A tire size with no prefix: Euro-metric (no prefix)
No letter at all. The tire is rated against the European tyre and rim organisation tables.
What it changes
No prefix is a reading, not a missing one. An unprefixed size such as 225/65R17 is Euro-metric, rated against the European tyre and rim organisation's load and inflation tables; P225/65R17 is P-metric, rated against the North American Tire and Rim Association's. The two are the same nominal shape and are commonly cross-fitted, but their rated load at a given pressure is set by different tables and can differ. Treating a missing P as a typographical detail is the mistake this page exists to stop.
Where it sits: Nothing precedes the section width.
The 1.10 factor
A P-metric or Euro-metric tire fitted to a light truck, SUV, pickup, van or minivan has its rated load divided by 1.10. A tire rated 3086 lb is worth 2805 lb in that service. Both manufacturer bulletins cited attribute the factor to federal motor vehicle safety standards, and both apply it to Euro-metric as well as P-metric. An LT tire takes no such reduction.
Divide the rated load by 1.1. A tire rated 3086 lb is worth 2805 lb in that service.
Sizes in this reference with no prefix
Questions
- What does it mean when a tire size has no letter in front of it?
- No letter at all. The tire is rated against the European tyre and rim organisation tables. No prefix is a reading, not a missing one. An unprefixed size such as 225/65R17 is Euro-metric, rated against the European tyre and rim organisation's load and inflation tables; P225/65R17 is P-metric, rated against the North American Tire and Rim Association's. The two are the same nominal shape and are commonly cross-fitted, but their rated load at a given pressure is set by different tables and can differ. Treating a missing P as a typographical detail is the mistake this page exists to stop.
- Where would the prefix be if there was one?
- Nothing precedes the section width.
- Does a Euro-metric tire carry less on a truck?
- A P-metric or Euro-metric tire fitted to a light truck, SUV, pickup, van or minivan has its rated load divided by 1.10. A tire rated 3086 lb is worth 2805 lb in that service. Both manufacturer bulletins cited attribute the factor to federal motor vehicle safety standards, and both apply it to Euro-metric as well as P-metric. An LT tire takes no such reduction.
Where these figures come from
Published values here were read from 2 independent sources:
- Tire code - Wikipedia, revision read 27 August 2026 (read 2026-08-27)Service type letters, construction letters, load range letters and ply ratings, sidewall marking glossary
- Application of Load Inflation Tables, version 20170203 - Nitto Tire (Toyo Tire group) technical bulletin, version 20170203 (read 2026-08-27)P-metric against ISO/Euro-metric load tables, the light truck derating factor, dual fitment reduction, standard load against reinforced
These are independent publishers, not independent measurements. Each one reproduces a table originally set by a standards body, so agreement between them shows a value was transcribed correctly, not that the underlying table is right. Where a figure is safety relevant, check it against the tire manufacturer's own data before relying on it.
Whether Euro-metric tires take the 1.10 light truck derating: yes - the bulletin's heading and text both read 'P-metric or metric tire' (ST-NITTO) against yes - 'When P-metric or metric tire are installed on light trucks' (ST-NEXEN). Retail and forum sources are split, with several stating that the derating applies to P-metric only. Both tire manufacturer technical bulletins consulted state it applies to metric (Euro-metric, also called hard metric) as well, and both attribute the rule to federal motor vehicle safety standards. This site follows the two manufacturer bulletins and flags the split, because the conservative reading is also the one the primary-facing documents give.