Spy Photos Point to a Major Suspension Upgrade on GMC’s New Pickup
A 2027 GMC Sierra AT4 prototype is riding on larger off-road tires
A prototype of the next-generation GMC Sierra 1500 AT4 has been spotted during road testing in the U.S., and new spy photos reveal one of the truck’s most notable technical updates: a switch to larger off-road tires.

The test vehicle is fitted with 20-inch wheels, but instead of the current model’s standard 275/60R20 tires, it’s running 275/65R20 rubber. Based on visual cues, the tires appear to be Hankook Dynapro AT2 Xtreme. Thanks to the taller sidewalls, overall tire diameter has increased from roughly 33 inches to about 34 inches.

Until now, GM’s full-size pickups have effectively been limited to 33-inch tires because of suspension design and clearance constraints. Owners who wanted larger tires typically had to turn to aftermarket modifications. The latest images suggest that this limitation may be addressed at the factory on the next-generation model.

A larger tire diameter could give the Sierra AT4 more ground clearance, improved approach and departure angles, and a more aggressive stance. It would also help the truck better match competitors that already offer oversized tires on their off-road-oriented trims.
You may also be interested in the news:
How the Yellow School Bus Became a True American Icon
For most Americans, the yellow school bus is more than transportation—it’s a symbol of childhood.
Nissan Versa Is Done: No New Cars Under $20,000 Left in the U.S.
Nissan quietly pulls the plug on America’s cheapest new car—goodbye, Versa
Americans Decide Fast: Half Choose a Car Within a Week
A new U.S. study finds that commuting is the most common reason Americans use their cars.
Why U.S. School Buses Have Black Stripes on the Sides — And What They’re Really For
At first glance, it’s hard to imagine what could be so interesting about American school buses.
Americans Are Now Learning What It’s Like to Own a DeLorean: The Story of a Brand That Walked Away
Fisker Ocean owners are taking matters into their own hands to save their EVs from “digital death.”