Tire Inspection and Tread Depth Guidelines: Complete Technical Guide

Tires are the only point of contact between a vehicle and the road. Proper tire inspection identifies safety hazards before they cause accidents, prevents premature wear through early detection of alignment issues, and ensures customers receive appropriate service recommendations based on measurable standards.

This comprehensive guide covers tire tread depth measurement, wear pattern diagnosis, age verification, sidewall damage assessment, and replacement criteria used by professional technicians nationwide.

Why Tire Inspection Standards Matter
Tread Depth Standards and Legal Minimums
Proper Tread Depth Measurement Technique
Tire Wear Pattern Diagnosis
Tire Age and DOT Date Code Verification
Sidewall Damage Assessment
Tire Pressure Guidelines
State and Federal Tire Regulations
When to Replace vs. Repair Tires
Common Tire Inspection Mistakes

Why Tire Inspection Standards Matter

Safety Impact

According to NHTSA data, tire-related crashes cause hundreds of fatalities annually. Proper tire inspection prevents:

Blowouts from worn tread, age deterioration, or sidewall damage
Loss of vehicle control from inadequate tread depth in wet conditions
Hydroplaning when tread depth falls below 4/32"
Extended stopping distances — tires at 2/32" increase wet braking distance by 30-50%

Legal Compliance

All 50 states regulate minimum tire tread depth:

Most states: 2/32" legal minimum in two adjacent tread grooves
Commercial vehicles (Federal): Steer tires 4/32" minimum, others 2/32" minimum
Inspection rejection: Exposed cords, bulges, or tread below legal minimum

Financial Protection for Shops

Systematic tire inspection with measurements and photos provides:

Defensible recommendations based on measurable standards (not subjective judgment)
Documentation that protects against "you said I needed tires" disputes
Revenue recovery by identifying legitimate needs (alignment issues from uneven wear, age-related replacement)

Real Example: Customer's front tires measure 4/32" inner edge, 7/32" outer edge. Without measuring both edges, the shop misses:

The alignment issue causing uneven wear
The fact that tires are approaching minimum despite appearing adequate on outer edge
The opportunity to recommend alignment service along with tire replacement (prevents new tires from wearing same way)

Tread Depth Standards and Legal Minimums

Federal and State Requirements

Legal Minimum (Most States):

2/32" (1.6mm) in any two adjacent tread grooves

Commercial Vehicle Federal Standards (49 CFR 393.75):

Steer axle tires: 4/32" (3.2mm) minimum
All other tires: 2/32" (1.6mm) minimum

Key Principle: Legal minimum is the absolute failure point, not the service point. Professional shops should recommend replacement BEFORE tires reach legal minimum.

Recommended Replacement Thresholds

All-Season Tires:

Recommended replacement: 4/32" (3.2mm)
Rationale: Wet traction significantly degrades below 4/32"; hydroplaning risk increases

Winter/Snow Tires:

Recommended replacement: 6/32" (4.8mm)
Rationale: Snow traction depends on deep tread grooves; insufficient below 6/32"

Performance Tires:

Recommended replacement: 3/32" (2.4mm)
Rationale: Performance tires prioritize dry grip over wet traction; may wear faster

New Tire Tread Depth (Reference):

Passenger car tires: 10/32" to 12/32" (8-10mm)
Truck/SUV tires: 12/32" to 15/32" (10-12mm)

The 4/32" Standard Explained

Why 4/32" instead of legal 2/32"?

Research shows that wet braking distance increases significantly below 4/32":

8/32" tread (new-ish tire): Baseline braking distance
4/32" tread: ~15% increase in wet stopping distance
2/32" tread (legal minimum): ~30-50% increase in wet stopping distance

Translation: A vehicle that stops in 150 feet with new tires requires 200+ feet at legal minimum — an extra 50 feet is the difference between avoiding an accident and a collision.

Proper Tread Depth Measurement Technique

Tools Required

Digital Tread Depth Gauge (Recommended):

Range: 0-25/32" (0-20mm)
Accuracy: ±0.5/32" (±0.4mm)
Displays reading in 32nds of an inch or millimeters
Cost: $15-30

Analog Tread Depth Gauge:

Mechanical gauge with sliding probe
Less precise but adequate
Cost: $5-15

Penny Test (Quick Field Check - NOT for documentation):

Insert penny with Lincoln's head upside down into tread groove
If top of Lincoln's head visible = ≤2/32" (at legal minimum — replace immediately)
If Lincoln's head partially covered = 3-4/32" (replace soon)
Important: This is a quick check only — use gauge for actual measurements

Step-by-Step Measurement Procedure

1. Measure All Four Tires

Never measure only the front tires. Rear tire failure is just as dangerous as front tire failure.

