Flat tires are never a fun thing—but this one takes the cake. It’s late, of course, and in the middle of a frog-choking rain. You’re stuck in the ankle-deep mud on the shoulder of a deserted road. How deserted? Out-of-cellphone-coverage deserted, or you’d be sitting in the cab of a service truck while somebody else gets drenched. That’s how deserted.

Yes, you could drive along the shoulder on the rim for a few miles to civilization, but insurance won’t cover the damage to your expensive alloy rim. It’s time to knuckle down and put on the spare. A pressure can of flat-fix foam can get you home if the problem is a simple puncture, and that may be a viable option, especially for smaller individuals or the elderly who would have a tough time changing a tire. Just remember two things: This stuff is a temporary solution, and the flat will need to be attended to by a tire technician at the earliest opportu-nity. Be sure to warn the technician that you’ve used this stuff. The propellant is flammable, and unless he’s warned, he stands the chance of causing a nasty explosion.

This project was originally published in the November 2002 issue of Popular Mechanics. You can find more great projects at Popular Mechanics DIY Central.

Step 1: Be Prepared

First of all, remember to check the pressure in your neglected spare tire whenever you check the pressure in the other four, which you do faithfully every month or so, right? A flat spare is no help. And if you’re like most people who save a plugged or nearly worn tire for the spare, it’s likely that the spare has a slow leak, which would leave you stranded.

Furthermore, you’ll never be able to change a tire if you don’t have the basics—a jack and a lug wrench. Go back into their hidy-hole and confirm their existence. While you’re there and you have enough light to read the owner’s manual, figure out how to unship them and make sure the jack isn’t rusted into immobility. Check the manual and find the vehicle’s jacking points. You’ll probably need to lie on the ground to find them, but this will be a lot more palatable now in your driveway than later on the shoulder of some mud bog.

Step 2: Grunting Helps

The most common difficulty in changing a tire is lugs that are tightened far too tightly. A casual rattle with a mechanic’s air wrench can deliver a tightening torque that only a pro wrestler could remove with the stock lug wrench. Wheel lugs need to be tightened to no more than the manufacturer’s recommended torque to ensure they won’t loosen. Check your owner’s manual, but the figure will be 75 to 100 ft.-lb. of torque. Do the math—that means a 200-pound adult should be able to tighten the lugs by placing all his weight on top of the wrench only 6 in. away from the fastener.

A few drops of engine oil or grease on the threads and the lug chamfer (where the lug touches the wheel, not the threads) will prevent galling and seizing. When removing a wheel, first loosen all of the lugs in a crisscross pattern a half-turn or so. It may be necessary to use the mechanic’s favorite cheater bar—a piece of water pipe or muffler pipe about 4 ft. long—to add enough leverage to break the lugs loose. Remove them one at a time and lube them if they squeak. Retighten them in three stages, again in a crisscross pattern.

Step 3: Black and Round

Many carmakers, in an attempt to reduce vibration by making sure the wheels are more concentric with the hub, use a protruding lip that mates closely with the centerhole on the rim. This works well for a couple of years, but eventually corrosion from road grime can make it impossible to budge the wheels, even after you’ve loosened all the lugs. Correct this now, and you won’t need to try it in the field. Jack up the corner of the car to take the load off the wheel and kick the wheel, alternating sides until it pops loose.

No joy, and now your feet hurt? Be sure the lugs are only a single turn from tight, lower the car and move it a foot forward and back, rapping the brakes smartly to break the wheel loose. A shot of penetrating oil may help in an hour or two. Clean up the corrosion with emery paper and coat all the surfaces lightly with wheel bearing grease, Vaseline or, best of all, antiseize compound.

You’ll need a few things besides the on-board tools for your emergency tire change. Pack a flashlight with good batteries or, better yet, a cigarette-lighter-powered trouble light, an emergency triangle, a couple of road flares, some gloves and a poncho or ground cloth. Toss in three pieces of scrap 2 x 4 as well, each about a foot long.

Step 4: That Fateful Day

When changing a tire the first, and most important, thing to do is to get the vehicle to a safe area, far enough from the road to save you from becoming road pizza—particularly if the flat is on the left side and your back side will be poking out into traffic while you work. Set your triangle or flares 100 ft. or so upstream. Leave the vehicle in Park and set the handbrake. Block the wheel diagonally opposite the flat with two pieces of wood. Loosen all the lugs on the flat a full turn.

Take the spare out of the trunk and put it halfway under the car near the jack. In the unlikely event the car falls off the jack, it will only fall onto the spare—not your foot or head—and will leave you a fighting chance of raising the car and continuing. If the car falls to the ground, you’ll have no way to raise it. Raise the jack from its stowed position to nearly high enough to contact the bottom of the car. If you’ve got a different style of jack than the one pictured here, check your owner’s manual for specifics. If the ground isn’t firm, put the third piece of wood under the jack point, and the jack on top of the wood.

Be sure everything is level. Jack the car up until the flat clears the ground by several inches, because the spare isn’t flat and will need more clearance. Remove the lug nuts, and put them inside the hubcap or in some other place where they won’t get lost in the dark, or accidentally scattered into the weeds by your feet. Pull the flat off and put it halfway under the car. Hang the spare on the studs. No studs? You’ve got lug bolts (common on many European cars) and you’ll need to juggle the wheel while you get the top one started.

The easy way is to sit down on the ground facing the hub and balance the spare on your toes while you start the first lug bolt. If you begin with the top bolt, the wheel will hang gracefully from it and you can start the rest. Finger-tighten all the lugs and then lightly tighten them with the lug wrench, again in a crisscross pattern. Be sure you don’t have anything (like a stone or mud) trapped between the rim and hub, or the rim will wobble. In fact, if the mud compresses later, the lugs could lose their torque and the wheel could fly off. If you need to, remove the wheel again in the morning to remove the debris, corrosion and rust from all the mating faces and between the wheel and hub, and then lightly lube.

This will have the added benefit of making the wheel easier to remove the next time. Hint: There should be some grease to be found on the jackscrew of your jack, and there’s probably enough to put a smidgen on the lugs with your finger. Be sure to get it on the mating chamfer as well as on the threads. Lower the vehicle and pull the jack out. Now you can tighten the lugs to their correct torque.

Check the owner’s manual for the torque specification. Measure carefully. If the lug is dry and unlubricated, it may take a lot more force to tighten the lugs. The only accurate way to torque the lugs is to use a mechanic’s torque wrench. These can be purchased for 20 bucks or so. If you have expensive alloy wheels, you may want to buy one and keep it in the trunk. As you’re putting away your tools and jack, be sure you haven’t left them covered with mud or moisture, which might cause them to rust while stored. If they’re a mess, clean them and relubricate at your earliest convenience.