The Tyre Dispatch Workshop Tyre Report
First 1,500 Inspections. Tread depth, wear geometry, defect tags, age and certification marks — documented through a working tyre workshop in Te Puke.
What this report examines
This report presents descriptive findings from a structured workshop dataset of tyres physically inspected and documented by Tyre Dispatch in Te Puke, Bay of Plenty. Each record can combine multi-point tread measurements across the tread face, an operator condition assessment, defect tags, DOT age information, specification data, sidewall certification marks, written notes, photographs and video.
Its purpose is not to estimate the condition of tyres on New Zealand roads. It describes tyres reaching a working tyre business, and provides an evidence base for recurring workshop patterns, consumer inspection advice and future research questions.
Interpretation boundary
These findings describe tyres documented in one workshop. Worn, damaged and replacement-ready tyres are expected to be over-represented compared with a random roadside or fleet sample. Percentages describe this dataset, not the New Zealand vehicle fleet.
The strongest signals in the first milestone
Each finding states its unit and denominator. Findings affected by an unresolved question link to the relevant open gap.
Where the recorded measurements sat
Why this report does not say “illegal”, and why 1.5 mm is a numerical threshold rather than the applicable minimum
Three features of the protocol prevent a compliance claim. First, depth is measured at a single circumferential position, while the requirement applies around the whole circumference. Second, the requirement applies to principal grooves — defined in the VIRM as those containing tread-wear indicators. Other grooves are secondary and may legitimately wear away during service. Where a shallow reading falls in a decorative or secondary groove the operator records that in the entry notes and such a groove is never the basis of a fail on its own; the structured depth columns, however, carry no per-groove principal flag, so that distinction lives in the notes rather than the numeric fields. Third, tyres without moulded indicators are assessed across at least three-quarters of the tread width instead, which is a different test again.
The threshold itself is also not universal. Winter tyres require 4 mm under VIRM reason for rejection 16, not 1.5 mm. There is no structured winter-tyre field, so the uniform description below uses 1.5 mm throughout. Winter and snow tyres that were encountered are flagged in the free-text notes, 13 cohort records carry such a note, and those entries are assessed against the 4 mm winter limit in their notes. See Open Gap 1. The figures below are therefore a uniform numerical threshold applied to a mixed population, reported as “at or below 1.5 mm at the lowest recorded measurement point”. They are a conservative wear indicator, not a compliance rate.
Tread depth grouped by bands around the 1.5 mm threshold
The same records summarised three ways
Lowest recorded point
Mean of recorded points
Highest recorded point
Full distribution at 0.5 mm resolution
Bands below 1.5 mm collapsed into a single bar
Lowest recorded point
Mean of recorded points
Highest recorded point
Wear shape calculated from the recorded measurements
This classification is computed from the recorded groove depths across the tread face. No photograph or operator-selected wear label contributes to it, although the measurements themselves are operator-recorded. The algorithm is published below so the classification can be reproduced or challenged.
Wear geometry classification
Classes assigned in order; the first match wins
Edge worn low versus centre worn low, where the measurements identified a location
Calculated from measurements
(both shoulders, inside or outside)
centre-low
outside edge
The edge most often lowest is the one drivers cannot see
Classification algorithm
Published so the classification can be reproduced. Classes are mutually exclusive because assignment stops at the first matching condition. The two “normal” rows in Figure 3 are a reporting split of one class at the 1.0 mm spread line, not separate algorithm outputs.
What was recorded, and in what unit
How defect counts are counted
Operator condition category
Single-select operator assessment
Workshop screening verdicts
Workshop screening verdicts
Operator verdict recorded at documentation
Defect-tag frequency — distinct records
Unit: distinct tyres
Evidence volume — defect photographs
Unit: photograph files · no denominator by design
Reading Figures 7 and 8 together
Wear and wire exposure by location
Tag location comparison
Distinct records carrying each tag
centre wear
centre wire
Exposed or cut cords are a listed reason for rejection under VIRM 10-1, reason for rejection 13(c). Both tag pairs are subject to Open Gap 2.
