Pre-trip check before an alpine weekend
In late October you plan to leave Basel at 06:00 for a long weekend in the Engadin with three adult passengers and a full boot. The car is a six-year-old estate you bought privately three weeks ago. The tyres are 205/55 R16 91V with a DOT code of 2018, tread 3.2 mm at the front and 2.6 mm at the rear. The filler flap gives 2.1 bar for normal load and 2.6 bar for full load; you set 2.1 bar 'because that is the first figure on it'. On the roof there is a 55 kg box on the factory bars, and the manual states a roof load limit of 75 kg. There is no spare wheel, only a tyre repair kit dated 2019. On the right front tyre you notice a 4 cm bulge in the sidewall just above the rim. The forecast for the pass is 1 °C with snow showers above 1,400 m.
1. Which findings make the car unfit for this trip, and why?
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The sidewall bulge is a stop item. A bulge means the carcass cords are damaged and the tyre is delaminating internally. It cannot be repaired, and it fails under exactly the conditions of this trip: a fully loaded car, sustained motorway speed, warm tyres, then a cold mountain pass. The consequence is a blowout, usually at the worst moment. That tyre must be replaced before the car moves.
Tyre age. A DOT code of 2018 makes these tyres about seven years old. Rubber hardens with age regardless of tread; grip in the wet and on cold asphalt drops sharply, and the manufacturer's recommended replacement age (around 6–10 years depending on the maker) is being reached. On a car bought privately three weeks ago this is exactly what a pre-purchase check should have caught.
Tread depth. The legal minimum in Switzerland is 1.6 mm, so 3.2 and 2.6 mm are legal - but legal is not safe. Wet grip and aquaplaning resistance fall away below 3 mm, and 2.6 mm is nowhere near the 4 mm that makes sense for a winter trip.
The repair kit. A 2019-dated sealant is expired; the sealant polymerises and will not seal. Combined with no spare, a puncture on a Sunday in the Engadin becomes a recovery job.
2. What tyre pressures should you use, and how does the loading change the way the car behaves?
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Pressures. The flap is not a list to pick the first number from; it is a table of conditions. With four adults, a full boot and a roof box you are in the full-load condition, so 2.6 bar front and rear (or the higher figure the manual specifies for the rear axle). Check and set them cold, before departure, and remember that they will rise about 0.2–0.3 bar once warm - do not bleed them down. Under-inflation by 0.5 bar at full load generates heat, wears the shoulders and can destroy a tyre on a long motorway run.
Roof box. 55 kg is within the 75 kg limit, but the limit is for the box plus bars plus contents and it is easy to exceed with a few pairs of ski boots. Keep the box as far back as is compatible with the bars, and remember the manufacturer's reduced maximum speed for roof loads - often 130 km/h, sometimes lower.
Behaviour. The load raises the centre of gravity: more body roll, longer braking distances, and much greater sensitivity to side wind and to cross-winds at pass level. Adjust the headlight levelling for the rear load so you do not dazzle oncoming traffic. Secure everything inside: a laptop or a thermos becomes a missile in a 50 km/h impact. Finally, check the load index: 91 means 615 kg per tyre, so with a full boot and three passengers check the rear axle is not being pushed close to its limit.
3. The forecast shows snow above 1,400 m and your route crosses a pass. How do you decide whether to go, and on what basis?
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The legal position. Switzerland does not have a fixed calendar for winter tyres. What the law requires is that you remain in control of the vehicle; in wintry conditions that means tyres with adequate grip, which in practice means M+S or, better, three-peak-mountain-snowflake tyres with at least 4 mm of tread. Driving summer tyres into snow is a failure to control the vehicle, and it also shifts the insurance position if you crash.
Apply it to this car. You have 2.6 mm at the rear, a bulging front tyre, seven-year-old rubber and an expired repair kit. On dry autumn roads in the valley this would already be marginal; on a pass at 1 °C with snow showers it is not a decision to make - the car does not go as it is. Fix the tyre first, then decide.
Then judge the route. Check the live pass status (open/closed, chain obligations, snow line) shortly before departure rather than the night before. If the pass is doubtful, take the tunnel or the car-train and drive the last stretch on cleared roads. Leave earlier, drive slower, and plan for a stop rather than pushing on. A holiday is not worth a night in a mountain recovery truck.