Loosen the lug nuts before you lift the car

You have a flat, or you are working out what you would do if you got one. Some people say they have never changed a tire. This is a job where the order of the steps decides whether it goes smoothly or somebody gets hurt, and the nuts on the wheel can be hard to turn.

If you are on a motorway, a busy road, or anywhere you cannot get completely out of the traffic, this page is not for you right now. The box above says what to do instead.

Loosen the lug nuts a little while the tire is still on the ground, then lift the car, and keep every part of you out from under it.

Many people give the first half of that as the opening step of the job. Some people say the reason is simple: on the ground the wheel cannot spin while you push on the wrench, and the jack is not strained by it. A vehicle maker’s owner’s manual puts it the same way. It says to turn each nut about one turn counterclockwise and not to take any nut off until the tire is off the ground. Some people point out that on most cars the wheel hub carries the car’s weight, not the nuts. The manual’s one-turn step is the one to follow.

Some people call this too basic to count as a tip. Others answer that a step looks obvious only to someone who has already learned it, and that people can forget it in an emergency. If you had not heard it, you are not slow.

Before you touch the wrench

Where you do the job matters more than how. A US state transport department’s breakdown guide says not to try to change a flat in or near a lane of traffic: it is better to ruin a tire or a wheel than to risk being hit. A vehicle maker’s owner’s manual says to move completely off the road onto level, firm ground. It says to switch on the hazard lights, put an automatic in park, set the handbrake and turn the engine off. It also says to block the front and the back of the wheel diagonally opposite the one you will lift, and to let nobody stay in the car while it is on the jack. Anyone with you should wait well away from the road.

One person points out that park alone only holds a car while both driving wheels are on the ground. If one is lifted, the other can still turn, especially on a slope. That is one reason the manual asks for the handbrake and the blocks as well.

Loosen first, then lift

The manual’s step is to break each nut loose about a turn with the wheel wrench, with the tire still down, and leave every nut on. Some people suggest a mat or knee pads, because kneeling on gravel or hard ground is hard on the knees. One person suggests keeping a breaker bar and a socket in the car for very tight nuts. One person points out that wheels are not supposed to be that tight, and that shops using power tools often over-tighten them.

Lift at the right points, on ground that will not give

A vehicle maker’s owner’s manual says to put the jack only on the car’s designated jacking positions, never on the bumpers or any other part. Some people say the points are on the side of the frame, often marked with a notch or an arrow, and not under the fender. Some people point out that an owner’s manual shows the points for the small jack that comes with the car, while a service manual lists others for a floor jack, so a point that suits one jack may not suit another.

Some people say small scissor jacks are unreliable because a slight shift can drop the car. One person warns that a scissor jack on a slope or on gravel will fall, and another suggests a piece of plywood under the jack on soft ground. One person warns that a jack handle can spring back and injure you if it slips. Keep anyone out of the car while it is up, as the manual says.

Keep your body out from under it, and put the wheel there instead

Many people warn that a hydraulic or scissor jack is for lifting and lowering, not for holding a car up while somebody is under it, and that rated jack stands are what hold it. For a tire change you do not need to be under the car at all. One person says every step can be done from the side, and a vehicle maker’s owner’s manual says never to put your body, or any part of it, under a car held up by a jack.

Many people also suggest sliding the wheel you have just taken off under the car, near the jack, so that if the jack gives way the car comes down on the wheel and not on you. One person points out that it must be the whole wheel with its rim, not the rubber tire alone. Some people argue about it: some call it a sound emergency backup if the jack fails and you have no stands, and others call it dangerous and say only rated stands should hold a car if anyone is going under it. Either way it is a backstop for someone kneeling beside the car, not a reason to go under it.

If you want to work under a car, that is a different job, and there is a page on it: start with the oil and put the car on stands.

Put the spare on, and finish on the ground

A vehicle maker’s owner’s manual gives the order. Line up the holes with the studs and slide the wheel on. Put the nuts on and tighten them by hand as far as your fingers will turn them. Lower the car to the ground. Then tighten the nuts in a crisscross pattern, every other nut, until all are tight, and go round once more to check each one. One person warns that tightening nuts with the car still up on a scissor jack feels dangerous when the car is not stable.

One person warns that on steel wheels a nut put on with its flat side toward the wheel will not grip, will rattle and can damage the holes, and another points out that the pointed, conical end goes on first. Check the picture in your manual.

On torque, the manual gives a figure for its car and says to have it checked by a workshop. People disagree about whether you need a torque wrench for a temporary swap, and the questions below give both sides. One person says to tighten the nuts again after driving home from a shop that only ran them on with a power tool. If you practised the change on a calm day, one person warns you must tighten again after a short drive, and another says not to practise without a way to tighten the wheels properly.

The spare, and the tire you took off

A vehicle maker’s owner’s manual says a compact spare is for temporary use and must not be driven over 50 mph (80 km/h), and that the original tire should be repaired or replaced as soon as possible. One person says a step often missed is checking the air in the spare itself. There is a page on checking the spare and filling to the right number: check the spare and fill to the door sticker.

Some people warn that old worn tires can have exposed cords that cut hands badly, and another keeps gloves in the car with the spare.

Practise once, and know your kit

Some people suggest practising a change on a calm day, so that you know how it goes and that you have every part you need. One person says a practice run is not necessary: just make sure you have the jack, the spare and the key for locking nuts, and know where they are. Either way, look now, not at the roadside.

Who this page is not for

If you are on a motorway or a busy road, or you cannot get completely off the road, do not start. In the US, the state guide says to stay in the car with the flashers on and call for help. On a UK motorway, the Highway Code says not to attempt repairs. If you cannot physically kneel, turn a wrench or work a jack, or you are alone somewhere you do not feel safe, roadside help is the better choice. One person says roadside help is fine in a populated area but fails when you are far from anyone, so it is worth knowing how to do this if you travel far from towns. A car with no spare, or no jack, is not covered here.

If a car comes down on someone, call 911 in the US or 999 in the UK at once. This page does not cover freeing a person from under a car.