Inflation-related wear signals
Original visual evidence
Which studies this can and cannot be compared with
Percentages from tyre-condition studies look comparable and usually are not. What determines comparability is the sampling frame: tyres sampled at replacement, vehicles inspected in service, or specimens tested in a laboratory. The frame for each study referenced here is stated before any comparison is drawn.
| Study | Sampling frame | Unit | Threshold | Role here |
|---|---|---|---|---|
| Tyre Dispatch (this report) | Mixed-purpose workshop records: removals, stock, reference and training entries | Tyre-entry record | 1.5 mm applied uniformly | Primary dataset |
| TyreSafe tread-depth surveys | Tyres at the point of replacement, UK outlets | Tyre | UK 1.6 / 2.0 mm | Closest available comparator, once a removal subset exists |
| NTDA TyreCheck 2025 | Vehicles inspected at participating UK locations | Vehicle | UK 1.6 / 2.0 mm | Context only — different unit |
| NTSB | Crash investigation and regulatory review | Varies | Varies | Structural model for reporting |
| NHTSA / TRL | Laboratory ageing research | Test specimen | Laboratory outcomes | Scientific background only |
Record purpose
Every record carries a purpose. Within the cohort: 1,455 customer removals, 41 new-stock documentation records and 4 on-vehicle checks. The 638 records that predate the purpose field were classified on 27 July 2026 by a fixed rule set by the author: single-photograph entries in the first 300 records are on-vehicle checks, records graded new are new stock, and the remainder are removals. Each record classified this way carries a provenance marker in the database. Because the 45 non-removal records sit in every denominator, headline tread figures sit slightly above a removals-only rate; that recut is registered for the next milestone.
What can be said now
UK point-of-replacement surveys consistently find that a large majority of tyres reaching replacement sit at or near the legal limit, with a substantial minority already below it. The direction of the results in this report is consistent with that pattern, which is what would be expected of any dataset weighted towards tyres being removed.
No numerical comparison is drawn. The legal threshold differs, measurement protocols differ, geography and vehicle mix differ, this is a single workshop rather than a national outlet network, and this dataset is not yet restricted to tyres at the point of replacement. A defensible rate-to-rate comparison requires that subset first.
Why the other studies are background
NTDA TyreCheck inspects vehicles rather than sampling tyres at replacement, so its percentages describe a different unit and a healthier population; it is cited for its classification approach and for reporting national and regional results separately. NTSB work is built on crash investigation and is used purely as a model for report structure. NHTSA and TRL conduct controlled laboratory ageing research, cited as background and, in TRL’s case, as a model for stating plainly what a limited sample cannot support.
A broad sample, concentrated in common specifications
Speed ratings
Top eight shown
Tread pattern direction
Complete coverage of the extract
Pattern classification has held steady as the dataset has grown
DOT manufacture years — most recent 12
Sorted by year, not by count
Country of manufacture
Top 10 shown
Pre-2000 manufacture years are decade-ambiguous
Country coverage reconciles once the “Unknown” values are accounted for
Age is the next milestone’s primary research question
Certification systems documented
Systems overlap; one tyre may carry several
E-mark approval authority
Which UNECE state granted type approval
What an E-number does and does not mean
The number inside the E-mark circle identifies the UNECE member state whose authority granted the tyre’s type approval. It does not indicate where the tyre was manufactured, where it was sold, or that it was individually inspected in that country. Country of manufacture is recorded separately from the moulded country stamp.
UTQG grades recorded
Three separate denominators — see caption
Treadwear (top 12)
Traction
Temperature
UTQG coverage
EU-label coverage
Catalogue separation
A labelled evidence dataset, not a photograph count
The uploader preserves context around each tyre. Its current version captures separate shoulder angles and profiles and left, centre and right tread close-ups, which is what makes the geometry analysis in Section 03 possible.
Checked and absent: recording what was looked for and not found
A blank field is ambiguous, and its meaning shifts with capture era. From roughly entry 350 the protocol has recorded these details at inspection, so a blank generally means the marking was absent or not visible. Before that the field simply did not exist at capture: part of the early range has since been backfilled from sidewall photographs, but a marking can be present on one of those tyres and still be unrecorded. The capture protocol records explicit “checked and not present” outcomes, which converts part of the missing data into a positive finding.
| Field | Confirmed absent | Cohort | Effect on interpretation |
|---|
Records by uploader version
Capture capability expanded over time
Sidewall detail photography coverage
Records carrying each dedicated close-up
| Entry range | Recorded | Missing | Cause |
|---|
Why this matters for external researchers
Most tyre datasets provide either product specifications or controlled laboratory results. This one adds natural workshop variation: wear, damage, age, dust, lighting, mixed brands and classes, and repeated labelled views of the same physical object. That depth suits descriptive research and computer-vision development, provided the limitations in Sections 09 and 10 are respected.
How the dataset and analysis were produced
Data dictionary
Every variable reported in this document, with its unit, denominator and source. A percentage is valid only where numerator and denominator share a unit.
| Variable | Unit | Denominator | Cohort | Notes |
|---|
Cohort derivation and data freeze
| Analysis | Usable | Confirmed absent | Missing / unassessed | Cohort |
|---|
Open methodological limitations
Two limitations remain open: one threshold-applicability question and one defect-assessment denominator. Each is stated in full rather than left implicit, and marked inline where it affects a result.
| Gap | Question | Affects | Can it be closed retrospectively? |
|---|
What this report can and cannot establish
Appropriate use
These data suit describing workshop-documented tyres, generating testable hypotheses, illustrating real defects, improving consumer and trade inspection practice, and supporting computer-vision research. Any claim about the national fleet requires a separate probability-based sampling design.
