Tyre Repair

Definition and Core Role

Tyre repair refers to the process of restoring airtightness by sealing puncture holes via physical or chemical methods after a tyre is penetrated by foreign objects (such as nails, screws, or metal debris). Its fundamental purpose is "baseline safety": proper professional repair can salvage a punctured tyre that would otherwise be scrapped, effectively lowering vehicle running costs. However, any repair compromises the structural integrity of the tyre, meaning tyre repairs are subject to strict performance limits and safety thresholds.

Common Tyre Repair Methods

Depending on the repair technique, the following solutions are commonly available in the market: 

Internal Patch Repair 

Principle: Buff the inner liner of the damaged area, apply vulcanising cement, and adhere a rubber patch. 

Characteristics: Cost-effective and straightforward. However, it only seals the inner airtight liner without filling the puncture channel; the exposed outer hole leaves internal steel belts vulnerable to moisture, oxidation, and rust. 

Tyre String Plug Repair (External Plug / "Cacing") 

Principle: Insert a vulcanised rubber strip directly into the puncture hole from the outside of the tyre.

Characteristics: Highly convenient as it requires no tyre demounting. However, it remains unstable under hard driving conditions and is prone to secondary leaks. It should strictly serve as a temporary emergency fix rather than a permanent solution. 

Combination Mushroom Plug Repair

Principle: Insert a mushroom-shaped rubber stem from the inside out through the puncture channel, where the integrated stem seals the hole and the patch cap bonds flush with the inner liner.

Characteristics: Widely recognised as the best and most reliable tyre repair method. It seals the inner airtight liner while completely filling the puncture channel, preventing water ingress and belt corrosion. 

Hot Vulcanisation (Hot Patch Repair)

Principle: Bond the repair rubber compound seamlessly with the original tyre casing using specialised heating equipment.

Characteristics: Delivers an exceptionally durable fix. However, because curing temperatures are difficult to regulate precisely, improper execution can easily compromise the tyre's rubber compound. It is rarely used for passenger vehicles today.

Tyre Repair Safety Red Lines (Conditions Requiring Scrapping)

Not all punctures can be repaired. If any of the following scenarios occur, the tyre must be replaced immediately, and repair is strictly prohibited: 

Sidewall damage: The sidewall is the thinnest and most dynamically stressed section of a tyre, undergoing the most severe flexing during driving. Any sidewall damage (even a superficial cut exposing the cord plies) carries an extremely high blowout risk. 

Oversized puncture: The puncture hole diameter exceeds 6 mm. 

Clustered or repeated punctures: If punctures are concentrated in a tight area, or if the tyre has already undergone multiple previous repairs (typically more than 3 times), its structural integrity is severely compromised.

Rubber ageing or cracking: If the tyre exhibits severe dry rot, surface cracking, or rubber degradation, patch bonding will be compromised and the casing can no longer safely sustain repairs. 

Standard Procedure and Key Technical Points

Mandatory wheel balancing: Regardless of the repair method used, the tyre's mass distribution changes. Wheel balancing must be performed after repair; otherwise, high-speed vibrations will accelerate wear on the suspension components.

Thorough cleaning and buffing: Foreign objects must be completely removed from the puncture site, and the inner liner must be properly buffed using professional tools; otherwise, the patch can easily debond.

Airtightness test: Once repaired and reinflated, soapy water must be sprayed thoroughly over the repair area to check for micro-bubbles and ensure a 100% airtight seal.

Motorist Guide to Avoiding Common Pitfalls

Avoid aggressive hole reaming: Inexperienced workshops often forcefully enlarge puncture holes to fit repair tools, which tears internal cord plies and causes irreversible structural damage. 

Never drive with an embedded nail for long: An embedded nail continuously shifts and "saws" through the internal steel belts as the tyre rolls. The longer you drive on it, the worse the damage becomes, increasing the risk of the tyre being written off. 

High-speed driving precautions post-repair: A repaired tyre experiences a slight drop in thermal resistance and overall physical strength. For high-performance tyres, avoid sustained extreme high-speed driving after a repair, and regularly inspect the repair site for sidewall bulges or slow pressure loss.