BYD apologized on Wednesday after a factory mix-up swapped front and rear wheel rims on certain Great Tang electric SUVs — an admission that lands on a model which sold about 14,000 units in October at prices starting from 239,900 yuan (about $35,800).

The defect is not a crash. BYD's own testing found no effect on handling and no safety risk, the company said, and no safety incidents have been reported. What it is instead is a quality-control failure with a measurable cost: BYD will replace the rims at no charge, restart warranty coverage as of Wednesday, and cover owners' transportation.

What went wrong inside the factory?

BYD said in a Weibo statement that its investigation pinned the fault on a supplier, Hubei Boyu Industrial, based in Hubei province. The supplier made a code entry error that led to the wrong installation, according to CnEVPost. In plain terms, the production system drew the wheel-and-tire package for each axle from the wrong part code, so the two axles came out reversed.

BYD said it has corrected the faulty system, and the supplier has begun carrying out extra visual checks along its assembly line, according to Bloomberg.

One number is conspicuously missing. BYD did not say how many vehicles were affected, so the scale of the service campaign stays inside the company's own reporting. It is also the figure that determines how many service bays, loan cars and replacement rims the remedy consumes.

Which rims ended up where?

The factory specification makes the swap visible at a glance. Owners cited by CnEVPost laid out the intended setup:

• Front axle: 8J×20 rims (rim width in inches, then diameter) wrapped in 255/50R20 tires (millimetres, aspect ratio, rim diameter)
• Rear axle: 9J×20 rims wrapped in 275/45R20 tires — the wider pair, on the axle that carries the heavier load

Because the code was transposed, owners reported the wider rear rims sitting on the front axle, while the narrower front pair had ended up on the rear. Wider rubber on a narrow front rim changes how the tire seats and wears; a narrower front rim on the rear leaves that axle with a smaller contact patch than the factory intended.

Some owners said they feared excessive tire wear and safety risks while driving. BYD's own testing found no effect on handling and no safety risk, the company said.

What do owners get?

For the owners holding one of these cars, the remedy is free and immediate:

• Inspection and rim replacement at nearby service centers, at no cost
• Warranty coverage that starts over as of Wednesday
• Loan replacement cars, or reimbursement for getting around while the car is in the shop

The mistake surfaced when a number of owners posted complaints on the internet, according to Bloomberg. The sequence is worth noting: the company moved after the customers did. That is the cost of a quality slip a single data-entry error can create in a high-volume assembly line.

Why it matters for BYD's upmarket push

The Great Tang is the flagship of BYD's Dynasty lineup, and the model plays a key role in the company's move upmarket. October's roughly 14,000 units put it at a scale where supplier discipline becomes BYD's problem, not just the supplier's.

Price sharpens the arithmetic. At 239,900 yuan (about $35,800), the Great Tang sits above the volume segment, where buyers read build detail closely and a free rim swap plus a restarted warranty is a real gesture rather than a rounding error.

A code entry error is not a design failure, and no safety incident has been reported. But the error strikes a nerve for China's auto industry, where regulators are paying increasing attention to quality and durability.

There is a second-order signal here. Extra visual checks along an assembly line are cheap insurance; the reputation cost lands on the brand that owns the badge, not on the supplier that made the slip. BYD has corrected the system and shifted the burden onto its service network. What it has not done is publish a count — and until it does, the size of the bill is a guess.