What can reasonably be concluded from this milestone
Conclusions are restricted to the documented sample and distinguish observed patterns from explanations requiring data this study does not hold.
Recommendations
| Audience | Recommendation | Evidence basis |
|---|
Questions created by this milestone
Reporting structure from 2,000 records onward
| View | Purpose | Example |
|---|---|---|
| Cumulative | Strongest overall evidence as the dataset grows. | Records 1–2,000 |
| New cohort | Prevents a large historical sample from masking recent change. | Records 1,501–2,000 |
| Tyre weight | Per-tyre weight capture was added to the protocol late in this cohort. The next report can relate weight to size, construction and wear. | Records 1,501–2,000 |
| Milestone comparison | Shows whether each headline percentage is stable, rising or falling. This replicates findings without implying a probability sample, which is why no confidence intervals are used. | First 1,500 versus new 500 |
These questions are commitments registered here in advance and will be answered in the next milestone report. They are not links.
Referencing and reusing this report
A stable address, visible version number, declared cohort, published denominators and permanently archived milestones make this series citable. Superseded versions remain available rather than being overwritten, so a figure quoted from an earlier version can still be located and checked.
Suggested citation
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Licence
Report text, tables and figures: Creative Commons Attribution 4.0may be quoted with attribution to this report and its version number.
Aggregate data files: may be quoted with attribution to this report.
Dataset and photographs: the inspection dataset, its measurements, photographs and video are the exclusive property of Taylor Houghton, all rights reserved. They are not covered by any licence on this page. Licensing of the dataset for research or machine-learning use is available by arrangement: email@tyredispatch.co.nz.
Data availability
Public now: the JSON and CSV linked above. Both are generated from the same figure definitions that render this page, so they contain every count, unit, denominator and caveat shown here.
On request: a de-identified record-level extract for named research purposes, and access to selected inspection images, both case by case.
Not released: customer names, contact details, vehicle registration details, commercial pricing and supplier information.
Process: written request to the contact below stating purpose, institution and intended outputs.
| Version | Date | Status | Change |
|---|
Research and media enquiries
Aggregate findings may be cited with attribution to this report and its version number. Please cite the version, since figures may be revised in a later edition.
Author: Taylor Houghton, Director, Tyre Dispatch NZ
Location: Te Puke, Bay of Plenty, New Zealand
External sources used for context and report design
All counts and findings come from the workshop dataset itself. The sources below provide regulatory requirements, comparator studies and models for transparent observational reporting. Their role is stated in Table 1.
- NZ Transport Agency Waka Kotahi. Vehicle Inspection Requirements Manual, In-service certification (WoF and CoF), 10-1 Tyres and wheels. Source of: reason for rejection 15 (1.5 mm around the whole circumference within all principal grooves normally containing moulded tread-depth indicators, or across three-quarters of tread width where none); reason for rejection 16 (4 mm for winter tyres); reason for rejection 13(c) (exposed or cut cords); Note 2 (definition of principal versus secondary grooves); Note 3 (winter-tyre definition and the limits of the 3PMSF marking as evidence).
- TyreSafe. Tread-depth surveys at the point of replacement, produced with partners including National Highways. Closest available comparator by sampling frame.
- National Tyre Distributors Association. (2025). TyreCheck 2025 vehicle inspection survey. Vehicle-unit context, not a point-of-replacement comparator.
- National Transportation Safety Board. (2015). Selected Issues in Passenger Vehicle Tire Safety. NTSB/SIR-15/02. Structural model for findings, conclusions and recommendations.
- Evans, L. R., & MacIsaac, J. D. (2014). NHTSA Tire Aging Test Development Project Phase 2. DOT HS 811 885. Laboratory background on tyre ageing.
- Transport Research Laboratory. (2019). Tyre Ageing: Its Effect on Material Properties and Structural Integrity. PPR904. Cited also as a model for stating plainly what a limited sample cannot support.
- STROBE Initiative. Checklists for transparent reporting of observational studies. This report is STROBE-informed and does not claim formal compliance.
- Zenodo. Research repository and persistent identifier service. Proposed for the final report and aggregate data package.
How this differs from laboratory tyre studies
NHTSA and TRL use controlled programmes to examine material properties and structural durability under known conditions. This report records naturally occurring workshop variation with unknown service histories. It can show what was observed and how often it was documented within one workflow; it cannot reproduce laboratory control or assign a mechanical cause.
