging port are very affordable. For the past few days, my car reads low psi, just for that warning light to go away because your tires heat up as you drive, pushing the psi into the normal range within 10 min of driving.

Also, Costco will purge and refill with pure nitrogen for free if you buy your tires there and nitrogen is more stable and less likely to have such fluctuations. I plan to go this week.

About what time range did cars start giving these alerts? I have a 2004 Honda Accord, which was before MP3 players so it does not even have an input for the sound system ...... let alone letting me know what is going on with the tires.

Right after the invention of horse and buggy!
Just make it a habit to regularly check your tire pressure with a gauge, and fill with something like this for ~ $20.... (it's better than just topping off your tires once in a while)

https://www.amazon.com/AstroAI-Portable ... 198&sr=8-2

[YeahBuddy]

The Costco store near me has complimentary air pumps in the parking lot. They use nitrogen to fill your tires.

My home pump uses a blend of 79% nitrogen

78%*
78.08% to be more accurate.

[Kenkat]

I highly recommend the Ryobi 18v Air Inflator if you have the Ryobi line of rechargeable tools:

https://www.ryobitools.com/products/details/33287178452

Just used it yesterday when my tire inflation warning came on.

They seem to be evasive on its price?

Hmmm. It looks like they have recently updated it to a different form factor:

https://www.homedepot.com/p/RYOBI-ONE-1 ... /327406129

I think I like the one I have.

[criticalmass]

The Costco store near me has complimentary air pumps in the parking lot. They use nitrogen to fill your tires.

I think all Costco stores with tire sales have nitrogen pumps. I usually find it easier to fill at home then goof around at Costco though.

My bicycle pump is most convenient anywhere, and supplies 78% nitrogen with a 0.1 PSI increase with each stroke. I keep my tires about 2 psi above the car placard recommended pressure, unless there is snow on the ground--which is rare. Then a little less pressure improves traction and braking.

Always measure your tire pressure when cold (e.g. not baking in the sun and hasn't been on the road for at least 30-50 minutes). Otherwise you would under fill your tires.

Last summer I stopped at a Costco in a rental car on the other side of the country. While there, decided to check pressure before a road trip into the mountains, and 2 tires were 10 PSI low! Got that fixed quickly.

[Nestegg_User]

I highly recommend the Ryobi 18v Air Inflator if you have the Ryobi line of rechargeable tools:

https://www.ryobitools.com/products/details/33287178452

Just used it yesterday when my tire inflation warning came on.

They seem to be evasive on its price?

They were on sale at Home Depot for $30 last couple of days (Black Friday deal)

I have one that I've had for a little bit. Works well for car tires (but the pressure has to be "upped" a little (measurement slightly lower at tire that at device manifold); I don't know if it would work for truck tires (80 psi) even though the device says it can go to 100 psi.

...and as for snows... already had them on before the 2 foot (plus) hit the area a couple of weeks ago (and they are Nokians) {I've got my chains ready too, although I doubt I'll need them}

[Nestegg_User]

The Costco store near me has complimentary air pumps in the parking lot. They use nitrogen to fill your tires.

My home pump uses a blend of 79% nitrogen

mine too
mine even has some argon in it

[JediMisty]

The Costco store near me has complimentary air pumps in the parking lot. They use nitrogen to fill your tires.

My home pump uses a blend of 79% nitrogen

I like what you did there!

[blortchplop]

Just topped them up. Thanks. They were several PSI low. Now they're up by 1.

I have a portable tire inflator that plugs into the 12V cigarette lighter plug in the car, pretty sure it's this model: https://www.jbtools.com/bell-automotive ... -inflator/. Have had the thing for years, and it still works well.

I overfill a little and then check with a digital pressure gauge and deflate to the desired pressure. Went out of my way to get a pressure gauge that had some kind of calibration.

[Grt2bOutdoors]

Went through this 2 weeks ago, one day fine, first cold snap and that pesky light turned on. I should check my tire pressure more often.

