How to determine the degree of wear and damage of tires

The degree of tire wear and damage is directly related to driving safety, and a systematic evaluation should be conducted through a combination of standardized testing methods and visual judgment. We provide professional solutions from four dimensions: wear identification, damage classification, detection tools, and decision logic

1、 Quantitative assessment of tire wear degree

1. Depth detection of tread grooves

statutory standards:

According to the "Technical Conditions for Safety of Motor Vehicle Operation" (GB 7258-2017) in China, the tread groove depth of passenger car tires is ≥ 1.6mm, and that of motorcycle tires is ≥ 0.8mm.

Critical value: When the groove depth is less than 1.6mm, the braking distance increases by 40% -60% in rainy weather, and the snow grip decreases by more than 70%.

Testing method:

Tool method: Use a tread depth gauge (accuracy 0.1mm) to measure 3-5 points in the main drainage channel and take the average value.

Simple method: Insert a 1 yuan coin (emblem face) into the groove. If the chrysanthemum pattern is completely visible, the groove depth should be less than 1.6mm.

2. Analysis of tread wear morphology

Suggestions for handling potential causes of wear type characteristics

The depth of the central groove on the worn tire surface is significantly lower than that on both sides. If the tire pressure is too high (>20% of the standard value), adjust the tire pressure to the standard value and replace the tire

Unilateral wear and tear on the same axle tire, with a difference in groove depth of more than 2mm on one side. Four wheel alignment misalignment (camber/toe angle deviation). Immediately perform four-wheel alignment and check the suspension system

Feather shaped worn tread pattern with jagged edges and burrs on one side. Loose suspension components or worn ball joints. Replace damaged components and replace tires in pairs

Local block like wear on the tire surface, irregular patch like wear, frequent emergency braking or abnormal braking system. Check the ABS/EBD system and replace the brake pads

2、 Grading assessment of tire damage

1. Determination of sidewall injury

Crack damage:

Microcracks: length<3mm, depth<0.5mm → can continue to be used, but requires quarterly re examination.

Penetrating crack: length ≥ 3mm or depth>1mm → replace immediately (the curtain layer has been exposed).

Cut/scratch:

Safety threshold: Tire sidewall rubber thickness ≥ 3mm (can be determined by tire sidewall protrusion markings). If the scratch depth is greater than 1/3 of the rubber thickness, X-ray inspection is required to confirm whether the cord is broken.

Bulge deformation:

Judgment criteria: Local bulging of the tire sidewall>2mm, with a sponge like sensation when pressed.

Principle: The rupture of the curtain layer leads to the accumulation of high-pressure gas inside, which may cause tire blowouts at any time.

2. Determination of tread damage

Nailing/Piercing:

Safe zone: The central area of the tire tread (distance from the tire shoulder ≥ 20mm), and the nail hole diameter<6mm → can be repaired (mushroom nail or patch process).

Danger zone: Shoulder/sidewall area, or nail holes penetrating the fabric layer → must be replaced.

Tire gnawing/uneven wear:

Abnormal wear amount: The difference in tread groove depth of a single tire is greater than 1.5mm/10000 kilometers → The deformation of the suspension system needs to be checked.

Aging and cracking:

Judgment criteria: Turtle cracks with a thickness greater than 2mm appear on the tread, and the rubber hardness is greater than Shore A85 (which can be tested by a hardness tester).

Aging cycle: In areas where the ambient temperature is above 35 ℃, the aging rate of tires increases by 30% after 5 years.

3、 Professional testing tools and operating procedures

1. Basic testing tools

Tool name, purpose, accuracy requirements, usage scenario

Tire tread depth gauge measures groove depth with an accuracy of 0.1mm. Daily self inspection/routine inspection by repair shop

Tire pressure gauge checks whether the tire pressure meets the standard ± 0.02 bar, with an error range of monthly testing (in cold tire condition)

Tire Hardness Tester Evaluation of Rubber Aging Degree Shore A Hardness Tester Special Testing for Tires Over 5 Years

Endoscopic examination of the inner curtain of the tire sidewall with a fiber diameter of ≤ 3mm and a lens that can rotate 180 ° for suspected bulges/deep injuries

2. Professional testing process

Appearance pre inspection:

Check for foreign objects embedded in the tire surface (such as stones larger than 3mm that need to be removed).

