There are few factory parts that command the respect given to General Motors’ (GM) Truck Rally Wheel, a staple in the classic truck scene. While many enthusiasts retrofit them to earlier C10s, their true origin lies in the later square body generation. Even for such a well-known wheel, hidden variations exist, as the C10 Truck Nerd recently demonstrated by solving a long-standing mystery.

Typically, Truck Rally Wheels came in two main configurations for the 1973-1987 square body era. The first was a six-lug version fitted to 4×4 models that featured 10 slots and raised lug nut pads. The second was a five-lug version, created for two-wheel drive trucks, that featured 16 slots and flat lug surfaces.

The mystery began when a subscriber contacted Chad about a five-lug wheel that broke the mold, sporting the raised lug pads characteristic of a six-lug wheel. Intrigued, Chad investigated and admitted, “It was a wheel that I hadn’t seen before… at least I thought so.”

Initially baffled, “I had no clue why they were different and what they came on,” Chad said. The answer remained elusive until a separate inquiry about wheel codes led him to re-examine the stampings, noticing the crucial date codes. “Then it hit me. I had figured it out,” he recalled. The unusual five-lug wheels in his possession bore dates from 1988 and 1991.

This discovery pinpointed their origin. These wheels were actually factory equipment for two-wheel drive versions of the square body Suburban and Blazer/Jimmy models that GM continued to produce until 1991. That tidbit is significant because the General’s pickup lines had transitioned to the new Old Body Style (OBS) platform three model years earlier in 1988.

While the mystery has been solved, the reason behind the specific design change remains unclear. Still, Chad declared, “The C10 truck nerd has solved another mystery” and advised fellow enthusiasts hunting for Rallies to double-check their finds to “Make sure you’ve got a matching set.”

Solving the mystery of this oddball Truck Rally Wheel does more than satisfy curiosity. C10 Truck Nerd provided concrete identification for a confusing part variation, helping collectors and enthusiasts identify the correct application for their builds. Here’s to the nerds!