2. Measure THREE Points Across Tire Width

For each tire, measure:

Inner edge (closest to vehicle center)
Center tread groove
Outer edge (closest to outside of vehicle)

Why? Uneven wear patterns (edge wear, center wear) are only visible by measuring multiple points. A tire may measure 7/32" in the center but 2/32" on the inner edge — measuring center only would miss impending failure.

3. Measure Multiple Locations Around Circumference

Measure at least 3 points around tire circumference (minimum, maximum, and middle):

Tires can wear unevenly around circumference (flat spots from hard braking, cupping from worn shocks)
Always record the minimum depth (thinnest measurement)

4. Insert Gauge Properly

Place gauge probe into tread groove (valley between tread blocks)
Press down until gauge base contacts tread surface
Ensure probe reaches tread bottom (not resting on stone or debris in groove)
Read measurement in 32nds of an inch

5. Document All Measurements

Record format example:

RF (Right Front): Inner 4/32" | Center 6/32" | Outer 5/32" → MIN: 4/32"
RR (Right Rear):  Inner 6/32" | Center 7/32" | Outer 6/32" → MIN: 6/32"
LF (Left Front):  Inner 3/32" | Center 6/32" | Outer 5/32" → MIN: 3/32"
LR (Left Rear):   Inner 6/32" | Center 7/32" | Outer 6/32" → MIN: 6/32"

Analysis from this example:

Front tires showing inner edge wear (3-4/32" inner vs. 5-6/32" outer)
Indicates negative camber or toe-out alignment issue
Front tires approaching replacement threshold (4/32")
Recommendation: Replace front tires + 4-wheel alignment to prevent new tires from wearing same way

Tire Wear Pattern Diagnosis

Uneven tire wear reveals alignment issues, suspension problems, and improper inflation — identifying these patterns prevents premature replacement tire wear.

Normal Wear

Appearance: Even wear across entire tread width and circumference

Measurements:

Inner, center, and outer tread depths within 1/32" of each other
Wear consistent around tire circumference

Indicates: Proper inflation, good alignment, functional suspension

Action: None needed — continue monitoring

Center Wear (Center More Worn Than Edges)

Appearance: Center tread ribs visibly lower than shoulder (edge) ribs

Measurements:

Center: 4/32"
Inner edge: 7/32"
Outer edge: 7/32"
3/32" difference = significant center wear

Cause: Chronic over-inflation

Mechanism:

Excessive tire pressure causes tire to bulge in center
Center tread carries more weight than edges
Center wears faster than edges

Verification: Check tire pressure history — typically inflated 5-10 PSI over specification consistently

Example:

Vehicle spec: 32 PSI
Customer consistently inflates to 40-42 PSI (believing "harder is better")
Result: Tires last 30,000 miles instead of 50,000+ miles

Prevention: Educate customer on proper tire pressure; recommend checking monthly using door placard specification

Edge Wear (Both Edges More Worn Than Center)

Appearance: Both inner and outer edges visibly more worn than center tread

Measurements:

Inner edge: 3/32"
Center: 6/32"
Outer edge: 3/32"
3/32" difference = significant edge wear

Cause: Chronic under-inflation

Mechanism:

Low tire pressure causes tire to sag
More weight transfers to outer edges
Edges wear faster than center

Verification: Check tire pressure — typically 5-10 PSI below specification consistently

Additional Consequences of Under-Inflation:

Increased heat buildup (can cause blowout)
Reduced fuel economy (3-5% loss per 10 PSI under-inflation)
Premature sidewall cracking from excessive flexing

Prevention: Check tire pressure monthly; consider TPMS if not equipped

Inner Edge Wear (One Edge Significantly More Worn)

Appearance: Inner edge (toward vehicle center) worn significantly more than outer edge

Measurements:

Inner edge: 2/32"
Center: 5/32"
Outer edge: 6/32"
4/32" difference = severe inner edge wear

Cause: Negative camber (wheel tilts inward at top) or toe-out

Mechanism:

Wheel angle causes inner edge to contact road more heavily
Inner edge bears more weight and scrubs more during driving
Accelerated inner edge wear

Common On:

Vehicles with independent rear suspension
Worn control arm bushings allowing excessive camber
Lowered vehicles with improper alignment correction

