Ply rating vs star rating on OTR tires is two marking languages, not one toughness score. Ply rating (PR) is the older load-capacity index used mainly on bias OTR. It is not a count of today’s actual plies. Star rating (*, , *) is the radial OTR load mark you copy next to sizes such as 23.5R25. Do not convert them in your head on the PO. Tyre products sit under ISO ICS 83.160.99 (2026). For pit fleets, keep NIOSH mining pages (2026) in the safety file. UNECE vehicle-regulation pages (2026) are the type-approval door if a destination market asks. China Baowu New Materials Co., Ltd. quotes mixed OTR tire sizes when size, mark, quantity, and destination port are written clearly.
Sales talk will say “higher ply, stronger tire.” That sentence hides the radial star system and oversells PR as a ply count. Your machine plate and the molded mark are the spec. A 24PR bias 23.5-25 is not a secret three-star radial, and a one-star radial is not a “light 16PR.” If you need a conversion, you are doing a fleet change with load and inflation tables in hand, not a nickname swap.
Photograph the mark beside the size. If it is stars, write stars. If it is PR, write PR.
Key takeaways
- PR is a bias load index, not a literal ply count.
- Stars are the radial OTR load language; copy *, , or *.
- Never treat PR and stars as interchangeable on one PO line.
- Match the machine plate and inflation practice, not a catalog adjective.
- Mixed containers need the mark on every size line.
What ply rating vs star rating on OTR tires actually measures
Ply rating started when cotton plies were counted. Modern bias OTR still uses PR as a capacity index. More PR usually means a higher allowed load at a stated inflation in that size family. It does not mean you can count layers through the sidewall and get 24.
Star rating on radial OTR is a separate index. One, two, or three stars sit in a different table than PR. The tables live with the tire maker and the association manuals your engineer uses. Your job on a wholesale PO is to copy the mark the machine was plated for.
ISO ICS 83.160.99 (2026) tells you these are off-the-road tyre products. It does not print a homemade PR-to-star chart. Do not invent one on the invoice.
Bias ply rating versus radial star marks
Hyphen sizes such as 23.5-25 usually carry PR. R sizes such as 23.5R25 usually carry stars. That pairing is a habit, not a law. If a sidewall breaks the habit, believe the sidewall.
Load and inflation still belong together. A higher mark without the inflation and the wheel is just ink. Overloaded OTR fails as heat and bead issues, which NIOSH mining safety context (2026) treats as maintenance and operation risk, not as a branding issue.
If you are filling wheel loader tire and mining tire lines in one container, keep PR lots and star lots labeled. The rim diameter can match while the mark family does not.
Matching the machine plate, not the sales nickname
The plate may show a size plus a mark, or a size plus an inflation. If it shows 23.5R25 ** and you order 23.5-25 24PR because someone said it is “equal,” you own the mismatch. Equal is a table exercise with diameters, loads, and clearances. It is not a chat shortcut.
UNECE vehicle regulations (2026) may matter for on-road-related approvals. Most pit OTR never sees that desk. Do not paste UNECE language onto a quarry loader line to look official.
China Baowu New Materials Co., Ltd. can pull mixed sizes. It cannot repair a PO that says “strongest 23.5.”
Need a check before packing? Use quality control as the floor habit: size and mark, pattern, appearance, then pack.
| Factor | Ply rating (PR) | Star rating (*, , *) | Best for | Watch-out |
|---|---|---|---|---|
| Typical construction | Bias OTR | Radial OTR | Copy the mark on the tire you run | PR written on a radial line |
| What it is | Load-capacity index | Radial load mark | Plate-matched wholesale | Thinking PR is a ply count |
| Size example | 23.5-25 plus PR | 23.5R25 plus stars | Separate PO lines | “23.5-25 **” as a hybrid fantasy |
| Conversion | Needs tables and a written change | Needs tables and a written change | Fleet programs with engineering | Chat-based “equivalent” |
| Packing | PR visible on lot mark | Stars visible on lot mark | Mixed containers | Nickname-only packing lists |
Bottom line: Ply rating vs star rating on OTR tires is bias index versus radial stars. Copy one language per line. If you convert a fleet, write it as a conversion, not as a synonym.
How to write ply rating vs star rating on OTR tires on a PO
Format: size, construction mark (hyphen or R), load mark (PR or stars), TT/TL, pattern, quantity. Example shape: 23.5-25, bias, 24PR, TT, E3, 40 pcs. Or: 23.5R25, radial, **, TL, L3, 20 pcs. Use the real marks from your photos, not these as invented defaults.
Do not mix “24PR **” on one line. That string is how destination inspectors stop trusting the list.
Send application, quantity, and destination port with the board. WhatsApp +86 131 7335 1630 if the sidewall photo is unclear.
Load, inflation, and what you should not guess
Without the inflation that belongs to the mark, you do not have a working spec. Do not guess psi from memory on a wholesale chat. Ask the plate, the current sidewall, or the buyer’s maintenance sheet.
Do not invent ISO standard numbers to stand in for PR or stars. Point at ICS 83.160.99 if someone wants the standards map, then return to the molded mark.
Inspect before packing so a one-star radial does not fill a three-star line. That is a size-family error even when 23.5 and 25 match.
Questions buyers still ask
Is a higher ply rating always a stronger radial?
No. Radials are not specced that way. Use stars on radial OTR. PR on a radial PO is a red flag.
Can I replace ** with a high PR bias in the same size?
Only as a planned conversion with load, diameter, and rim checks. It is not a packing-list synonym.
What if the sidewall shows both a number and stars?
Photograph it and send the photo. Do not transcribe from memory. The molded marks win.
Do stars change the rim diameter?
No. 25 is still the rim. Stars change the load mark family, not the 25 in 23.5R25.
What does the factory need to quote?
Size, PR or stars as molded, TT/TL, application, quantity, destination port. WhatsApp +86 131 7335 1630.
Treat ply rating vs star rating on OTR tires as two languages. Copy the plate and the sidewall, then send that board to Baowu Tires or WhatsApp +86 131 7335 1630. Open the OTR program after PR versus stars is settled so the container matches the machine, not a toughness nickname.