…is checking the air pressure in the spare tire.
No need to ask how I know this…
A lot of people don’t check the air in their on-duty tires often enough, let alone the spare.
The spare on my car adds an extra level of pain in the ass because it’s stored face down under the trunk floor. So you not only have to open the trunk and raise the floor, but you actually have to unscrew the storage clamp, flip the tire over, check/fill it, then wrestle it back into place again.
I’ll admit to only doing this twice a year, when I switch between summer/winter tires.
I’d say the most neglected DIY maintenance is washing the car, which people actually brag about, but checking tire pressure is up there.
Or the half-assed check. Open the hatch, lift the floor, push on tire with your hand, “Seems good enough”
Two weeks later put it on your car and watch the rim settle to one mm off the road.
You know, I once found myself stranded on the interstate for that very reason… and I still don’t do it.
Well, my new car doesn’t have a spare. It has a pump and a can of fix a flat. At least I don’t have to worry about not checking the spare, anyway!
That’s why I carry a portable air compressor that runs off the 12V. I splurged and got the one for $30 where you can set a pressure and it will automatically shut off. I use 36 psi. Now I top off my tires at least once a month.
After a debacle in holiday gifts one year work gave us a catalog to choose our own gift the following year. I opted for the cig lighter powered tire inflater. I was at home & checked my tire, it was a bit low so I pulled out & opened my “wonderful” new gift & attached it to the tire on my Integra (hardly the heaviest car). The pump was such a PoS that the chuck depressing the pin in the Schrader valve actually caused more air to come out of the tire than to go into it resulting in even lower pressure than when I started. :smack:
What kind do you have that really works?
I drive a 30 year old two seater sports car. The spare is stowed uninflated to save space. Also stowed with it is a big ass can of tire inflator. I presume this set up works, but really don’t want to ever have to test it.
Yeah? What if your car gets struck by lightening which fries the battery and causes you to swerve and hit a big pothole which dislodges the valve stem cover and wedges a rock in the Schrader valve, depressing the pin and letting the air out of the tire? What then?
That’s what the Segway, Rollerblades and skis are for.
While you’re at it, why not ask “Where can I get a goose that lays a golden egg?” 
And while you’re at it, make sure you have the entire tire-change set still in the trunk.
Did you know that on many late-model vehicles you can’t even jack the car up without the tire iron? Let alone remove the tire, or replace it with the spare. :mad:
Also, did you know that road service is a good investment, for those times you can’t change the tire yourself for stupid and unexpected reasons?
[QUOTE=Doctor Jackson]
I drive a 30 year old two seater sports car. The spare is stowed uninflated to save space. Also stowed with it is a big ass can of tire inflator. I presume this set up works, but really don’t want to ever have to test it.
[/QUOTE]
What kind of tire changes shape enough to be worth that hassle? And what can of “fix a flat” has enough gusto to seat a bead?
I knew they existed (when I was a kid a neighbor had a '79 Trans Am with one of these) but I had never seen one inflated. Your question prompted me to go looking for videos.
Can’t speak for Saint Cad, but I have a Slime pump for my motorcycle. I’ve used it, and it works well. The motorcycle one is pretty compact and probably has too low a flow rate to inflate a car tire in a reasonable time, but their 40022 says it will inflate a “standard mid-size car tire” in 6 minutes.
I have one around here somewhere that I got at Big Lots of all places. Works great. Takes a bit, it’s a little puny, but it does work. Unfortunately it’s in the garage somewhere where it will not help if I need it.
Actually I would say checking ANY tire pressure with checking the oil being a close second. Not from personal knowledge, of course - I’m religious with both and several other points worthy of checking. But a close cousin works for a towing service. 
The issue with those on the temporary spares/compact spares is that they only go to like 30 or 40psi and the spares take 60. Now I admit that 30 beats flat but a AAA card will beat both on a rainy night.
Most hire car companies remove the spare, the jack and the tyre lever from all their vehicles to prevent theft.
No need to ask me how I know this!
I aim to check my tyres once a month and the engine oil level at the same time. So far so good.
Good point. The Slime pump for motorcycles goes to 300 psi, but of course there’s that flow rate issue (= takes a long time). Best bet (if your car has a high-pressure spare tire) might be a cheap pancake-tank compressor that you plug into the wall, fill, and then unplug and carry to your car.