Tyres, load index and a space-saver before a 900 km trip

Replace both rear tyres. The front pair can stay for this trip.

• The legal minimum tread depth in Switzerland is 1.6 mm in the main grooves. The rear right at 1.3 mm is already illegal and would fail the inspection; on a wet road it also lengthens braking noticeably.
• A 2 cm sidewall bulge is a structural defect after a kerb strike. It must be replaced no matter how much tread is left, because a blowout at motorway speed with four people aboard is a realistic outcome.
• Replace as an axle pair. Rear left at 2.4 mm is legal but worn; pairing it with a new tyre gives uneven grip on the same axle, especially in the wet, and the ESP will be correcting a mismatch instead of a road surface.
• Load index 91 means 615 kg per tyre. Front axle 1,010 kg gives 505 kg per tyre; rear 950 kg gives 475 kg. Both are well below 615 kg, so the load index is not a limit with four adults and luggage, but only if you raise the pressure by the 0.3 bar the handbook specifies, because the rated load assumes the correct pressure.
• The front tyres at 4.1 mm and 4.0 mm are legal; plan to replace them before next winter rather than now.

No. Use it only to reach the next workshop.

• The 80 km/h sticker and the 125 mm width are not suggestions. A space-saver has a much smaller contact patch, less grip and often a different rolling circumference, which keeps ABS and ESP working and changes the car's behaviour under braking.
• Load index 96 (710 kg) means the weight at that wheel position is not the limiting factor; speed and handling are. One wheel at 80 km/h while the others could run faster also produces an unstable car in an emergency stop.
• 900 km with four adults and luggage, in rain and possible snow, on a temporary wheel, is far outside its intended use. Typically it is meant for 50-80 km at reduced speed to the nearest garage.
• Practical preparation: check the space-saver's pressure before you leave, since they lose air over months, know where the jack and the wheel bolts are, and if you have to fit it, drive to a tyre dealer and have the damaged tyre repaired or replaced the same day.

Fit winter or all-season tyres before you go, and plan for chains on the passes.

Switzerland does not set a date; it sets a standard of care. The vehicle must be in a condition suited to the conditions on the road. A driver who blocks a road on summer tyres in snow can be fined, and after a crash an insurer can reduce benefits for a failure to meet that standard. With snow forecast above 800 m, summer rubber does not meet it, whatever the tread depth.

Practical consequences:

• Prefer winter tyres with the three-peak-mountain-snowflake marking; an M+S marking alone is weaker. They also help on cold, wet asphalt below about 7 degrees with no snow at all.
• Carry chains if your route crosses a pass where they may be required, and practise fitting them in daylight, not on a snowy shoulder at night.
• Check the pass and road reports that morning, plan an alternative, and keep the tank full with water and a blanket in the car, because closures can last hours.
• Match speed and following distance to the conditions. Winter tyres shorten the stopping distance; they do not remove the need for it.