Why the Wheels on the 2022 Cadillac CT4-V and CT5-V Blackwing Only Come in One Size
It all comes down to the tires.
There's no doubt 2022 Cadillac CT4-V and CT5-V Blackwings will take the sports sedan market by storm. How could they not? They're rear-drive sedans that offer manual transmissions. But one detail about them might strike the enthusiast market as odd: There is only one wheel size available from the factory. This means you cannot size the wheels on your Blackwing up or down. Why? It all comes down to the tires.
I'm sure you, like me, spend time messing with online car configurations. And there's almost always an option to size up or down the wheels. Whether or not this affects overall performance is debatable, but at the very least, I know people do it because bigger wheels generally look cool. With its Blackwing cars, however, Cadillac won't even give its customers the choice.
As a quick reminder, the CT4-V Blackwing runs 255/35ZR18s on the front and 275/35ZR18s on the rear. The CT5-V Blackwing runs P275/35ZR19s on the front and P305/30ZR19s on the rear. Both are a set of Michelin Pilot Sport 4S tires developed exclusively for the Blackwing cars. I spoke with Mirza Grebovic, Cadillac's performance variant manager to find out why only 18- and 19-inch forged aluminum wheels are offered from the factory, respectively.
"Because this is the highest level of track performance on these vehicles, we stick as much tire as we can on this platform," Grebovic explained. "Obviously, when you hit the track—flying over the curves at high loads—the tire, wheel, and suspension move a lot. Especially with steering. So we packaged the widest and largest tire we could within the envelope we created so it doesn't contact any other components."
He went on, "The suspension is not mounted hard to the vehicle. It has elastomer bushings so we sometimes put cameras inside the wheel wells to see where the wheels and tires are moving. That helps us develop these envelopes. In some cases, we even put clay on the body and hit the track to see if they're rubbing or touching anywhere. When you see how this thing moves when you are 100 percent on the throttle, you'll understand how much room is needed. So, to package a larger wheel would involve a significant tear-up of the body, the suspension—or even sacrificing the tire performance."
While it's easy to fawn over big engines, big horsepower, and big brakes, all of that is for naught if the car's four contact patches with the pavement suck. The Blackwings' fancy magnetic ride suspension would be useless if there was no grip. So it was very, very important for Grebovic and his team to make sure the tires were absolutely optimized in order to extract every last ounce of performance possible. And then they took away the customer's ability to mess it all up.
"If we went a larger wheel, like a 20-inch on this one"—Grebovic referred to the CT5-V Blackwing parked in front of us—"you would have to reduce the sidewall off that tire. You would then lose all that compliance on the track and it wouldn't give the tire the properties that we're looking for to make it as refined."
Even looking at the cars, it doesn't seem plausible to be able to shove a bigger wheel in the wheel wells. Everything is contingent on those specific tire and wheel sizes; changing it would be like unceremoniously yanking a card out of the card castle.
Grebovic drew special attention to the 305-section rears on the CT5-V Blackwing. If you look closely, the tire has a slightly raised rim protector—about as wide as something you could rest the tip of your fingernail on—that's designed to protect the rim in case the driver hits a curb. Just to have those tires fit correctly on the car, "We actually had to get rid of this on the inside to package the tires," he said. "There is no room in there. So when I say we shoved as much tire as we could in there, I mean we took [the rim protector] off just to gain another two or three millimeters. This was to make sure we could get the performance we wanted out of the suspension and the chassis."
So, no, you cannot option larger wheels onto your Blackwing straight from Cadillac. The performance is too perfectly honed to the existing tires and wheels. This isn't to say you cannot find yourself a nice set of aftermarket wheels and slap them on yourself, however. That would be your right as an American.
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