Guidance

Tyre defects and damage: HGVs, buses and trailers

Published 9 December 2020

Applies to England, Scotland and Wales

You can use this guide if you’re a vehicle operator or maintenance inspector to help you make consistent decisions about tyre wear, defects and damage.

This should:

  • improve the safety of vehicles
  • reduce the time spent contesting borderline cases
  • reduce the number of roadworthy tyres that are replaced prematurely

1. Tyre inspection equipment

Use a blunt probe for all inspections.

Do not use a sharp-end probe - this can cause further damage to the tyre during the inspection.

Tyre probe

Only use a blunt probe for inspections.

2. Irregular tread wear

2.1 Summary of legal requirements

Minimum tread depth 1mm (vehicle over 3,500kg gross vehicle weight) over a continuous band covering at least any three-quarters of the breadth of the tread around the entire circumference.

The base of any groove of the original tread pattern must be visible on the remaining one-quarter of the tread.

‘Breadth of tread’

‘Breadth of tread’ means the part of the tyre in contact with the road, under normal use and measured across the tyre.

‘Original tread pattern’

The ‘original tread pattern’ means:

  • the tread pattern immediately after the tyre was retreaded (for retreaded tyres)
  • the manufacturers’ recut tread pattern (for wholly recut tyres)
  • the manufacturers’ recut tread pattern on the part that has been recut, and the tread pattern of the tyre when it was new on the other part (for partially recut tyres)
  • the tread pattern of the tyre when it was new (for any other tyre)

These things are excluded from the term ‘original tread pattern’:

  • grooves which wear out before the main grooves are worn
  • minor features such as sipes (small slots that are cut or moulded into the tread surface), small extensions to the circumferential grooves and minor lateral grooving on shoulders

2.2 Irregular tread wear, more than 1mm tread depth over more than three-quarters of the tread area

Irregular tread wear, more than 1mm tread depth over more than three-quarters of the tread area

Roadside inspection

Inspection Notice

MOT (annual test)

Pass (advise at discretion of assessor).

Reason

Depth of tread is greater than 1mm throughout the circumference of a band covering at least three-quarters of the tread width & the base of any groove of the original tread pattern is visible on the remaining one-quarter of the tread

2.3 Irregular tread wear, less than 1mm tread depth over less than three-quarters of the tread area

Irregular tread wear, less than 1mm tread depth over less than three-quarters of the tread area

Roadside inspection

Immediate Prohibition

MOT (annual test)

Fail - Dangerous* - Tyre tread worn below the legal minimum on any tyre fitted to a steered axle and/or 50% or more of the total number of tyres fitted to non-steered axles.

Reason

  1. Remaining legal tread pattern covers less than three-quarters of the tread width.
  2. The base of any groove of the original tread pattern is not visible on the remaining one-quarter of the tread.

2.4 Flat spot, less than 1mm tread across three-quarters of the tyre tread, and exposed cords in the tread area

Flat spot, less than 1mm tread across three-quarters of the tyre tread and exposed cords in the tread area

Roadside inspection

Immediate Prohibition

MOT (annual test)

Fail for tread Dangerous* - Tyre tread worn below the legal minimum on any tyre fitted to a steered axle and/or 50% or more of the total number of tyres fitted to non-steered axles.

Fail for cord exposed. (Dangerous* - PG9 may be issued if failure of the tyre is likely)

Reason

  1. Cords exposed.
  2. Depth of tread is not greater than 1mm throughout the circumference of a band covering at least three-quarters of the tread width.
  3. The base groove of the original tread pattern is not visible on the remaining one-quarter of the tread.

3. Sidewall abrasion

3.1 Tyre markings

A tyre will need to display markings indicating it is suitable for the application, nominal size, load index/ply rating, speed rating and tyre age code.

Tyre marking diagram
  1. Tyre Section width.
  2. Aspect ratio.
  3. Construction (R=radial).
  4. Rim diameter (inches).
  5. Load Index (single tyre).
  6. Load Index (dual mounted).
  7. Speed symbol.
  8. Additional service description / Unique point.
  9. Location of tread wear indicator.
  10. Approval numbers.
  11. Manufacturing date code.
  12. DOT manufacturing site code.
  13. Regroovable tyre.
  14. Data not applicable to European markets.

3.2 Sidewall heavily abraded with regulatory date markings illegible, no cords visible, overheating or other damage evident

Sidewall heavily abraded with regulatory markings illegible, no cords visible, overheating or other damage evident

Roadside inspection

Front steered axle or any single wheels fitted to a minibus - Delayed prohibition.

Any other position - inspection notice.

MOT (annual test)

Front steered axle or any single wheels fitted to a minibus - Fail major defect.

Fitted to any other position - Pass minor defect.

