Automobile Repair/Flat tire

right|frameless|290x290px|A flat tyre A flat tyre is the roadside repair most drivers will face at some point. Changing a wheel is a half-hour job with the tools supplied in the car, provided the spare is inflated and the procedure is followed in the right order. Many newer cars carry no spare at all, only a sealant-and-compressor kit; check which you have before you need it. Before you need it Know where the spare, the jack and the wheel wrench are (usually under the boot/trunk floor, sometimes under the rear of the car or inside the engine bay on vans). Check the spare's pressure when you check the other tyres. A space-saver spare usually needs a higher pressure than the road tyres, often about 4.2 bar (60 psi); the figure is on its sidewall. If the wheels have locking nuts, keep the key in the car and know where it is. Keep a pair of gloves, a torch and a warning triangle with the jack. Procedure +StepWhat to do1Slow down gently and stop on firm, level ground as far from traffic as possible. Switch on the hazard lights, apply the parking brake, and put an automatic in Park or a manual in first or reverse gear (not neutral). Place the warning triangle behind the car. Get passengers out and away from the road.2Chock the wheel diagonally opposite the flat one with a stone or a block if anything is available.3Remove the wheel trim if there is one. With the wheel still on the ground, loosen each wheel nut about half a turn with the wrench, turning anticlockwise. Use body weight on the wrench rather than kicking it. Do not remove the nuts yet.4Set the jack at the jacking point nearest the flat wheel. The points are marked on the sill or shown in the owner's manual; jacking anywhere else can crush the sill or let the car slip. Raise the car until the flat tyre is clear of the ground by a few centimetres.5Remove the nuts, keeping them together where they cannot roll away, and lift the wheel off. Lay it flat under the sill as a safeguard in case the jack fails.6Lift the spare onto the studs (or, on cars with bolts, hold the wheel against the hub and start one bolt by hand). Fit all the nuts by hand, then nip them up with the wrench, working in a star pattern (opposite nuts in turn) so the wheel seats evenly.frameless|Space-saver spare fitted7Lower the car until the tyre carries its weight, then tighten the nuts firmly in the same star pattern. Lower the jack fully and remove it. Stow the flat wheel and the tools.8Check the spare's pressure at the first opportunity and have the nuts tightened to the specified torque (typically 100 to 140 N·m on passenger cars) with a torque wrench. Re-check the torque after about 50 km. Driving on a space-saver spare A narrow temporary spare is marked with a speed limit, usually 80 km/h (50 mph), and is intended for the distance to a tyre shop, not for continued use. It changes the car's handling and braking, and on many four-wheel-drive cars it should go on a non-driven axle, or be used only for the shortest distance, because of the difference in rolling diameter; the owner's manual says which. Traction control and ABS may show a warning while the spare is fitted. Sealant kits Cars without a spare carry a bottle of sealant and a 12-volt compressor. The sealant is injected through the valve, the tyre is inflated, and the car is driven a short distance to spread it. The kit will seal a small puncture in the tread but not a sidewall cut or a tyre that has come off the rim. A tyre repaired with sealant must be inspected and either repaired properly or replaced; tell the tyre shop that sealant has been used, as it has to be cleaned out and may make the pressure sensor unusable. When not to change the wheel yourself On a motorway hard shoulder, on a slope, on soft ground, or at night in traffic, it is safer to wait behind the barrier and call for assistance than to work beside moving traffic.