Verification:

Measure inner vs. outer tread depth (>2/32" difference confirms)
Visual alignment check — look at front wheels from front of vehicle; if tops lean inward, negative camber present

Action:

4-wheel alignment required
Replace control arm bushings if worn
If alignment cannot be brought to spec, camber adjustment or suspension components may need replacement

Outer Edge Wear

Appearance: Outer edge (away from vehicle center) worn significantly more than inner edge

Measurements:

Inner edge: 6/32"
Center: 5/32"
Outer edge: 2/32"
4/32" difference = severe outer edge wear

Cause: Positive camber (wheel tilts outward at top) or aggressive cornering

Mechanism:

Positive camber or hard cornering puts more weight on outer edge
Outer edge bears more stress and wears faster

Common On:

Performance vehicles driven aggressively
Worn suspension components (ball joints, control arms)
Heavy loads causing suspension sag

Action:

Alignment correction
Inspect and replace worn suspension components
Counsel customer on driving style impact if aggressive cornering is cause

Cupping or Scalloping (Wavy Wear Pattern)

Appearance: Tread surface has high and low spots creating wavy pattern around tire circumference

Physical Test: Run hand across tread — feels like waves with high spots and low spots every 3-4 inches

Measurements:

Tread depth varies by 2-3/32" around tire circumference
Creates rhythmic pattern of wear

Cause:

Worn shocks or struts allowing tire to bounce as it rolls
Out-of-balance tires causing vibration and uneven contact
Bent wheel causing tire to wobble

Mechanism:

Tire bounces (from worn shock) or vibrates (from imbalance)
Uneven contact creates high-wear spots where tire slaps pavement
Low-wear spots where tire rebounds

Symptoms:

Humming or roaring noise while driving (cupped tread creates noise)
Vibration at highway speeds
Poor ride quality

Common On:

Vehicles with shocks/struts >80,000 miles without replacement
Vehicles with chronic tire imbalance issues

Action:

Replace worn shocks/struts
Balance tires (if imbalance is cause)
Check for bent wheels
Important: Cupping damage is permanent — even after fixing cause, cupped tires will continue to make noise until replaced

Feathering (One-Sided Tread Block Wear)

Appearance: Individual tread blocks worn at an angle — sharp edge on one side, rounded edge on other

Physical Test: Run hand across tread:

Smooth in one direction
Sharp/fuzzy/grabby in opposite direction

Cause: Toe misalignment (wheels pointed in or out instead of straight ahead)

Mechanism:

Wheel pointing slightly in (toe-in) or out (toe-out) causes tire to scrub sideways as it rolls
Tread blocks wear at angle from scrubbing action
Creates feathered appearance

Most Sensitive To: Even 1/8" total toe misalignment can cause feathering in 5,000-10,000 miles

Common After:

Hitting potholes or curbs (jolts suspension out of alignment)
Replacing suspension components without alignment
Any front-end work (tie rods, control arms, etc.)

Action:

4-wheel alignment mandatory
Toe is easiest adjustment but most critical for tire wear
Recommend alignment after any suspension work or impact

Flat Spots

Appearance: Localized flat areas on tread surface — tire not round

Cause:

Hard braking with wheels locked (no ABS or ABS failure)
Vehicle parked long-term without moving (6+ months)
Towing with wheels on ground (non-driven axle)

Mechanism:

Locked wheel slides on pavement, grinding flat spot on tread
Long-term parking causes tire to develop flat spot from weight (usually temporary, may recover after driving)

Symptoms:

Thumping noise at low speeds
Vibration that may diminish after warming up (if from parking)

Action:

Severe flat spots from braking = replace tire (permanent damage)
Flat spots from parking = drive vehicle; if spot doesn't round out after 10-20 miles, replace tire

Tire Age and DOT Date Code Verification

Tires degrade from age even with adequate tread depth. Rubber oxidizes, UV exposure causes cracking, and internal structure weakens over time.

