Five adults, a roof rack and a bulge in the sidewall
Saturday, 05:30, still dark. You plan to leave at 06:00 with four adult passengers and luggage for a 420 km drive to a wedding. The tyre placard on your 2016 hatchback gives 2.2 bar front and rear for a normal load, and 2.4 bar rear for a full load. Working by torchlight you find: the left rear tyre has a golf-ball-sized bulge in the inner sidewall, and tread reads 2.1 mm at the centre but 1.2 mm on the shoulder; cold pressures are 1.8 bar on all four tyres; the space-saver spare is at 1.5 bar and its sidewall states 4.2 bar and 80 km/h maximum; the left headlight is noticeably dimmer than the right; the brake fluid sits on the MIN mark; the wipers smear; and the low tyre-pressure warning light is on. A roof rack carries a hard suitcase and a foam mattress, held by two nylon straps and a bungee cord.
1. Sort the findings into (a) do not leave until fixed, (b) fix before departure today, (c) legal but worth flagging. Explain the reasoning for each, not just the verdict.
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(a) Do not leave. The sidewall bulge is structural - the cords are broken and no repair is legal or safe. Under five adults on a hot road at freeway speed the tyre can burst with no warning, and a rear blowout in a loaded hatchback ends in a spin. Brake fluid on MIN is the second stop item: fluid does not evaporate, so it is leaking or the pads are worn to the limit. Either way the pedal can go long or to the floor, and you cannot check it at 110 km/h with a full car.
(b) Fix today. Pressures (1.8 against a required 2.2/2.4), the space-saver at 1.5 bar instead of 4.2 bar - it would be useless in an emergency - the dim headlight, since you leave in the dark, the smearing wipers, and the roof load, which is not tied down for a 420 km trip.
(c) Legal, but flag it. The 1.2 mm shoulder tread is above the 1 mm minimum, yet at that depth the tyre clears almost no water. The warning light is a symptom of the pressures, not a separate fault.
2. Show the pressure and load reasoning for the trip: what should the tyres read, and what does the bulge mean physically?
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The placard is read for the load you actually carry, not for the load you normally carry. Five adults plus luggage is a full load, so set 2.4 bar rear and 2.2 bar front, measured cold - which 05:30 in winter conveniently is. The current 1.8 bar is 0.6 bar under specification; under-inflated tyres flex their sidewalls far more, generate heat, and are the standard route to a blowout on a long hot run. Do not compensate by over-inflating to 'allow for the load' - that reduces the contact patch and grip.
Inflate the spare to 4.2 bar so it is usable at all, but remember the 80 km/h limit and short distance - it is a limp-home device, not a tyre for a 420 km wedding trip.
Physically, the bulge is a section of sidewall with broken casing cords, so the pressure is contained only by rubber. It bulges more as it heats, and it fails on the inner side where you will not see it. That is why it is a replacement, never a repair.
3. You have limited tools and a 06:00 departure. Set out your practical recovery plan, and state what you would refuse to do even under family pressure.
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Practical plan: accept the delay. A tyre fitment centre that opens early, or a fuel station with a bay, can fit one tyre - and on a mismatched set it should go on the rear axle with the best tread. Inflate the other three to placard, top up and investigate the brake fluid before moving at all: if it is a leak, the car stays. If a replacement cannot be done by mid-morning, use a second vehicle or postpone; nobody remembers which wedding you reached on time, everyone remembers the funeral.
Refuse the following: driving on the bulged tyre 'just to the next town', driving with brake fluid at MIN, running the space-saver at freeway speed for 420 km, and carrying the suitcase and mattress on two straps and a bungee. A roof load must be fixed at four points, kept within the rack's limit (often 50–75 kg), and treated as a handling change: the centre of gravity rises, braking distances lengthen and side winds push you across a lane.