GM Issues Service Bulletins for Improperly Cast C8 Corvette Wheels

Affecting 2020, 2021 C8 Corvette models, bulletins cover stock, spare sets of wheels with exposed porosity than allowed in casting process.

No one loves or even likes to know their Corvette is affected by a service bulletin. We want to believe our ‘Vette is perfectly built, and that no harm from the factory or time will come to it. Alas, an issue or two can come up, especially in the first year or so of a new ‘Vette.

Such is the case with the new C8 Corvette. GM issued a pair of service bulletins on March 29 regarding the stock and and spare set of wheels. The bulletins state some 10% of wheels left the factory with exposed porosity greater than allowed from the casting process. It’s even effected at least one of our own forum members.

As shown above, the bulletins make clear that no wheel should look like it was shot with buck shot. The cause of such porosity is trapped air bubbles within the then-liquid alloy metal when poured into the molds. While such defects ruin the aesthetics off the bat, they could also present potential structural issues later on; just ask any C7 Grand Sport owner about their cracked aluminum wheels.

“I just now went out to the garage and thought, ‘I wonder about this whole wheel porosity bulletin,” wrote Phil1098. “‘I’ll just pull the drivers side rear and look’ […] This one sure looks like it qualifies to me. These are the bright silver trident style wheels.”

In another thread, BIG Dave was given a spreadsheet of affected Corvettes currently in dealer inventory, of which there were only 58 thus far. He also looked up the affected part numbers to find out which wheels were under the bulletin. Here they are:

84785086 – Five-open spoke, bright silver, front.

84785088 – Five-open spoke, bright silver, rear.

84785088 – Five-open spoke, carbon flash, front.

84785087 – Five-open spoke, carbon flash, rear.

84600213 – Five-trident spoke, after midnight, front.

84723820 – Five-trident spoke, after midnight, rear.

84600212 – Five-trident spoke, sterling silver, front.

84723819 – Five-trident spoke, sterling silver, rear.

23417380 – 19″ Wheels, Front, Black Aluminum

84735859 – 20″ Wheels, Rear, Black Aluminum

84787695 – 19″ Wheels, Front, 5-Open Spoke, Pewter

84787697 – 20″ Wheels, Rear, 5-Open Spoke, Pewter

The overall bulletins affect 10% of all 2020 and 2021 Corvette models built, amounting to just over 1,300. Affected owners are to head to their local Chevy dealership to have their wheels replaced. The wheels will then receive a final 13mm hole drilled into the rim barrel before recycling, per the bulletins.

Photos: Corvette Forum/Phil1098