As a general rule, never repair tyres with:
- Damage caused by being run flat or underinflated
- Injuries beyond recommended limits ( max 6 mm)
- Broken or deformed bead wires.
- Broken or separated belts
- Ruptures, creases, or detachment radial plies
- Separation or creases of rubber or fabrics
- Damage by hydrocarbons or corrosive substances.
- Liner separations too large for repair
- Loose or broken radial body cables on inside shoulder
- Soft mushy rubber on inside shoulder
- Damage beyond repair limits (see below in repair permissible limits)
To repair tyres with any one of the above conditions would result in a tyre that would not be safe for further use.
Diagram below shows repairable & non repairable area
Only T-T is the repairable area for passenger tyres. The sidewall area can be repaired in truck tyres.
Never conduct the repair under these conditions:
Repair tyres with a tread puncture larger than 1/4” (6mm).
NEVER repair tyres worn beyond the tyre’s tread wear indicators
NEVER perform a tyre repair without removing the tyre from the rim/wheel assembly for internal inspection. (Do not perform an outside-in tyre repair or on-the-wheel repair). It is essential that only a specially trained
person remove any tyre from the wheel when it has been damaged or is losing air. A thorough inspection for any internal damage can then be made.
Requirements for repair of tyres
- Every nail hole repair must have a patch inside the tyre – A mushroom patch must be used
- Patches should never overlap
- Patches always should be aligned with their bead arrows pointing to the beads (truck tyres)
- Any repair outside the crown area is section repair (only for truck tyres)
Do not make repairs where the injury damage extends into the shoulder/belt edge or where the injury extends at an angle into the shoulder area.
Temporary repair norms
- Stem or Plug or String type repairs done on a mounted wheel are considered as not proper/ reliable repairs as these could cause further damage to the tyre without inspecting the tyre throughly from inside.
- If at all a stem or plug or string type of repair needs to be carried out on a mounted wheel, it must be done purely as a temporary measure for the driver to reach the nearest repair facility for a through/proper inspection and repair of the tyre.
Repair permissible limits
- Repair is permitted only for 6mm
- Maximum number of nail holes repair per tyre is limited to two per tyre and these must be separated by at least 15 cms.
- The puncture is not repairable if there is the tyre is worn below 1.6mm tread depth overall on any 2 adjacent tread grooves.
- NEVER use only a plug (stem) or never use only a patch to repair a puncture. The injury must be completely filled with a suitable vulcanizing material or rubber stem and a patch must be applied to the inner liner to prevent air loss.
- NEVER repair a tyre that has an existing, improper repair – the tyre must be scrapped.
- NEVER substitute an inner tube for a proper repair or to remedy an improper repair in a tubeless tyre.
- NEVER do excessive spreading of the tyre or tyre beads
- NEVER buff the tyre inner liner too deep, exposing the tyre casing body (ply) cords. If this type of damage occurs during buffing, the tyre must be scrapped.