How to choose
Full-size or temporary spare wheel
A full-size spare wheel is the same size as the other four, so you can drive on it as normal. It does take up more room in the boot and weighs more. A temporary spare is a narrow rim with a narrow tyre. It fits into a smaller well, but it is only meant to get you to a garage or home, not for everyday driving.
If you choose a full-size wheel, keep the roadworthiness test rule in mind: the rims on a car must all be the same size unless the car manufacturer specifies otherwise. You will find the sizes the manufacturer allows in the owner's manual or on the sticker in the driver's door frame.
Speed and distance limits
For a temporary spare wheel, the manufacturer sets how fast and how far you may drive on it. The speed limit is usually 80 km/h, but it can be different for a particular wheel. The permitted distance also varies from one manufacturer to another. The speed limit is usually printed on the wheel's sticker, and you will find both limits in the owner's manual.
The sticker usually shows the tyre pressure too. A temporary tyre often needs a higher pressure than your regular tyres, so check it before you put the wheel in the boot. A narrow wheel changes how the car brakes and handles in corners, so drive gently and refit your regular wheel as soon as you can.
Bolt pattern and centre bore must match
A spare wheel has the same requirements as any other rim. The bolt pattern (PCD) must be exactly the same as your car's hub, because roadworthiness rules do not allow rims with a different bolt pattern. The centre bore (DIA) must not be smaller than the hub centre. If it is larger, the wheel has to be centred with hub-centric rings. Check the offset (ET) as well: it determines how close the wheel sits to the brake caliper and the bodywork.
Check the wheel bolts and nuts separately. The seat of the bolt head has to match the rim, and a steel spare rim may use a different seat from your alloy rims. In that case your existing bolts will not seat properly on it, and you need bolts with the matching seat.
What is included
Spare wheel kits differ. Some come with a jack and a wheel brace, others with just the wheel. You can see exactly what is included on the product page. If your car has no jack because the factory supplied a tyre repair kit instead, get the wheel together with the tools.
TPMS sensors
If your car has TPMS sensors (tyre pressure sensors) but the spare wheel does not have one, the system gets no signal from that wheel. So while it is fitted, the tyre pressure warning light may come on. This is to be expected. Once you refit your regular wheel with its sensor, check that the light goes off.