The paper describes a careful experimental study of the suspension of tyre-wear particles from a glass substrate. The experiments were carried out in a small wind tunnel and the results used to investigate critical flow conditions for suspension as a function of particle size and shape. The paper is clearly written, though reading it is spoilt by the excessive use of abbreviations and acronyms, even the humble car gets reduced to PC. Most of this can be avoided by using plain language, pronouns, etc. I must admit that I found this annoying and distracting.

The work was carried out in a small wind tunnel, working section 170x54x27 (it might be 27x54) cm, at free stream speeds from 1 to 9.5 ms^-1. The floor of the wind tunnel was covered with roughness elements, except for the glass slide on which the particles to be studied were deposited. Tyre-wear particles come in a variety of shapes and sizes and are, generally, non-spherical, and a key question is whether suspension from a smooth, glass surface provides any guidance for suspension from, say, road surfaces, where surface irregularities will play an important role – as will the action of vehicles moving over the road. Might not the latter be the dominant factor? If that is true, then what is the practical value of this work? These matters deserve some discussion, so that the results can be placed in context.

The boundary layer in the wind tunnel was probably quite shallow, perhaps about 20 cm – it would be helpful to provide the values in the paper along with shear stress profiles. There is no discussion of the mismatch in flow scales (compared with full scale) and its likely consequences, nor of particle inertia and Reynolds number effects. The friction velocity and the probability distribution of the wall shear stress are probably similar to those at full scale, but the associated time and length scales are not and that could be important. Saltation is not discussed – it probably plays no role in the experiments, but I don’t know. What might occur if the glass substrate were longer? Some discussion of these issues is essential.

A question: The term ‘detachment’ is used. I would use suspension – is there a reason for using detachment rather than suspension? How do you separate sliding from detachment?

Other comments on a page-by-page basis follow.

Line 56. What is meant by ‘collision’?

Lines 73-75. Perhaps: “However, for particles with non-spherical geometries, such as those from tyre wear, it is important to evaluate theoretical models of the critical friction by using experimental results for different particle sizes and shapes.”

Line 81. “... the deposited particles often settle in clusters ...”

Line 101. “... water, and were able to ...”

Line 112. Please make clear what is meant by: ‘instance segmentation’?

Line 116. Why is bold used here?

Line 132. Suggested wording: “Conventional image processing techniques have been widely adapted to detect particle images and analyse detachment under turbulent flow conditions in the wind tunnel.” Do you mean in general, or in your laboratory?

Section 2.1. The wind tunnel features a 54 cm × 27 cm cross-section and is 730 cm long. This is confusing as the cross-section dimensions are for the working section, which we learn later to be 170 cm long. It would be useful to add here the dimensions of the substrate and its location in the working section. At present, I have to wait for line 395 to learn: “The detachment experiments were conducted on standard laboratory glass slides (Thermo Fisher Scientific), measuring 75 mm × 25 mm.”

The wind tunnel flow exhausts to the atmosphere. How is the make-up flow provided that ultimately provides the inflow to the tunnel?

Use of a three-wire hot-wire probe requires a yaw and pitch calibration, either assumed or obtained from local  calibrations. Assuming a wire responds to the flow component normal to it is generally considered inadequate. This is not discussed.

Line 156 “... second interval, lit by ...”

Figure 3. “Scanning electron microscopy image of passenger car tire wear particles.”

Line 213. “In particular, it adopts a CSP-style that replaces the C3 block with the C2f module and uses a spatial pyramid pooling fast (SPPF) block for efficient multi-scale feature aggregation.” Am I supposed to understand this sentence? There are other, similar examples.

Line 230. “Manual creation of polygons around microparticles often exceeds 50 particles mm⁻² and is both time-consuming and sometimes inaccurate.” Do you mean that the process of manual creation of polygons around microparticles is both time-consuming and sometimes inaccurate because the density of particles often exceeds 50 mm^-2?

Line 243 “Finally, the fine-tuned model was for a new set of data collected individually from the three seeding approaches.” I don’t understand this sentence.

Table 2. Some entries should have units. Have all the entries been defined? Are they all necessary?

Line 274. One example of the unnecessary use of an abbreviation: “The DSC is defined as:” – “It is defined as:” There are many others that could be resolved in a similar manner.

Line 277. “By computing the DSC for each individual TWP, we were able to obtain a detailed evaluation of the model’s ability to accurately delineate particle boundaries, quantifying the degree at which individual particles of different size and shape detach, and very efficient and sensitive to resolve TWPs capture on different surfaces.” Please rewrite and clarify the final clause, beginning 'and very’.

Equs. 5 and 6. These are properties of 2-dimensional shapes. ‘A’ is the plan surface area of the particle.  Similarly, (6) applies to the surface area in plan. It is not a measure that demonstrates a spherical shape (lines 302, 305).

Line 306. Suggested wording: “This made the metric instrumental in determining how elongated or irregular the particles are, and how they exhibit different detachment behaviour due to variations in contact area and adhesion forces.”

Fig. 5. The lines joining the points have no meaning.

Fig 6. Dice or dice?

Fig. 7. Which is which, density or relative frequency?

Line 354. I don’t see the need of the references: Hancock, line 354; Foken et al., line 361; Zhou et al., 375; Fernholtz etc., lines 375-376. The first is about simulation of stable boundary layers, the second the well-established the log-law, the third and fourth effectively the same.

Equ. 7. How was ‘d’ determined?

Line 378. Measured at what height?

Line 385. How was u* adjusted? 2% uncertainty is remarkably low for hot-wire measurements.

