Emergency Tyre Replacement Service

1. Definition and Applicable Scenarios

Tyre replacement rescue refers to an on-site service where emergency responders or vehicle occupants use on-board tools to remove a damaged tyre and install a spare tyre (including full-size spares, space-saver spares, or tyre repair kits) when a vehicle is rendered undriveable due to sharp object punctures, tyre carcass damage from road hazards, or high-impact blowouts. Its primary objective is to restore basic mobility, enabling the vehicle to clear hazardous road zones or safely reach the nearest workshop for professional repair or tyre replacement.

Applicable scenarios include: slow leaks caused by nails, screws, or other sharp metal objects puncturing the tyre tread; sidewall bulges or tears resulting from kerb impacts; severe tread cuts caused by running over sharp debris; and complete sidewall failure resulting from driving on severely under-inflated tyres.

2. Spare Tyre Types and Technical Specifications

Due to overall diameter discrepancies, prolonged use of a space-saver spare tyre causes excessive wear on the differential; it is strictly intended as a temporary fix. A full-size spare with a directional tread pattern can only replace tyres on the designated rotational side of an axle, whereas a non-directional, symmetrical tread spare can be fitted to any wheel position.

3. Standard Operating Procedures

• Phase 1: Safe Staging and Hazard Precautions

  • Activate hazard warning lights immediately and park the vehicle on a level, solid surface. Avoid changing tyres on bends or steep inclines.

  • Engage the handbrake firmly; shift automatic transmissions into 'P' (Park), or engage 1st gear or Reverse on manual gearboxes.

  • Deploy the emergency warning triangle at the mandatory distance behind the vehicle (≥50 metres on city roads, ≥150 metres on expressways). All occupants must evacuate and wait behind safety barriers.

• Phase 2: Tool Preparation and Loosening Wheel Nuts

  • Retrieve the vehicle jack, wheel brace, and locking wheel nut adapter (if equipped). Ensure the jack's rated load capacity exceeds the vehicle's kerb weight.

  • Before jacking up the car, use the wheel brace to loosen each wheel nut by roughly 1/4 turn in a diagonal criss-cross sequence. Note: The handbrake and transmission lock only secure the drive wheels, meaning the raised axle cannot be locked by engaging gear; apply downward body weight or foot pressure on the brace to crack the nuts loose. It is strictly prohibited to exert heavy force on wheel nuts once the vehicle is off the ground, as this may dislodge the car from the jack.

• Phase 3: Jacking and Wheel Removal

  • Position the jack under the dedicated chassis jacking point on the affected side (typically 20 cm behind the front wheel arch or 20 cm ahead of the rear wheel arch), marked by a notch or reinforced metal plate.

  • Rotate the jack handle clockwise until the tyre clears the ground by approximately 2-3 cm. Remove all wheel nuts, grip the tyre firmly, and pull it horizontally off the hub.

• Phase 4: Spare Wheel Installation and Lowering

  • Align the spare wheel with the hub studs and slide it on. Thread the wheel nuts by hand until finger-tight to prevent cross-threading, then snug them down evenly in a diagonal pattern over 2 to 3 stages.

  • Turn the jack handle counter-clockwise to lower the car completely to the ground. Use the wheel brace to torque the nuts to specification in a criss-cross pattern. Recommended torque ratings vary across models: roughly 90-110 N·m for passenger cars and 120-140 N·m for SUVs. As this exceeds normal arm strength, use deliberate body weight on the end of the brace (lever arm around 40-50 cm) to ensure adequate tightness.

4. Key Precautions and Risk Mitigation

• Avoid Incorrect Jacking Points: Never place the jack beneath the engine oil sump, gearbox casing, or suspension lower arms, as this causes severe structural damage. The boot floor and thin outer side skirts must never be used as load-bearing lift points.

• Strict No Under-Car Entry Rule: A vehicle supported purely by a mechanical emergency jack provides minimal stability. It is strictly forbidden to place any part of your body underneath the vehicle. If undercarriage inspection is required, heavy-duty jack stands must be used.

• Spare Tyre Pressure Verification: Space-saver tyres stored long-term lose pressure over time; factory inflation is typically set high at 420 kPa (around 4.2 bar / 60 psi), well above standard road tyres. Check and adjust the pressure to the vehicle's recommended specs (found on the driver's door B-pillar placard) before driving. Running an improperly inflated space-saver accelerates centre tread wear, severely compromises grip, and drastically extends braking distances.

• Investigating Blowout Causes: A shredded tyre sidewall generally indicates driving while severely under-inflated, pointing to a pre-existing slow leak. Following tyre replacement, inspect the opposite tyre on the same axle and its tyre valve as soon as possible.

5. Professional Roadside Assistance vs. DIY Replacement

Attempting DIY tyre replacement on expressways and inside tunnels is prohibited; always call for professional roadside assistance. In severe weather or poor nighttime visibility, engage roadside rescue teams to avoid pedestrian collision hazards caused by compromised sightlines.

6. Future Trends

• Proliferation of Run-Flat Tyres (RFT): Factory-fitted Run-Flat Tyres on marques such as BMW and Mercedes-Benz allow vehicles to travel for 80-150 km at speeds up to 80 km/h after total pressure loss, completely bypassing the hazards of roadside tyre changes on expressways.

• Tyre Sealant Kits Replacing Spare Tyres: Numerous EV and hybrid models have omitted spare wheels to save kerb weight and increase driving range, equipping tyre sealant kits instead. The procedure involves: extracting the puncture object → injecting sealant liquid → inflating to recommended pressure via the 12V compressor → driving a short distance to distribute the sealant across the inner liner. This method is only effective for tread punctures up to 6 mm; it cannot seal sidewall splits or cuts exceeding 2 cm.

• Smart TPMS Diagnostics: Advanced TPMS featuring individual four-wheel live readouts provides early warnings for slow punctures. Selected connected vehicle models now support over-the-air (OTA) service prompts and automatically locate nearby tyre shops via GPS, evolving tyre rescue from reactive emergency handling into proactive predictive maintenance.