Drivers constantly inquire: What is the widest tire I can mount on my vehicle? Wider must equate to superior performance, no?

Not always. For peak handling, wheel width optimized for the selected tire size often outweighs tire width alone. Do not just trust our assertion - examine data from extensive tire evaluations.

What accelerated our CRX: broader tires or broader wheels?

Our tire test vehicle, the One Lap CRX, accommodates staggered setups like 15x9-inch front wheels and 15x8-inch rears.

With multiple sets available, comparing various front wheel and tire combinations proves straightforward. As a front-wheel-drive car, it generates primary grip upfront, allowing clear measurement of setup impacts by altering only the fronts.

Consider results from Harris Hill Raceway using BFGoodrich g-Force Rival tires in two sizes on differing front wheel widths. Both tires maintain identical overall diameter for consistent gearing, and wheels share ET36 offset to preserve track width.

Switching from 205mm to 225mm tires on identical wheels yielded no lap time gains. However, pairing the 225mm tire with a wider wheel boosted grip across the lap, shaving a solid half-second.

Doubtful about wheel-tire matching? Review Maxxis VR-1 200tw street tire data from Harris Hill.

Prior to One Lap of America, a key upgrade: appropriate wheels. Photography Credit: Tom Suddard

We applied this principle to our recent One Lap entry, a McLaren 720S. This mid-engine rear-driver arrives with factory-staggered taller, wider rears.

Yet wider wheels front and rear offer further gains. Custom forger Finspeed supplied a set one inch broader overall. Harris Hill data contrasts Michelin Pilot Sport 4S tires on stock wheels against the same on Finspeeds.

A pattern emerges: wider wheels consistently deliver quicker laps for track performance.

Optimal wheel width typically measures about half an inch wider than tread width, though variations arise from tread profiles and absent standards. Lacking half-inch wheel options, the next full inch often suffices.

Hoosier presents an outlier. Its A7 and R7 DOT R-compounds mimic race tires in build and size despite quasi-street legality. Stiff sidewalls demand less wheel support than standard street rubber, yielding smaller but present benefits.

Recent DOT R-comp testing data shows this. Hoosiers run wide for their labels - these 205s exceed prior 225 street tire tread. Thus, listed rim ranges mislead. The 205s thrive on 9-inch wheels, beating 8-inch setups by 0.3 seconds.

Motorsport regulations sometimes hinder optimization, capping wheel widths directly or via tire templates. Occasionally, tires limit while wheels do not.

Our Triple Threat Miata encountered this in SCCA C Street autocross, legal for Time Trials Sport. Restricted to 7-inch wheels, we could adjust diameter by one inch. For autocross, tall tires minimize shifts, so 225/45R17 with 7.9-inch tread craved wider rims. A tall 205 might match pace, but no suitable option exists.

For track work, shorter tires aid acceleration. The 205/45R16 gained a full second over taller 225s, plus 24 pounds less rotating mass and nearly an inch lower center of gravity.

Does smaller wheel diameter help too? Data provides insight.

Final Triple Threat ND note: larger wheels and tires?

Abandoning C Street for Time Trials Sport 5, we fitted max 245/40R17 on 17x9 wheels, gaining 0.7 seconds via superior corner speed despite gearing and weight penalties.

Next fender-fill urge? Check wheels first. Maximizing current tires? Consider wider wheels. Room for both? Ideal upgrade.

Rules blocking? Innovate within limits. Width matters, but gearing and weight do too.