Industry Standards for Tire Age

Tire Industry Association (TIA) & Rubber Manufacturers Association (RMA) Recommendations:

6 years in service: Inspect annually for deterioration
10 years from manufacture date: Replace regardless of appearance or tread depth

Most Tire Manufacturers:

Replace at 6 years in service (from installation date)
Absolute maximum 10 years from manufacture date

Why Age Matters:

Rubber compounds degrade from oxidation, ozone, and UV exposure
Internal cords weaken even without visible external damage
Blowout risk increases dramatically after 6 years regardless of tread depth

How to Read DOT Date Codes

DOT Code Location:

Stamped on tire sidewall near rim
Usually on inner sidewall (away from curb when mounted)
May need to turn steering wheel or lift vehicle to see

DOT Code Format:

DOT XX XX XXX WWYY
            ↑↑ ↑↑
            WW = Week of manufacture (01-52)
            YY = Year of manufacture

Example:

DOT code ends in "1422"
WW = 14 (14th week of the year)
YY = 22 (year 2022)
Translation: Manufactured in April 2022 (14th week = early April)

Current date: December 2025 Tire age: 3 years, 8 months old Status: Good (under 6-year service life)

DOT Date Code Examples

DOT Code Ending	Week	Year	Manufacture Date	Age (Dec 2025)	Status
0824	08	2024	February 2024	1 year 10 months	✓ Good
2021	20	2021	May 2021	4 years 7 months	✓ Good
3619	36	2019	September 2019	6 years 3 months	⚠ Inspect annually
1516	15	2016	April 2016	9 years 8 months	⚠ Replace soon
0213	02	2013	January 2013	12 years 11 months	⛔ Replace immediately
418	41	2018	October 2018	7 years 2 months	⚠ Plan replacement

CRITICAL WARNING: Tires with only 3-digit date codes (pre-2000 format) are over 25 years old — replace immediately, do not drive.

Visual Signs of Tire Aging (Dry Rot)

Even with adequate tread depth, aged tires show deterioration:

Early Stage (5-7 years):

Fine surface cracks in sidewall rubber
Slight discoloration or fading of sidewall lettering
Rubber feels slightly harder when pressed

Moderate Stage (7-9 years):

Deeper cracks (1-2mm depth)
Network of cracks across sidewall
Noticeable rubber hardening
Weather checking on tread blocks

Severe Stage (10+ years):

Deep cracks >3mm exposing white underlying material or cords
Chunks of rubber separating from sidewall
Extreme hardening (rubber doesn't flex when pressed)
Possible tread separation

Action Thresholds:

Fine surface cracks + tire age 5-7 years: Plan replacement within 12 months
Deep cracks 1-2mm + tire age 7-9 years: Replace within 3-6 months
Cracks >3mm or exposed cords: Replace immediately — do not drive

Sidewall Damage Assessment

Sidewall damage compromises tire structural integrity and cannot be repaired — replacement is the only option.

Types of Sidewall Damage

1. Bulges or Bubbles (ANY SIZE)

Appearance: Visible protrusion from otherwise smooth sidewall — may be small (dime-sized) or large (baseball-sized)

Cause: Impact damage (pothole, curb) breaks internal cords; air pressure pushes inner liner through damaged area

Critical Warning: Any visible bulge indicates imminent catastrophic failure — DO NOT DRIVE

Action: Replace immediately; tow vehicle if necessary

Why Dangerous:

Internal cords provide tire strength
Broken cords = zero remaining strength in that area
Can explode without warning during driving (especially highway speeds)

2. Cuts, Gashes, or Slashes

Severity Assessment:

Depth	Cord Exposure	Rating	Action
<2mm	No	Minor	Monitor; likely OK if no air loss
2-4mm	No	Moderate	Replace if concerned about safety margin
>4mm	No	Severe	Replace
Any depth	Yes	Critical	Replace immediately

Verification: Use fingernail or probe to check cut depth; if white fabric or steel cords visible = replace immediately

Important: Sidewall punctures from nails/screws CANNOT be repaired (tread punctures can be repaired)

3. Abrasions or Scuffs

Appearance: Sidewall rubber scraped or worn from curb contact

Assessment:

Surface scuff only (<1mm depth): Cosmetic damage — monitor but typically safe
Deep abrasion exposing fabric: Replace immediately

Prevention: Avoid parking too close to curbs; leave 6-12" clearance when parallel parking

4. Cracks (Dry Rot)

See "Tire Age" section above for crack assessment by depth and age.

Tire Pressure Guidelines

Why Proper Inflation Matters

Under-Inflation (Most Common):

Causes edge wear (both edges more worn than center)
Generates excessive heat (can cause blowout)
Reduces fuel economy by 3-5% per 10 PSI under-inflation
Increases stopping distance

Over-Inflation:

Causes center wear (center more worn than edges)
Reduces contact patch (less traction)
Harsher ride quality
Increased impact damage risk from potholes

How to Check Tire Pressure Correctly

Critical Rule: Check When COLD

Cold tire definition: Vehicle parked 3+ hours OR driven less than 1 mile

Why? Driving generates heat, increasing tire pressure by 2-4 PSI. Checking hot tires and adjusting to specification will result in under-inflation when tires cool.

