New tyres
New tyres fitted where the car is parked
Having new tyres fitted at the car saves a trip to a tyre centre and a wait in a reception area. The work is the same as in a workshop: the old tyre comes off the rim, the new one goes on, the wheel is balanced and refitted, and the nuts are tightened to the maker's torque figure.
Reading the size on your sidewall
The size is the string of figures on the tyre wall, such as 205/55 R16 91V. The first number is the width in millimetres, the second is the sidewall height as a percentage of that width, R means radial construction and the last number is the rim diameter in inches.
The part after the size, 91V in that example, is the load index and speed rating. A replacement should match or exceed both, and the two tyres on one axle should be the same size and pattern.
One tyre, a pair or all four
One new tyre is fine when the others still have plenty of tread and match it in size and pattern. A big difference in tread depth across one axle makes the car brake and corner unevenly.
Four-wheel-drive cars are more sensitive to differences in tread depth between tyres, so check the handbook before replacing just one.
Pressure sensors and run-flats
Many cars have a tyre pressure sensor fitted inside each wheel, usually on the back of the valve. Mention it on the call, because the sensor stays with the wheel when the tyre is changed.
Cars that left the factory on run-flat tyres usually need run-flats again, and run-flat and standard tyres should never be mixed on one car.
What the fitter needs at the car
A driveway, a residential street where parking is legal or a workplace car park all work. The jack needs firm, level ground and there has to be room to work around the wheel.
Supermarket, retail park and station car parks are private ground, so the owner's permission comes first.