[Makefile]

About what time range did cars start giving these alerts? I have a 2004 Honda Accord, which was before MP3 players so it does not even have an input for the sound system ...... let alone letting me know what is going on with the tires.

They were mandatory starting in 2008, so probably not in the majority of cars of the notoriously thrifty Bogleheads.

I believe it's an outgrowth of the Ford Explorer Firestone scandal, actually.

[seawolf21]

Has anyone tried an Airmoto? https://www.amazon.com/Airmoto-Tire-Inf ... r=8-1&th=1


I play solitaire and other games online and get unending ads to buy one. It looks good, if a bit pricey.

Their ads show gas stations with "out of order" taped across the air pumps or plugged con inserts. Happened to me a few months ago after I put my $3 in quarters into the slot: broken air hose.

Does it work?

If you are are going to spend that amount of money on the Airmoto, I recommend

RIDGID 18V Cordless Portable Inflator Kit with 2.0 Ah Battery and Charger

https://www.homedepot.com/p/RIDGID-18V- ... /314026557

RIDGID offers lifetime warranty on equipement and battery. The inflator also includes a 12V adapter.

[kevinf]

Use caution with 12v accessory power inflators, they can blow your 12v ACC fuse if you operate them continuously. Give it a 1 minute break every 3 mins or so.

[RickBoglehead]

No need to top off tires, most cars alert you to low PSI, or you can check with a tire gauge, and tire pumps you can plug into your car's charging port are very affordable. For the past few days, my car reads low psi, just for that warning light to go away because your tires heat up as you drive, pushing the psi into the normal range within 10 min of driving.

Also, Costco will purge and refill with pure nitrogen for free if you buy your tires there and nitrogen is more stable and less likely to have such fluctuations. I plan to go this week.

Bad info.

Tires should be checked cold, and tpms is not a replacement for a tire gauge.

[criticalmass]

No need to top off tires, most cars alert you to low PSI, or you can check with a tire gauge, and tire pumps you can plug into your car's charging port are very affordable. For the past few days, my car reads low psi, just for that warning light to go away because your tires heat up as you drive, pushing the psi into the normal range within 10 min of driving.

TPMS is a last result to warn drivers before low conditions that can lead to tire failure. The system in the USA is a product of multiple tire failures resulting from under inflation. Remember the Ford Explorer tire issues/crashes many years ago?
In other words don't rely on TPMS warnings, unless your TPMS is providing accurate measurements, not just a bad news warning. Be proactive and either check your own tires or have someone do it regularly, not just when weather changes because punctures and slow leaks can happen any time.

Also, Costco will purge and refill with pure nitrogen for free if you buy your tires there and nitrogen is more stable and less likely to have such fluctuations. I plan to go this week.

Costco does fill with nitrogen. However you can fill with almost 80% Nitrogen with any tire pump. And Boyle's Law applies to all air, not just nitrogen.

[lazydavid]

Has anyone tried an Airmoto? https://www.amazon.com/Airmoto-Tire-Inf ... r=8-1&th=1


I play solitaire and other games online and get unending ads to buy one. It looks good, if a bit pricey.

Their ads show gas stations with "out of order" taped across the air pumps or plugged con inserts. Happened to me a few months ago after I put my $3 in quarters into the slot: broken air hose.

Does it work?

I have the Fanttik ones in every car, and also gave one to my parents. They work very well.

[YeahBuddy]

Costco does fill with nitrogen. However you can fill with almost 80% Nitrogen with any tire pump. And Boyle's Law applies to all air, not just nitrogen.

I'm fully aware. Air is actually 78.08% nitrogen. I've seen arguments, and experiments, on both sides. Even if it's a sales gimmick, it won't cost me a penny to have Costco fill them with nitrogen and make some of my own anecdotes from the experience

But what is not a gimmick or much debate is properly measuring your tire pressure on a regular basis and filling to proper PSI, vs randomly topping off at some point during the year, as OP suggests.

