Hercules Strong Guard ST Tires

The Hercules Strong Guard ST is a premium high-speed radial trailer tire (ST-metric), built for owners who tow regularly and demand higher durability than basic ST radials offer. It is rated for trailer service only (ST) and must never be mounted on a tow vehicle.

The internal structure is engineered specifically for the thermal and structural stresses of heavy towing. Every size features high-tensile steel belts reinforced with two full-width nylon cap plies to maintain casing integrity at sustained highway speeds—backed by an N speed rating (up to 87 mph). To combat the primary cause of trailer tire failure, Hercules incorporated COOLCOURSE Technology, a specialized heat-resistant compound designed to dissipate internal operating temperatures. Externally, a heavy-duty curb guard shields the upper sidewall from impacts during tight maneuvers into campsites and docks. On pavement, four wide circumferential grooves paired with a firm, sturdy center rib optimize footprint pressure, resisting hydroplaning and keeping the trailer tracking straight behind the tow vehicle without swaying or wandering.

It is backed by the Hercules Performance Promise, which includes a 6-year limited protection policy, Road Hazard Protection (free replacement during the first 50% of tread life), and a 45-day trial period.

Three operational habits ensure maximum service life, regardless of brand. Inflate to the maximum cold pressure molded on the sidewall before every trip. Select a load range that provides a safety margin over your fully loaded trailer weight. Finally, replace tires based on the DOT date code rather than remaining tread depth, as trailer tires age continuously even when parked.

Best-suited for: Travel trailers, fifth wheels, boat trailers, enclosed cargo trailers, car haulers, and heavy equipment trailers. Popular sizes for the Hercules Strong Guard ST include ST225/75R15, ST205/75R14, ST205/75R15, ST235/80R16 and ST235/85R16.

Tire Best Features:

• N speed rating (certified up to 87 mph) for safe, sustained highway towing.

• High-tensile steel belts with double nylon cap plies deliver maximum casing stability under heavy loads.

• COOLCOURSE Technology actively manages internal friction and reduces heat buildup.

• Heavy-duty sidewall curb guard protects against curb scuffs, impacts, and scrubbing damage.

• Four circumferential grooves with a sturdy center rib ensure exceptional wet tracking and sway control.

• Hercules Performance Promise includes 6-year coverage and Road Hazard protection.