Safety First
Pull your car into a safe spot, even if it means driving on the flat tire. Driving more than a few feet with no air pressure will ruin your tire and maybe even the rim. On the other hand, being rear-ended by a high-speed vehicle that couldn't see you because you were parked on the road around a curve will ruin more than that. Try to pick a spot that's flat and dry, and has solid support.
This Is Supposed to Be Easy, Right?
The spare tire, jack and lug wrench that came with your car will make it technically possible to change a flat. You might want to carry around a few extras. I do.
First problem: The spare is flat, too. You check the air pressure in your spare tire regularly, right? Throw an inexpensive 12-volt air compressor into the spare tire well. This might let you add enough air to get you home to change the spare at leisure in your dry, well-lit garage. I also suggest carrying disposable Tyvek painter's overalls, some gloves, rags and hand cleaner. And a flashlight--one with batteries that work.
First Things First
I'm going to give you some homework to do this weekend--before you get a flat. Go out to your car and loosen all of the lugs a half-turn, and then retighten them. Odds are that the last mechanic to work on your car used an air gun to tighten them, and you'll need to struggle with them. Loosen the lugs one at a time and tighten them to the manufacturer's specified torque, generally between 75 and 100 lb.-ft. I strongly recommend the use of a torque wrench (about $25) to do this. Do not simply tighten them until they squeak and throw off little clouds of rust. And loosen and retighten in a star pattern, not going round and round in a circle.
Oil or Not?
Some car manufacturers use a proprietary coating on their lugs, and say that no lubrication is necessary. Others specify they should be lightly lubed. I prefer to lubricate, because then the torque you're so carefully applying to the lugs will be far more accurate. A small dab of grease or engine oil will make it much easier to break the lugs free when you have to. And no, it won't make your lugs spin off by themselves, at least not if you've torqued them properly.
By the Side of the Road
Okay, your tire is flat and you've parked off the road surface on flat ground. Set a safety triangle or a flare 75 ft. behind your car to warn traffic. Start by using a couple of pieces of wood or a roadside rock to chock the wheel opposite the flat both in front and back. Set the handbrake and leave the gearshift in Park (or Reverse if you have a manual).
Remove any hubcap or trim. Loosen the lug nuts or bolts. They're movable, right? The lowest-tech solution is to use a piece of water pipe as an extension on the lug wrench's handle. Around 3 ft. of pipe makes the tightest lug a one-hand job. No pipe? Try standing on the end of the wrench and bouncing up and down. Unfortunately, this is likely to cause the wrench to pop off the lug and whang your ankle, so be careful.
We carry an old-fashioned four-way wrench. Because you can push with one hand and pull with the other, the socket stays planted on the lug and you can generate lots of torque.
Leave one lug on--one near the top of the wheel--a couple of turns from tight. Put the others someplace where you won't scatter them into the weeds by accident.
Upsy-Daisy
Lift the vehicle until the wheel is unloaded, run off the last lug and pull it free.
What? The wheel won't budge? Sit down on the ground and kick the sidewalls with your feet, alternating left and right until it pops loose, but not so fiercely as to knock the car off the jack. Still stuck? Put two lugs back on fingertight, and then -loosen them one turn. Remove the jack, and drive back and forth a few feet three or four times while slamming on the brakes to break it loose.
Together Again
Now is the time to clean any foreign matter from the mating surface and centering ring of the hub and wheel to ensure the wheel runs true and stays properly torqued. Wire brush both surfaces and apply a light coat of antiseize compound to prevent a stuck wheel in the future. Thread all the lugs back on fingertight. Spin the wheel a couple of times to center it, and tighten the lugs slightly with the wrench.
Now you can lower and remove the jack. Tighten the lugs again, in a crisscross rather than a circular pattern to keep the wheel true. The last step is to tighten the lugs to their final torque.
(1) Chock the opposite wheel with scraps of wood, tree branches or partially flattened soda cans.
(2) Stock lug wrench is often inadequate to the task of un-torquing lug nuts. Use a pipe extension. Leave wheel on ground to keep it from spinning.
(3) Jack will have someplace to peg to its intended location on the bottom of the car.
(4) This jack attaches to the frame rail while others may have a small recess on the pinch weld along the bottom of the body.
(5) The owner's manual should show where to place the jack, and some vehicles even have a decal on the jack itself or on a tag in the tool bin.
(6) A little grease on the jack's screw will reduce effort. Don't overdo it or the grease will get on everything.
(7) On soft ground or hot asphalt it's a good idea to use a chunk of 2 x 6 to keep the jack from spelunking down.
(8) Toss the old tire under the car in case car falls off the jack. Clean the hub before mounting the new tire.
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