[andypanda]

You can buy a serious 12v compressor from VIAIR for much less than $100.

"VIAIR 88P - 00088 Tire Inflator Portable On/Offroad Air Compressor for Car, Truck, SUV & RV | 12V Heavy Duty Pump 120 PSI, Alligator Clip, Twist Chuck"

$76.75

www.amazon.com/Viair-00088-88P-Portable ... 39814&th=1

I use a $250 VIAIR model because I need to air up a 4Ruuner from 16 to 32 regularly and anything that's fast and high capacity requires connecting directly to the battery with the engine running. We've been driving on the beaches of the Cape Hatteras National Seashore for 2 weeks at 17 psi, so I will air up tomorrow before we leave. It doesn't hurt the tires to drive on Rt.12 at 45 or 50 for a few miles several times a day for a couple of weeks. I've been doing this since 1986.

"VIAIR 400P/40045 Automatic Portable Compressor, Tire Inflator Kit, Air Compressor for Truck, Jeep, SUV, and Car Tires, Portable Air Pump Kit, Car Accessories, 33% Duty Cycle, 150 PSI/2.30 CFM"

P.S. - Sure, the tackle shop has a free air pump, but you never know when it will break, or the line will be long, or the power to the island goes out. It's easier just to own a good pump.

[BolderBoy]

You can buy a serious 12v compressor from VIAIR for much less than $100.

"VIAIR 88P - 00088 Tire Inflator Portable On/Offroad Air Compressor for Car, Truck, SUV & RV | 12V Heavy Duty Pump 120 PSI, Alligator Clip, Twist Chuck"

$76.75

www.amazon.com/Viair-00088-88P-Portable ... 39814&th=1

This is the brand (different model) that I've had in my autos since 2012. Works fine (had to help out other people on occasion).

Highly recommended to carry an inflator in your auto, "for that day..."

[greenspam]

“Costco does fill with nitrogen. However you can fill with almost 80% Nitrogen with any tire pump. And Boyle's Law applies to all air, not just nitrogen.”

We are talking needing a pump to increase n (# of gas molecules) in the tire, due to the reduction in T (temperature) as cold weather sets in. This is explained by the Ideal Gas Law, (not Boyle’s Law, which says PV= constant at constant temps):

Boyle’s Law and the Ideal Gas Law are both principles in physics that describe the behavior of gases, but they differ in scope and application:

Boyle’s Law

   •   Definition: Boyle’s Law states that for a fixed amount of gas at constant temperature, the pressure () of the gas is inversely proportional to its volume ().

   •   Key Variables: Pressure (), Volume (), and constant Temperature.
   •   Focus: Describes the relationship between pressure and volume only.
   •   Conditions: Applies when the temperature and the number of gas molecules remain constant.
   •   Scope: A specific, simpler gas law dealing with a part of the overall gas behavior.

Ideal Gas Law

   •   Definition: The Ideal Gas Law combines several gas laws (including Boyle’s, Charles’s, and Avogadro’s laws) into one equation:

Where:
      •   : Pressure
      •   : Volume
      •   : Number of moles of gas
      •   : Universal gas constant
      •   : Temperature (in Kelvin)
   •   Key Variables: Pressure (), Volume (), Temperature (), and the amount of gas ().
   •   Focus: Provides a comprehensive description of gas behavior under various conditions.
   •   Conditions: Assumes the gas behaves ideally (no intermolecular forces, and gas molecules occupy negligible volume).
   •   Scope: A broader law that encompasses the behavior of ideal gases under all conditions.

Key Differences

Aspect Boyle’s Law Ideal Gas Law
Scope Relationship between  and  only Relationship between , , , and 
Variables ,  (at constant ) , , , 
Equation  
Application Simple cases (constant ) Comprehensive gas behavior

Boyle’s Law is a subset of the Ideal Gas Law, which applies specifically when temperature and the amount of gas are constant.

