Short Answer
Complete Explanation
The marking “115t” found on many passenger‑car and light‑truck tires follows the standardized system for tire identification. It conveys two key pieces of information about the tire’s dimensions and performance limits.
- Section width (115):
The number 115 represents the nominal section width of the tire in millimetres, measured from sidewall to sidewall when the tire is mounted on its recommended rim width. - Speed rating (T):
The letter “T” is a speed‑rating code defined by the International Organization for Standardization (ISO) and the Tire and Rim Association (TRA). A T‑rated tire is approved for a maximum sustained speed of 118 km/h (73 mph). - Placement in the size code:
In a full size designation, such as 115/70R15 86T, the “115” appears before the slash, while the “T” appears after the load index. When printed without the surrounding numbers, manufacturers may show the combined “115t” for brevity. - Relation to load index:
The load‑index, which indicates the maximum load the tire can carry, is a separate numeric value (e.g., 86) and is not represented by the “t” letter. - Applicability:
The 115 mm width and T speed rating are common on midsize passenger vehicles, especially for tires intended for moderate‑speed, everyday driving.
Common Misconceptions
The “t” in 115t stands for a tire type such as “tubeless”.
The letter is a speed‑rating code, not an indicator of construction type.
115t means the tire can only carry 115 kg.
The “115” denotes the overall diameter of the tire.
FAQ
Is a T‑rated tire suitable for highway driving?
A T‑rated tire is approved for speeds up to 118 km/h (73 mph). While it can be used on highways, it is not intended for sustained high‑speed travel above that limit.
Can I replace a 115t tire with a 120t tire?
Replacing a 115 mm width tire with a 120 mm width tire may affect vehicle handling, speedometer accuracy, and clearance. It is advisable to consult the vehicle manufacturer or a tire professional before changing the width.
Does the "t" affect the tire’s load‑carrying capacity?
No. The "t" denotes speed rating only. Load‑carrying capacity is determined by the separate load‑index number that appears elsewhere in the tire’s size designation.
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