Tread depth is the distance from the tread surface to the bottom of a main groove at a defined location.
Tread depth is the distance from the tread surface to the bottom of a main groove at a defined location.
One center reading does not describe the whole tire. Professional inspection records inner, center and outer zones and uses additional circumferential points when wear is irregular.
An average can describe overall wear, but it must not hide the minimum representative groove. Report both the lowest value and the cross-tread spread.
Use a traceable measurement method, consistent units and position labels. Clean and calibrate automated equipment and keep a defined manual-verification process.
What the finding means
One center reading does not describe the whole tire. Professional inspection records inner, center and outer zones and uses additional circumferential points when wear is irregular.
An average can describe overall wear, but it must not hide the minimum representative groove. Report both the lowest value and the cross-tread spread.
Possible contributors
A visible pattern or measured condition is evidence, not proof of one component failure. Compare all tire positions and combine the tire findings with pressure, alignment, wheel-end and service-history data.
| Condition to consider | Role | Verification |
|---|---|---|
| Probe placed on a wear bar or raised feature | Possible contributor | Verify with measurements and vehicle history |
| Gauge held at an angle | Possible contributor | Verify with measurements and vehicle history |
| Debris or stones filling a groove | Possible contributor | Verify with measurements and vehicle history |
| Only the deepest groove selected | Possible contributor | Verify with measurements and vehicle history |
| Automated capture affected by path, speed or contamination | Possible contributor | Verify with measurements and vehicle history |
Workshop inspection procedure
- Identify the main usable grooves
- Keep the gauge base square to the tread
- Measure across the full usable width
- Repeat around the circumference when variation exists
- Verify low or unusual automated results manually
Pressure, tire position, measurements, photographs and vehicle condition should be recorded before correction. That evidence makes the recommendation understandable and supports future comparison.
Service decision and follow-up
Use a traceable measurement method, consistent units and position labels. Clean and calibrate automated equipment and keep a defined manual-verification process.
Inspect the opposite tire and the other axle before finalizing the recommendation. When corrective work is performed, set a verification point so the workshop can confirm that new wear is no longer progressing abnormally.
Tread depth does not override a bulge, exposed reinforcement, suspected separation, severe run-flat history or damage outside an approved repair procedure.
Frequently asked questions
Where should tread depth be measured?
Measure the principal grooves at several points around the tire and across the tread, avoiding wear bars and localized debris.
Should the highest or lowest reading be recorded?
Record the minimum representative reading and note meaningful variation across the tire.
Can a drive-over scanner and handheld gauge be used together?
Yes. Automated scanning provides fast multi-tire screening, while a handheld gauge can confirm unexpected or localized readings.
What should be done before measurement?
Remove stones or debris where safe, verify the measuring tool and ensure the tire is accessible and correctly identified by position.
Technical review edition · Published 17 July 2026.