Fig. 8. Suggested caption: “Figure 8. Calibration of u∗ from the profile measurement and the eddy-covariance as a function of the surface wind speed.” Add the value of z. As it stands, the axis has a label of the velocity profile, u(z).

Line 431. Would linear regression be preferable to ordinary least square?

Equ. 9. Define the symbol, N*.

Equ. 10. ‘a’ is an off-set, implying suspension at zero u*. That’s odd.

Line 436. Please define more fully: A (the maximum detachment fraction) and b (the rate of detachment change).

Line 442. C has no units.

Equ. 11. Is ‘d’ the diameter of a sphere?

Fig.9. No side forces are shown, likewise no saltation effects. Can there be direct lift-off? L acts near the leading edge and has along lever arm to the trailing edge, greater than that of the weight. Not obvious that a sphere is more likely to lift off, all else equal.

Section 3.1. Do you need to discuss sliding as well as lifting?

Fig 10b. What do the numbers in the boxes mean?

Lines 483-500. There’s a great deal of the obvious and well known here that could well be moved to introduction.

Line 486. What is meant by ‘acceleration’?

Line 489. How were the speed changes managed?

Fig 11. What is meant by ‘normalised’ in the caption?

Line 523. “For particles larger than 75 µm, gravity term dominates over cohesive forces and the uth∗ increases with size.” Provide a reference, or is this your inference?

Fig. 12. There are no error bars in (a) and (b), just two points in (c). Should the results in (c) be plotted against the mean diameter for each group?

Line 534. “Consequently, the drag force (Fd) and lift force (Fl) can more easily pivot a more spherical particle off the surface,” – not obvious really, see comments above on Fig. 9.

Fig. 13. Note u* scales change. Plot (d) against mean C for each group?

Fig. 14. Tyre-wear results for particles of equivalent diameter around 20 micro-m would be very useful.

Conclusions, Line 586-589. This is true.  Note though that De and C are actually measures of the top or plan view of the particles, not of the whole, three-dimensional shape.

App. A1 is about Yolo. Is it needed? Please add brief explanations within A2, A3 and B1.

Fig. C1. Move to main text. Plot using dimensionless speed, U/Uref and (ln((z-d)/H), where H is the boundary layer depth, for the whole boundary layer and add the associated dimensionless shear stress profiles.

Fig. D1. How was acceleration from one u* to the next managed? What was the time-speed profile?

Overview

This manuscript presents an experimental modelling study investigating the detachment mechanisms of tire wear particles (TWPs). The authors utilized a laboratory test stand to generate pristine passenger car and truck tire particles, to avoid the confounding factors of road wear, environmental aging, and road dust. These particles were dispersed onto a glass substrate using a new method developed in this study. Using an established model, the study successfully identifies the detachment of these particles from a glass substrate within a wind tunnel. By investigating physical parameters such as size and morphology, the authors have established a framework for determining the critical velocities required for particle removal. This work represents a significant step toward characterizing the fundamental mechanisms controlling TWP transport.

While the topic is highly relevant to Aerosol Research and provides valuable insights into detailed detachment parameters, the manuscript is written in dense technical language that may be inaccessible to a broader audience. I recommend the manuscript for publication after addressing the following comments.

Specific Comments:

1. As this study focuses exclusively on pristine lab-generated TWPs, what specific insights should future studies apply when moving into natural environments (real-world, aged tires)? Additionally, could the authors further emphasize the practical benefit of achieving this higher level of detachment accuracy for environmental modeling?
2. Regarding the resolution selection in Section 2.6, did the authors consider more robust methods for determining the optimum resolution beyond the sensitivity analysis in Figure 5? For instance, identifying the "elbow point" where increases in resolution no longer yield significant gains in mAP relative to the increase in inference time.
3. Section 2.7 (Line 348) mentions benchmarking against commercial equipment and refers to Figure B1. However, Figure B1 shows the size distribution of car TWPs without clearly identifying the reference data. Were these distributions measured by commercial equipment? Please elaborate on the specific benchmarking procedure and the equipment used.
4. Several sections use highly specialized computer science terminology that could be simplified for the Aerosol Research audience. For example, the description on Lines 213–214 regarding the model architecture could be made more intuitive, such as:

"The model has been upgraded with a CSP-style with a C2f module that retains more details without getting slower. It also uses spatial pyramid pooling fast (SPPF), a high-speed vision tool that lets it accurately identify objects of different sizes simultaneously."

I suggest that the authors review the manuscript and rewrite or elaborate on technical terms to ensure the work is accessible to aerosol scientists who may not be experts in Deep Learning.

Technical Comments:

1. Acronyms: Please define all acronyms upon their first use in the text. Key examples to address include:

Line 15: PE

Line 96: DL

Line 158: CTA

Line 224: mAP.

1. Line 365: The text says "see appendix." It is unclear if this refers to the appendix of this manuscript or the referenced paper (Thomas et al., 2009). If it is the latter, please include a brief description of the automated software tool in this manuscript’s own appendix for clarity.
2. Line 378-381: In Figure C1 (Lines 378–381), it is unclear which one is the derived friction velocity (u_*) and the eddy covariance measurement (u_*,EC). Please use distinct colors or markers to clarify.
3. Line 454: Specify the exact type and material of the "microspheres" used by Shao and Lu (2000) to provide a better baseline for the TWP comparison.
4. Line 473: Lower case for “unique particle identifiers”.
5. Line 554-555: For the adhesion analysis, provide the specific gamma values and citations for the natural dust and sand particles used as a comparison.