I have a ’06 Mustang GT that came from factory with the optional 18-inch “fan blade” wheels with BFGoodrich tires. I thought I read somewhere where Ford made slight adjustments to the suspension to accommodate the optional larger wheels. Have you or other readers heard of this? If this is true, I would keep the suspension stock, hopefully keeping the car for many years. If not, I could then consider aftermarket suspension components to install without worry.
We do not know for certain if the ’06 Mustang did indeed have minor suspension tuning changes for a specific wheel and tire package, but we have heard of Ford doing just such a thing on other year Mustangs and even other models. Essentially, Ford engineers determine that a certain wheel size (its weight mostly) or a certain tire size (harsher ride due to less sidewall) could possibly exceed the stock suspension’s tuning parameters. To bring the suspension back into “spec,” a slightly softer spring or shock might be used or even a different durometer bushing in the control arms or shock ends. That being said, these minor changes should not deter you from upgrading your suspension if you want to lower the car, improve its handling, and so forth.
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