After a flat, you fit the compact temporary spare from the boot. What is the correct way to treat this spare tyre?

Why C is correct

The compact spare is engineered to a single job: move the car a short distance at reduced speed so the real tyre can be fixed. It is lighter and narrower than a road wheel, has shallow or no tread pattern, changes the car's braking and handling balance, and its durability is measured in tens of miles rather than thousands. Leaving it on the car for weeks means driving on a component that was never designed for the speeds, loads or distances of ordinary use, with handling and braking quietly degraded the whole time.

Why the other options are wrong

A. It performs better than a standard tyre in rain and can be kept until it wears out

Wet performance is where the temporary spare is weakest, not strongest: minimal tread depth and a narrow contact patch are the ingredients of long stopping distances and early hydroplaning, not of grip.

B. It is a normal replacement and can stay on the car indefinitely

'Indefinitely' is the exact opposite of the design intent. Every property that makes the spare small and storable — narrow section, light construction, minimal tread — is a property that disqualifies it from service as a normal tyre.

D. It may be run at any speed provided the flat tyre is in the boot

The speed of the spare is the issue, and it does not care which wheel is in the boot. The constraint travels with the tyre on the car, not with the flat one in the luggage.

On the road

A screw in the left rear on Tuesday; the compact spare goes on and the car feels subtly wrong for the rest of the week — longer stops, a vague rear end in the wet. The tyre shop fits the repaired wheel Thursday morning. Two days on the spare taught the whole lesson: the little tyre was a taxi ride for the car, not a replacement wheel.

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