Thursday, January 3, 2019

Emergency Air for Tires

I've written about tires before, such as how to plug holes and how to find a spare, but today I want to touch on how to put air back in a low or flat tire in a pinch.

I've dealt with slow leaks over the years. Sometimes it takes four or five trips to different tire shops before they finally find the cause, but until they do I'm always at risk of finding a tire low or flat when I want to drive. Another thing that used to be common was needing the spare tire in the trunk and finding it low or flat. The causes are varied, such as from a small nail that is hard to find or a leaky valve stem, but rather than replace rather expensive tires just because the technicians can't find a leak I carry a portable air compressor.

I started carrying one after working with a couple of guys who liked to take their trucks and toys off-road a lot. They would often lower the pressure in their tires to get better traction when driving in sand, and they needed to get the pressure back up to normal before hitting the pavement on the way home. Their solution was to always carry a 12V air compressor to do the job, one that plugged into a cigarette lighter. This sounded like a good idea, so I bought a cheap 12V air compressor and tossed it in the trunk of the car. It has come in handy several times over the years.

There are a lot of models on the market, and the prices range from $10 to well over $100. I bought mine at Harbor Freight a long time ago, and that model is no longer made, but they still sell similar compressors. Northern Tools is another source of inexpensive models that will get the job done. Most auto parts stores will carry something similar, and of course you can always find them on Amazon

Here are a few things to look for, and to look out for:

  • Almost all of the models I've seen are made overseas, so quality is going to be poor to fair. I suggest testing any model you buy before putting it in your trunk, in case you get a lemon that has to be returned. 
  • Gears and cases are going to be made of plastic and aren't designed for extended use. Expect them to be “oil-less”, which means the bearings and cylinder/piston fittings are going to be short-lived. These are true emergency gear, not something you'll be using every day unless you spend a good chunk of money. 
  • Heat is the main enemy of small compressors, so let them cool down in between inflation jobs and monitor them on larger jobs. If they get hot to the touch, pause the job and let them cool down. This will greatly extend the life of your compressor.

  • The 12V connection is usually a generic plug-in that fits into a cigarette lighter or power port and looks like the car charger for a phone. Some of the more robust or higher pressure models will come with small clamps that grip the posts on your car's battery; this is needed if the compressor requires more power than what is available from a power port (normally around 200W).
  • The end of the hose that fits on the valve stem is going to be either a standard straight fitting or a right-angle locking fitting. I prefer the locking style because these compressors are small and slow, and it can take 10 minutes to air up a completely flat tire. That's a long time to be squatting next to the car holding an air chuck on the valve stem, especially if it's raining or you're near traffic.

  • Most models will come with a built-in pressure gauge. The precision and accuracy of these gauges is on par with the construction of the compressor itself, so use it as an approximation of what is really going into your tire. The newer version come with digital gauges, which have a slightly higher standard of construction and should be a bit more accurate. 
  • Carry a good tire gauge as part of your normal vehicle kit and double-check the pressure when you're done.

  • A lot of models have some sort of built-in light. This can be very helpful if you're working in the dark. My old compressor has an incandescent bulb, but the newer one use LEDs. 
  • The best models will have a flashing mode to warn other traffic that you're there. 
  • Having a light on the compressor frees up your flashlight for other work.

  • I'm sure you've all heard an air compressor before; they're loud. These little ones can be just as loud as the larger ones, maybe even louder. Noise is caused by vibration, which is a common problem on these small compressors. The lack of quality control means that the moving parts aren't always perfectly balanced and they vibrate more than a good compressor. 
  • The little ones also tend to run at a much higher speed, which increases the noise and reduces the life of the moving parts.

  • Most of the little compressors will come with a bag of fittings for inflating air mattresses and balls. This is a nice additional use, and if you're lucky may be more common than airing up tires. 
  • I've seen several of the newer models some with a soft-sided case or a hard-shell plastic box. This will help keep all of the parts and pieces together in your trunk or toolbox and will prevent damage to cords and hoses, so this is a definite plus. 
  • Cordless models are starting to pop up, but I've not had a chance to play with one. I'm leery of rechargeable batteries in emergency gear, since they tend to require periodic recharging if you try to store them. Pulling out a flat spare tire would only be made worse by trying to inflate it with a dead compressor. I also doubt that a rechargeable battery would be able to power a compressor long enough to inflate anything larger than a motorcycle tire, especially after a year or two of storage or use.

For something that costs less than $100, this is a good addition to any car's emergency gear. Get the best you can afford and learn how to use it before you need it, just like any other emergency equipment.

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