ST on a tire: ST (special trailer)
For trailer axles only. Not for a vehicle that steers or drives.
What it changes
Trailer axles neither steer nor transmit drive torque, and ST tires are built for that narrower job: high sustained load at lower speed. They carry more load than a passenger tire of similar size and are not appropriate on a car or truck.
Where it sits: Immediately before the section width.
Sizes in this reference with an ST prefix
Questions
- What does ST mean on a tire?
- For trailer axles only. Not for a vehicle that steers or drives. Trailer axles neither steer nor transmit drive torque, and ST tires are built for that narrower job: high sustained load at lower speed. They carry more load than a passenger tire of similar size and are not appropriate on a car or truck.
- Where does the ST appear on the sidewall?
- Immediately before the section width.
- Does a ST tire take the 1.10 light truck derating?
- No. The 1.10 factor applies to P-metric and Euro-metric tires fitted to a light truck. It is not the rating scheme this type is rated under.
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
- Load Index & Weight Ratings - rimlist, undated reference article (read 2026-08-27)LT against P-metric fitment, ST trailer tires, SL, XL and HL reference pressures
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.