Clarification on Wheel Rules for Stock Class

[robinsta]

Hello,

If I have a 2019 Fiesta ST, which only comes with 17x7 wheels, the only wheel choices I have are 18x7, 17x7, and 16x7 correct? I can't use 15x7 even though other models of Fiesta use that size? Thanks for the clarification, I just want to make sure I get the right wheels to stay in Stock Front.

[JWA]

That is correct, the "OEM Wheel" for the purpose of that rule is specific to the sub-model, so the ST specifically. 16x7, 17x7, and 18x7 are your options, also respecting the offset rule.

[Pete]

Specifically, the wheel size that the car was manufactured with. If your car was built with an optional 18x8 wheel, that is what you must run (barring the 1" rule).

The "fun" part is, the door sticker is not always correct. Chrysler for years put stickers on Neons that called out for 13" wheels. Probably exactly three Neons were made on 13" wheels.

[JWA]

Specifically, the wheel size that the car was manufactured with. If your car was built with an optional 18x8 wheel, that is what you must run (barring the 1" rule.

My understanding is different than that. The rule allowing entire option packages to be removed or added overrides that concept. If on a given model the manufacturer offered a choice of different wheels with different sizes, separate from any other packaged items and a window sticker option from the factory (not a dealer installed after-order accessory), then you are allowed to ”change” to any of those wheels and they would become the basis from which the 1” variance is based. Since the wheels can be replaced you obviously don’t have to have the specific wheels in your possession. So, effectively for most modern cars, you can go 1” smaller in diameter than the smallest wheel option that exact car could have been ordered with.

In the case of the Fiesta ST there was only one wheel option, the 17x7s. Using the 2019 Ford Mustang as an example, the Ecoboost model comes with 17” wheels as standard but you can choose from two 18” and five 19” standalone factory wheel options at the time of order on the window sticker. If the given car was ordered with one of the 19” wheel options, you are not stuck with that wheel size, you are free to run anything from a 16” to a 20” diameter wheel on that car in Stock class, assuming you are also still within the width and offset values relative to the target wheel size option you are using as the basis for the calculation.

[Pete]

My understanding is different than that. The rule allowing entire option packages to be removed or added overrides that concept. If on a given model the manufacturer offered a choice of different wheels with different sizes, separate from any other packaged items and a window sticker option from the factory (not a dealer installed after-order accessory), then you are allowed to ”change” to any of those wheels and they would become the basis from which the 1” variance is based. Since the wheels can be replaced you obviously don’t have to have the specific wheels in your possession. So, effectively for most modern cars, you can go 1” smaller in diameter than the smallest wheel option that exact car could have been ordered with.

In the case of the Fiesta ST there was only one wheel option, the 17x7s. Using the 2019 Ford Mustang as an example, the Ecoboost model comes with 17” wheels as standard but you can choose from two 18” and five 19” standalone factory wheel options at the time of order on the window sticker. If the given car was ordered with one of the 19” wheel options, you are not stuck with that wheel size, you are free to run anything from a 16” to a 20” diameter wheel on that car in Stock class, assuming you are also still within the width and offset values relative to the target wheel size option you are using as the basis for the calculation.

As long as you can prove that the complete option package was installed. Reprogramming the computers in the car, for instance, isn't allowed, so you could get protested on the basis of having an illegal tune if the manufacturer has a different flash in any of the control modules relative to the tire size. It's then up to you to prove that you did get the car reflashed for the correct tunes, or that the manufacturer doesn't discern for tire size in the tune. (Or up to the event officials to say, hey, it's a giant car in a sea of Miatas and E30s, it's not really relevant)

Playing the "option package" game is frought with all sorts of hazards like that.