Reason

Where regulatory date makings are not visible on at least one sidewall, a check will be made on the opposing sidewall. A check will be made visually for evidence of deterioration.

Where there is clear evidence of tyre deterioration, the roadside inspection would be increased to an immediate prohibition action for front-steered axles and any single wheels fitted to a minibus.

3.3 Body cords exposed on the sidewall

Body cords exposed on the sidewall

Roadside inspection

Immediate prohibition.

MOT (annual test):

Fail (Dangerous* - PG9 may be issued if failure of the tyre is likely)

Reason

Body cords visible/damaged.

4. Damage

4.1 Summary of legal requirements

The cords must not be visible. This applies to any type or size of wear or damage condition, examined with or without the use of a blunt probe.

Where damage or cuts are larger than 25mm or 10% of the section width (whichever is the greater), the cords must not be detectable on examination with a blunt probe.

Sections of tread must not be partially separated from the tyre.

Any sidewall bulges must not be spongy or easy to depress.

Use this criteria when you assess a cut in a tyre:

  • any ply or cord that can be seen without touching the tyre would be an MOT (annual test) fail or prohibition action at a roadside inspection
  • any exposed ply or cord that can be seen (irrespective of the size of the cut) when you fold back the rubber or open a cut with a blunt instrument (so you do not cause further damage), would also be a deficiency
  • if a cut which is more than 25mm or 10% of the section width (whichever is the greater), is opened with a blunt instrument and cords can be felt but not seen, this would be a deficiency (make sure it is the cords that you feel and not a foreign object)

Cuts which are deep enough to reach the cords or ply but are less than 25mm or 10% of the section width (whichever is the greater), and have not damaged or exposed the cords or ply do not breach the legal requirements for tyres.

4.2 Tread separation

Tread separation

Roadside inspection

Immediate prohibition.

MOT (annual test)

Fail (Dangerous- PG9 issued).

Reason

Section of tread partially separated: risk of rubber detachment.

4.3 A cut less than 25mm to the tread area and less than 10% of the section width, with no cords damaged or exposed

A 25mm cut to tread area and less than 10% of the section width, with no cords damaged or exposed

Roadside inspection

With the use of blunt probe. Unable to detect cords; Pass.

MOT (annual test)

With a blunt probe unable to detect cords; Pass.

Reason

Cuts which are not deep enough to reach the cords or ply but are less than 25mm or 10% of the section width, whichever is the greater do not breach the legal requirements for tyres.

4.4 Cut to tread exposing cords

Cut to tread exposing cords

Roadside inspection

Cords visible; Immediate prohibition.

MOT (annual test)

Fail (Dangerous* - PG9 may be issued if failure of the tyre is likely).

Reason

Cords visible in tread area.

4.5 Tyre tread cut to create a rubber flap exposing cords

Tyre tread cut to create a rubber flap exposing cords

Roadside inspection

Cords exposed and visible in tread area; Immediate Prohibition.

MOT (annual test)

Fail (Dangerous* PG9 may be issued if failure of the tyre is likely).

Reason

Cords visible in tread area.

4.6 Tyre regrooved too deep

Tyre regrooved too deep

Roadside inspection

Cords exposed; Immediate Prohibition

MOT (annual test)

Fail (Dangerous* PG9 may be issued if failure of the tyre is likely)

Reason

Cords visible in tread area.

4.7 Bulge in sidewall is easy to depress (spongy)

Bulge in sidewall is easy to depress (spongy)

Roadside inspection

Tyre bulging caused separation or partial failure of its structure; Immediate Prohibition.

MOT (annual test)

Fail (Dangerous – PG9 issued)

Reason

Casing separation.

4.8 Minor crazing (fine cracks) on the sidewall, but with no cords exposed

Minor crazing (fine cracks) on the sidewall, but with no cords exposed

Roadside inspection

Pass.

MOT (annual test)

Pass.

4.9 Minor cracking in grooves, no cords exposed

Minor cracking in grooves, no cords exposed

Roadside inspection;

Pass.

MOT (annual test)

Pass.

4.10 Tyre age code 3307 fitted to HGV front-steered axle

Tyre age code 3307 fitted to HGV front-steered axle

Roadside inspection

Tyre age more than 10 years old: Immediate Prohibition.

MOT (annual test)

Tyre age more than 10 years old: Fail Dangerous PG9 Issued.

Tyre age code manufactured week 33 of year 2007. Tyre age code must be present.

Tyres more than 10 years old shall not be fitted to front steered axle/s and any single wheel configuration on a minibus. If it’s a retreaded tyre, check the retreading tyre age code.

4.11 Incorrect tyre regroove pattern

Incorrect tyre regroove pattern

Roadside inspection

Tyre regroove pattern incorrect; Inspection Notice.

MOT (annual test)

A wholly or partly recut tread pattern is not to the manufacturers recut tread pattern; Fail Major.