23:28 25-12-2025
GMC Sierra 1500 AT4 prototype tests larger 34-inch off-road tires
Spy shots show the next-gen GMC Sierra 1500 AT4 on 275/65R20 (34-inch) tires, ending the 33-inch cap for more clearance and factory off-road capability.
A next-generation GMC Sierra 1500 AT4 prototype has been spotted in the United States during road testing, and fresh spy shots point to a notable mechanical change: a shift to larger off-road rubber.
The test truck rolls on 20-inch wheels, but instead of the current model’s 275/60R20 tires, it’s wearing 275/65R20s. By the looks of it, the set appears to be Hankook Dynapro AT2 Xtreme. Thanks to the taller sidewall, the overall rolling diameter grows from roughly 33 to about 34 inches.
Until now, full-size GM pickups were effectively capped at 33-inch tires due to suspension packaging and clearance constraints, prompting owners to turn to modifications for bigger setups. Judging by these images, the next generation is set to remove that limitation right from the factory.
Upsizing the diameter could grant the Sierra AT4 more ground clearance, better approach and departure angles, and a tougher stance. It also helps the truck align more closely with rivals that already offer large tires in their off-road trims. On paper the tweak looks simple, yet it addresses a common workaround among owners and speaks to what matters in this segment: capability that’s built in, not bolted on later.