Just wanted to clarify as folks here are getting into the nitrogen concentration in air to the hundredth place

[greenspam]

PV=nRT. When I copied/ pasted the formula didn’t come thru !!!

[iamlucky13]

If you have an easy source of nitrogen to fill your tires with, feel free to use it. I'm not aware of any downsides to using it except availability (and circumstantially, price), and there are a few, normally very minor benefits I'll discuss below.

But I would not delay topping off your tires until you have access to nitrogen.

I personally don't bother, as the convenience of filling at home is more important to me.

...and nitrogen is more stable and less likely to have such fluctuations. I plan to go this week.

Nitrogen is more chemically stable, but since we're talking about passenger cars, not a 747 performing an emergency landing, we're not talking about chemical reactions. In terms of gas behavior, nitrogen is not inherently less prone to pressure fluctuations.

The chemical stability can be of interest at extremely high temperatures, as it reduces the risk of any flammable vapors igniting that might be present. This is of particular interest for aircraft tires, which can heat up very rapidly during landing, especially under unusually heavy braking, and that in severe situations can outright catch fire.

In both aircraft and in racing, it is also desirable to avoid having moisture inside the tire, as a portion of it may alternately evaporate and condense again as the tire heats and cools, increasing somewhat the change in pressure with temperature - when a phase change is occurring, we no longer have an ideal gas. The production of nitrogen by distillation removes moisture (so does using stored compressed air, to a lesser degree), effectively eliminating this factor. However, if you're heating passenger car tires up enough to boil water, there are bigger safety concerns that should be addressed as a far higher priority than filling the tires with nitrogen.

Hypothetically, the lack of moisture in nitrogen would also help reduce corrosion, but I have not observed corrosion to be an actual issue even with steel rims, much less with the aluminum rims that have become increasingly the norm.

It is claimed that nitrogen (N2) is "larger" than oxygen (O2), so nitrogen-filled tires lose pressure more slowly. This sounds a bit contradictory, since O2 has the higher molecular mass, but it is documented in academic research that N2 has a very slightly larger "kinetic diameter" that affects its diffusion through relatively non-permeable membranes. Consumer Reports did a simple, medium-sized test (31 different models of tires, one sample of each filled with nitrogen and one with air), which over 12 months showed a slight advantage for nitrogen (2.2 psi loss) vs air (3.5 psi loss).

For more rapid losses, such as due to an embedded nail, a bad valve stem, or a malformed bead, where there is an actual leak path rather than loss by permeation, "kinetic diameter" is going to be much less of a differentiating factor. Arguably, 12 months is longer than one should go without checking tire pressure anyways. The NHTSA says to do so monthly, which would make the difference in loss rates effectively irrelevant.

[talzara]

Most of my vehicles have tire pressure alerts at much lower pressures than I would tolerate, like 25 when spec is 30-35. I usually fill tires to the higher end of the pressure range, so if the TPMS alert comes on, it probably means I have a leak.

Most cars with direct TPMS are programmed to display a low tire pressure warning at about 75% of the specified tire pressure.

This number was selected for safety, not efficiency. Above 75%, the tire is unlikely to blow out. However, lower tire pressure will reduce your fuel economy even if the tire is safe to drive on.

[jayjayc]

I use nitrogen but only b/c that's what the Costco pumps happen to use. Their pumps are the best. Ultra fast, free and convenient. Many of the gas station pumps here require you to go inside and ask them to turn it on. I did buy my own pump which is handy, but the Costco ones are kinda fun to use.

[cheesepep]

And a bicycle pump works great for top offs. About 10 strokes per psi give or take, depending on tire size and type of pump. No need for a noisy compressor.

That is what I do!

[chuckwalla]

I don't think Costco inflators they have out in parking lots use nitrogen.

[sport]

I don't think Costco inflators they have out in parking lots use nitrogen.

They do in my area. I know that because one time they were out of nitrogen and they put up a sign that only air was available if you used the inflator.