How to choose tires for a tractor trailer

A trailer tire does a different job from a tractor tire: it does not pull, it carries load. So the key question is “how many tonnes, at what speed?”. A wrong choice risks blowouts and makes the trailer unsafe on the road.

Start with the load

The total is trailer body weight + payload, shared between the tires. On a single-axle (2-tire) trailer part of the load rests on the tractor hitch; on a 4-tire trailer it is spread over four tires. The combined capacity of the tires should comfortably exceed the loaded trailer weight. Dense loads like grain and especially sand or soil are the hardest on tires.

Ply rating and load index

The same trailer size may come in 10, 12 or 14 PR. Higher ply means more load and more pressure. Using a low-ply tire under a heavy load leads to early sidewall failure.

Speed matters

Capacity depends on speed. Manufacturers usually give more load at low speed (e.g. 10 km/h) and less at road speed (e.g. 40 km/h). For fast road trips use the road-speed value.

Check it on the site

In the home-page visualizer pick your tractor, then “Attach at rear → Trailer”. Choose the tire size, 2 or 4 tires and the load type. The site shows the approximate maximum the trailer can carry for each ply rating and suggests a stronger option if the load is too heavy.

Tips

• Tires on one axle should match in size and ply.
• Set pressure from the manufacturer's table.
• Unload a trailer that will stand for a long time.
• Pulling power is not a tire property; check the tractor's own specifications.

Calculated values are approximate. Never exceed the trailer's registered maximum weight.