How to Change a Flat Tyre Safely

Before You Touch a Wheel, Sort Your Location

A flat tyre is rarely convenient, but where you stop matters far more than how quickly you can fix it. If the tyre goes down while you are moving, keep both hands on the wheel, ease off the accelerator and let the car slow naturally. Stamping on the brakes can drag you towards the damaged side, and a sudden swerve at speed is how a nuisance turns into an accident.

Signal early and pull as far left as you can — a verge, a lay-by, a quiet side street, or a supermarket car park. Look for level, firm ground rather than soft grass or a slope, because a jack on uneven or boggy surfaces is a jack waiting to slip.

On a motorway, the honest advice is that there is no safe place to change a wheel. Aim for the next exit or an emergency refuge area, which gives you a marked bay and a telephone linked to the control centre. If you genuinely cannot reach one, park on the hard shoulder as far left as possible, turn the front wheels towards the kerb, switch on your hazard lights and get every passenger out through the doors facing away from traffic. Everyone should wait behind the barrier, well clear of the car. Leave the warning triangle in the boot on a motorway — walking back up a live carriageway to place it is far more dangerous than doing without it.

Know What Is Actually in Your Boot

Many modern cars leave the factory with a sealant kit instead of a spare wheel, so check before you need it on a wet night. Open the boot floor, lift the carpet and see what you have.

• Spare wheel: either a full-size wheel or a skinny space saver, usually painted bright colours to remind you it is temporary. Check its pressure every few months — a spare at 20 psi is no spare at all.
• Jack and wheel brace: the scissor jack supplied with the car is fine for a single wheel change. If you own a heavy estate or a van, consider keeping a small trolley jack and a breaker bar at home.
• Locking wheel nut key: often tucked in the glovebox or with the jack. Without it, the locking nut will not budge. Note the key code and keep it somewhere safe.
• Extras worth carrying: a hi-vis vest, a torch, a pair of work gloves, a tyre pressure gauge and a rain jacket. Cheap, and they make the job far less miserable.

Loosen the Wheel Nuts Before the Car Goes Up

This is the step most people get wrong. Once the car is in the air, a stubborn nut will simply spin the wheel instead of undoing.

First, secure the car: handbrake firmly on, engine off, car left in first or reverse gear if it is a manual, or in park if it is an automatic. If you have a chock, or simply a brick, wedge it behind a wheel on the opposite side.

Prise off the plastic wheel trim or hubcap if your car has one, then fit the brace onto each nut and turn it anti-clockwise a quarter of a turn. Do not remove them yet — just crack them loose. If a nut refuses to move, stand on the brace with your foot rather than yanking at it, keeping your weight steady and your back straight.

Jacking the Car Without Damaging It

Your handbook will show the reinforced jacking points, usually a small notch or arrow along the sill, roughly a hand's width behind the front wheel or ahead of the rear one. Line the jack up squarely under that seam, not under a floor pan, a plastic cover or a suspension arm, all of which will bend expensively.

Raise the car steadily until the flat tyre is just clear of the ground — about an inch is plenty. Push the wheel you have removed under the sill as a safety block, and never put any part of your body underneath a car held up only by a scissor jack.

Swapping the Wheel

Undo the loosened nuts by hand and lift the wheel straight off, keeping your knees bent and your back upright. If it has seized onto the hub, a firm thump with the heel of your hand on the tyre wall usually frees it.

Fit the replacement, lining the bolt holes up with the hub, and hold it in place with one hand while you wind the nuts on by hand. Snug them up in a star pattern — opposite nut, then the next opposite — rather than working round in a circle. Then lower the jack and remove it.

Tightening Up and Getting the Puncture Repaired

With the car back on the ground, tighten the nuts properly in the same star sequence. A torque wrench set to the figure in your handbook, typically somewhere between 100 and 120 Nm depending on the model, is worth keeping in the garage. Without one, tighten firmly with the brace but do not jump on it — overtightened nuts can stretch the studs.

If you have fitted a space saver, remember the restrictions: usually a maximum of 50 mph and around 50 miles of use, with a much higher inflation pressure than a normal tyre. A full-size spare needs checking too.

Finally, have the punctured tyre inspected properly. A nail in the tread can often be repaired, but sidewall damage or a run-flat that has been driven on flat usually means a new tyre. Recheck the wheel nut torque after around 50 miles, and check your tyre pressures monthly — most flats are slow leaks that announce themselves long before the tyre goes completely down.