A nominal size does not tell you how much work the tyre is approved to do
Commercial listings may show markings such as 146/143L, a load range letter or a ply rating. Passenger and motorcycle products also use load indices and speed symbols. The meanings are standardised, but the safe decision still uses current manufacturer data, inflation information, vehicle limits and local rules.
This guide explains how to read the fields without turning them into fitment advice for an unseen vehicle.
Reviewed 2026-08-26 · For wholesale planning; final specifications and import requirements must be confirmed for each order.
Load index and single/dual markings
A load index is a numerical code linked to a load value under defined conditions. Commercial tyres may show two indices separated by a slash, commonly reflecting single and dual fitment references. Do not treat the second number as a second speed rating.
Confirm the value in the applicable current standard or manufacturer data. Capacity depends on correct inflation and service conditions, and the tyre cannot override vehicle, axle, rim or legal limits. Dual assemblies also require appropriate matching and spacing.
Speed symbols are not target operating speeds
The speed symbol is a letter associated with a standardised speed category under specified conditions. It is not advice to operate the vehicle at that speed, and it does not remove vehicle, load, road or legal restrictions.
When the commercial marking combines two load indices and a letter—such as a format like 146/143L—read the exact manufacturer's data. Do not guess which figure applies to the planned configuration.
Load range and ply rating
Load range letters and ply ratings are additional strength or load-class references used in tyre descriptions. “16PR” does not necessarily mean sixteen literal body plies in a modern radial. Different markets and product families may present information differently.
For procurement, record all markings shown on the approved data sheet. Do not replace one field with another because two products appear similar. The rim, pressure and service tables remain important.
Use markings as order and inspection controls
Put the required size, load index or range, speed symbol, ply reference and application on the RFQ. Require the quotation and proforma invoice to identify the exact product. Before loading, compare visible sidewall markings and technical evidence against the approved line.
At receiving, quarantine mismatches before distribution. Keep photographs and product documents with the order file. If a higher or different rating is proposed, obtain technical approval instead of assuming that “higher” is automatically suitable.
NHTSA materials recognise ISO load indices and ETRTO speed ratings as distinct markings; see the agency's official interpretation for background. Your destination and product may follow additional requirements.
Frequently asked questions
What does a marking such as 146/143L mean?
It commonly combines single and dual load indices with a speed symbol, but use the exact manufacturer's table and applicable standards for the product.
Can I replace a tyre with a higher load index?
Do not decide from one higher number alone. Confirm size, rim, pressure, speed, vehicle compatibility, application and regulatory requirements with qualified data.
Is ply rating the same as load index?
No. They are different references. Record and verify each field provided for the product.
Send a quote request that can be priced properly
Include your tyre sizes, quantities, preferred brands or quality tier, destination port and target timing. Thai Tire can then confirm current availability, a practical size mix and the next export step.