Procedure:

Locate recommended pressure on driver's door jamb placard (NOT sidewall maximum)
- Example: "COLD TIRE PRESSURE: 35 PSI FRONT / 35 PSI REAR"
Remove valve stem cap
Press tire pressure gauge firmly onto valve stem until hissing stops
Read pressure and compare to specification
Adjust as needed:
- Add air if below specification
- Release air if above specification (rare)
Replace valve stem cap (prevents dirt/moisture intrusion)
Repeat for all four tires

Acceptable Range: ±2 PSI from specification is acceptable (e.g., 33-37 PSI if spec is 35 PSI)

Common Tire Pressure Specifications

Vehicle Type	Typical Range
Passenger cars	30-35 PSI
SUVs/Crossovers	32-36 PSI
Light trucks	35-40 PSI (varies by load)
Performance vehicles	32-36 PSI (may vary front/rear)
Temporary spare (donut)	60 PSI

DO NOT use sidewall maximum pressure (e.g., "MAX PRESS 51 PSI") — this is tire maximum capacity, not vehicle recommendation.

State and Federal Tire Regulations

Federal Standards (Commercial Vehicles)

49 CFR 393.75 — Tire Standards:

Steer axle tires: ≥4/32" tread depth minimum
All other tires: ≥2/32" tread depth minimum
Exposed cords or fabric: Out of service (vehicle cannot be operated)
Bulges indicating cord separation: Out of service

State Inspection Requirements

Virginia (19VAC30-70-500):

Tread depth <2/32" in two adjacent grooves = Rejection
Fabric or steel cord visible = Rejection
Knots or bulges in sidewalls = Rejection
Bumps or bulges indicating ply/cord separation = Rejection

Pennsylvania:

Tread depth <2/32" in two adjacent grooves = Rejection
Tread separation = Rejection
Exposed cords or fabric = Rejection

New York:

Tread depth <2/32" measured at most worn point = Rejection
Tire damage exposing cords = Rejection

Texas:

Tread depth <2/32" = Rejection
Tires in unsafe operating condition = Rejection

California & Idaho:

Minimum 1/32" tread depth (less strict than most states)

Key Takeaway: 2/32" is near-universal legal minimum, but professional shops should recommend replacement at 4/32" for safety margin.

When to Replace vs. Repair Tires

Tire Repair Guidelines (Tread Punctures)

Repairable IF:

Puncture in tread area only (not shoulder or sidewall)
Puncture diameter ≤1/4" (6mm)
≥16" separation from previous repair
No sidewall damage from driving on flat

Repair Method:

Patch from inside (removes tire from wheel)
Plug alone is NOT sufficient (temporary only)
Patch-plug combination preferred

Cost: $15-30 per tire

Tire Replacement Required IF:

Tread Depth:

≤4/32" recommended replacement (wet traction degrades)
≤2/32" legal minimum (must replace immediately)

Sidewall Damage:

Any bulge or bubble (any size)
Cuts >4mm depth or any depth exposing cords
Punctures in sidewall (cannot be repaired)

Tire Age:

≥6 years in service (replace per manufacturer recommendation)
≥10 years from manufacture date (replace immediately regardless of appearance)

Structural Damage:

Exposed cords or fabric on tread or sidewall
Tread separation visible (gap between tread and carcass)
Severe dry rot with deep cracks (>3mm)

Puncture Location:

Shoulder or sidewall punctures (cannot be repaired)
Multiple punctures (>2-3 repairs maximum per tire)
Puncture from driving on flat (internal damage)

Common Tire Inspection Mistakes

Mistake #1: Measuring Only Center Tread

Error: Measuring center tread groove only; not measuring inner and outer edges

Example:

Center: 6/32" (looks good)
Inner edge: 2/32" (not measured, at legal minimum)
Result: Missed impending failure; customer returns with tire worn to cords on inner edge

Why Dangerous: Inner edge wear from alignment issues can reach failure point while center still appears adequate

Fix: Always measure inner, center, AND outer tread depths; document all three

Mistake #2: Not Checking Tire Age

Error: Recommending tires are "good" based only on tread depth without checking DOT date code

Example:

Tires measure 7/32" tread depth (50% remaining)
DOT code: 0613 (June 2013 — 12 years old)
Severe dry rot cracking visible on sidewalls
Reported: "Tires good, 7/32" tread"
What's missing: "Tires 12 years old, exceed maximum age, severe dry rot — replace immediately regardless of tread depth"

Consequence: Customer continues driving on aged tires; blowout risk from rubber deterioration

Fix: ALWAYS check DOT date code; age-related replacement overrides tread depth

Mistake #3: Using "Good/Worn" Instead of Measurements

Error: Rating tires as "good" or "worn" without documenting actual measurements

Problems:

No defensible basis for recommendation
Cannot prove tires were at legal minimum if customer disputes
No evidence of condition for liability protection

Example:

Inspection report: "Tires worn"
No measurements documented
Customer: "How worn? They look fine to me."
Shop has no proof to support recommendation

Fix: Document measurements in 32nds for all four tires; include minimum depth for each tire

Mistake #4: Ignoring Uneven Wear Pattern

Error: Reporting tire needs replacement without identifying WHY it wore prematurely

Example:

Front tires at 2/32" inner edge, 6/32" outer edge
Reported: "Front tires worn, need replacement"
What's missing: "Severe inner edge wear indicates alignment issue — recommend 4-wheel alignment after tire replacement to prevent new tires from wearing same way"

Consequence:

New tires installed without alignment correction
New tires wear same pattern (inner edge wear)
Customer returns at 20,000 miles with same problem
Customer blames shop for "bad tires"

Fix: Diagnose wear pattern; recommend alignment when uneven wear present (>2/32" difference inner vs. outer)

Mistake #5: Recommending All Four When Only Two Need Replacement

Scenario 1 (Over-Selling):

Front: 2/32" (worn out)
Rear: 7/32" (60% life remaining)
Error: Recommending all four tires
Correct: Replace front two only; rotate rears to front after suitable mileage

Scenario 2 (Under-Selling on AWD):

Front: 2/32" (worn out)
Rear: 6/32"
Vehicle: AWD/4WD
Error: Replacing only front two
Correct: AWD vehicles require all four tires within 2/32" of each other (diameter matching) to prevent drivetrain damage — recommend all four

Fix: Know vehicle drivetrain type:

FWD/RWD: Can replace two tires if others adequate
AWD/4WD: Require all four tires matched (or shaving service to match new to old depth)

Mistake #6: Not Checking Tire Pressure

Error: Tire inspection without pressure check

Why It Matters:

Low pressure causes edge wear (identifies chronic under-inflation)
Correct pressure prevents premature wear
TPMS light on = customer already aware of issue; not checking creates distrust

Example:

Customer: "My tire pressure light is on."
Tech performs inspection, doesn't check pressure
Customer: "Did you even look at my car?"

Fix: Check all four tire pressures; document in inspection report; adjust to specification

Mistake #7: Missing Bulges on Inner Sidewall

Error: Inspecting only outer sidewall; not checking inner sidewall

Why It's Missed:

Inner sidewall not visible without turning steering wheel or lifting vehicle
Bulges from pothole impacts often occur on inner sidewall (hits road debris, pothole edge)

Consequence: Customer drives on tire with bulge; catastrophic failure (blowout) at highway speed

Fix: Turn steering wheel full lock to expose inner sidewall; use mirror or flashlight to inspect thoroughly

Conclusion

Standards-based tire inspection protects customer safety, ensures legal compliance, and provides defensible service recommendations. By measuring tread depth accurately, diagnosing wear patterns, verifying tire age, and documenting findings systematically, technicians identify legitimate service needs while protecting shop reputation.

Key Takeaways

Measure all four tires — inner, center, outer at multiple points around circumference
Document measurements in 32nds of an inch for defensible recommendations
Check tire age via DOT date code — age overrides tread depth (replace at 6 years or 10 years max)
Diagnose wear patterns — uneven wear indicates alignment/suspension issues requiring additional service
Replace at 4/32", not 2/32" — legal minimum is failure point, not service point
Any sidewall bulge = immediate replacement — do not drive; tow if necessary
Check tire pressure when cold — document and adjust to door placard specification
Sidewall damage cannot be repaired — only tread punctures ≤1/4" are repairable

Want to ensure your shop's tire inspections meet these standards every time? Systematic quality audits catch measurement errors, missing documentation, and inconsistent recommendations. Learn how IQ Auto helps shops maintain professional inspection quality across every vehicle, every technician.

Tire Inspection and Tread Depth Guidelines: Complete Technical Guide

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