Record the sidewall production date (the last 4 digits of the DOT code, such as "3521" indicating the 35th week of production in 2021).

Dynamic detection:

Is there any abnormal shaking during driving (excluding wheel hub deformation).

Is there any deviation during braking (reflecting differences in tire grip).

Laboratory testing (optional):

X-ray inspection: detect the breakage rate of the curtain wire (>5% needs to be replaced).

Thermal imaging analysis: Evaluate the uniformity of tire surface temperature distribution (temperature difference>15 ℃ indicates internal structural abnormalities).

4、 Decision logic and risk classification

1. Classification of wear/damage levels

Classification criteria, disposal suggestions, risk level

The depth of the first level ditch is 1.6-2.5mm, and there is no structural damage, so it can continue to be used. It is recommended to recheck after 6 months

The depth of the secondary ditch is 1.0-1.6mm, or there may be micro cracks/single nail speed limit driving (≤ 80km/h), to avoid high-speed/heavy loads

If the depth of the third level groove is less than 1.0mm, or if the sidewall crack is greater than 3mm/bulging/multiple nailing, it should be replaced immediately. It is prohibited to drive on highways

Grade 4 service life>8 years, or rubber hardness>Shore A90, mandatory scrapping, even if the appearance is intact and extremely high

2. Example of scenario based decision-making

Case 1: The tread groove of a taxi is 1.8mm deep, but there are 2mm scratches on the sidewall

▶  Decision: Level 2 risk, limit driving speed and inspect scratch extension every week, replace within 3 months.

Case 2: A household SUV has a single-sided tire groove depth ratio that is 2.5mm shallower than the side, and the tire pressure is normal

▶  Decision: Level 2 risk, immediately perform four-wheel alignment. If the alignment parameters are normal, check the fatigue level of the suspension spring.

Case 3: The tire was produced in the 12th week of 2018, with a groove depth of 2.2mm but a hardened and shiny surface

▶  Decision: Level 3 risk, rubber aging leads to decreased impact resistance, it is recommended to replace immediately.

5、 User self inspection and prevention suggestions

1. Daily mandatory inspection items

Tire pressure monitoring:

In the cold tire state, the standard tire pressure value can be found on the door frame label (such as 2.3 bar), with an error range of ± 0.1 bar.

Abnormal tire pressure impact:

▶  Tire pressure drops by 10% → Fuel consumption increases by 1.5%, tread wear accelerates by 20%

▶  Tire pressure increases by 10% → central wear intensifies, comfort decreases by 30%

Cleaning of foreign objects:

Use a screwdriver to remove the stones embedded in the tread (focus on cleaning the main groove).

2. Monthly mandatory inspection items

Alignment of wear marks:

If the "Δ" or "TWI" raised mark in the tread drainage groove is flush with the tread, it must be replaced.

Tire sidewall injury scan:

Use a mobile phone flash to tilt the sidewall and observe for any abnormal shadows (possibly due to internal cord breakage).

3. Preventive maintenance

Regular rotation:

The front wheel drive vehicle performs a crossover every 10000 kilometers (left front) ↔ Right rear, right front ↔ Left rear), the rear wheel drive car changes direction in the same direction.

Dynamic balance correction:

After replacing or repairing the tire, the dynamic balance error should be controlled within ≤ 5g (otherwise the high-speed steering wheel will shake).

Four wheel positioning:

Check once a year or 20000 kilometers, with key parameters:

▶  Front wheel camber angle: -0.5 °~1.5 °

▶  Front wheel toe angle: 0 °± 5 '

Suggestion:

Establish a tire lifecycle file and record the following data:

Production date, installation date, first inflation date

Ditch depth data for each inspection (at least 3 measurement points)

Damage location and repair records

History of four-wheel alignment parameters

When the tire meets the following conditions simultaneously, it must be replaced:

▶  Service life ≥ 5 years and (safety red line)

▶  Tread groove depth<2mm or (performance red line)

▶  Structural damage or (safety red line) on the sidewall of the tire

▶  Rolling resistance coefficient increases by more than 20% compared to the factory value (energy consumption red line)

Attention: For scenarios with strict safety requirements (such as buses with more than 7 seats and hazardous chemical transport vehicles), it is recommended to adopt "double red line control" - that is, when the tread groove depth approaches 1.6mm or the service life approaches 5 years, the replacement procedure should be immediately initiated to avoid risk accumulation due to detection errors.