We hear it all the time: What’s the widest tire I can fit under my car? Bigger is always better, right?
Not necessarily. From a performance standpoint, what matters more than tire width is optimal wheel width to support the chosen tire size. But don’t take our word for it. Let’s look at some data from our many years of tire testing.
What made our CRX faster: wider tires or wider wheels?
One of our tire testing mules, the One Lap CRX, can use a staggered wheel fitment: 15×9-inch wheels up front and 15×8-inch wheels in the rear.
But we also have several sets of each of those wheels, so it’s easy to run a variety of front wheel and tire sizes for comparison. And since our front-drive machine achieves most of its grip work with the front wheels, it’s easy to quantify the effects of these different setups merely by swapping out the fronts.
Let’s look at some data from a test we did at Harris Hill Raceway using the BFGoodrich g-Force Rival in two sizes mounted on two different front wheel widths. Both tire sizes have the same overall diameter, so gearing is unchanged. And the wheels share the same ET36 offset, so track width also remains constant.
We can see that going from a 205mm to a 225mm tire on the same-width wheels delivered no better lap times. But mount that 225mm tire on a wider wheel, and suddenly the car has more grip everywhere, circulating a solid half-second quicker.
Still not a believer in properly matched wheels? Here’s some data collected when testing the Maxxis VR-1 200tw street tire, again at Harris Hill.
Before hitting the One Lap of America, first a major investment: the right wheels. Photography Credit: Tom Suddard
We’ve also tested this concept on our more recent One Lap of America ride, a McLaren 720S. As a mid-engine, rear-drive machine, this car comes from the factory with taller, wider rear wheels.
But there’s still room for improvement with wider wheels on both ends. Custom forged wheelmaker Finspeed made us a set that’s 1 inch wider front and rear. Here’s some Harris Hill data comparing Michelin Pilot Sport 4S tires on the OE wheels versus the same tires on the Finspeeds.
Notice a trend? For optimal on-track performance, we have seen faster laps with the wider wheels.
This also usually equates to about half an inch wider than the measured tread width, but it can vary a bit…
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