Hub rings, along with the wheels they are coupled with are often subjects of “misleading information.” Although their function is simple and straightforward, there are many myths about them. Their function, the types of materials they are made from, and the story behind their creation have been subjected to a game of telephone which has lasted far too long. As a result, we feel that it is necessary to clear the air on this topic.
A hub ring, in its simplest form, is a reducer bushing. When the wheel/tire is being mounted on the car, the hub ring helps non-hub centric wheels to be truer to the center of the hub by filling in any gaps. A common misconception is that there is constant stress being applied to the hub ring, which is in fact, false. As soon as the lug nuts/bolts are fitted and torqued down, all stresses on the hub ring are removed.
In the 1970s, a company named Western wheel was contracted in to make OEM wheels for GM’s Pontiac Firebird. General Motors asked for the wheels to be hub centric with a tolerance of .400 for the mounting surface, an amount that is nearly impossible to see with the naked eye. Within a few months of the vehicle being available for sale, a handful of Firebirds were coming back to dealerships on flatbed trucks. Customers complained that they had gotten a flat tire and they were unable to remove the wheel off the hub; the culprit was galvanic corrosion.
Galvanic corrosion is a phenomenon that occurs when two dissimilar metals (in this case, an aluminum alloy wheel and a steel wheel hub) come into contact whilst in the presence of an electrolyte. This can cause the location where these two metals meet to rust, making it very difficult to remove wheels if the corrosion is significant enough. In places where road salt is used, galvanic corrosion can happen very quickly with catastrophic results.
In the early 80s, Chrysler partnered with the late Carroll Shelby to develop a limited-edition Dodge Dakota. Chrysler required the wheel hub to be created from a material that would be impervious to galvanic corrosion from aluminum wheels. Ron Pushea, a mechanical engineer and machinist specializing in vehicle componentry became involved in the Dakota project. Ron’s suggestion was to have the center bore of the wheel to be enlarged, with a sleeving to go over the wheel hub, acting as an O-ring to protect it from any corrosion. This polycarbonate sleeve became known as the hub ring.