ok, I know that these two probably have nothing to do with eachother, but I have been asked to find out anyways.
Does the size of your rims...or tires rather, decrease the stability or any other aspect of the car.
For instance if someone put 18" rims on a car with stock 16" rims, would performance in any way decrease. Thanks for your time

[GTRaptor]

Depends more on the tire profile than the wheel size.

A 16 rim with tall sidewall tires say 60 will "loose" against a 17/45.

The taller the sidewall the more the tire "flex" on cornering.
The tire gets pushed to the inside of the corner and the rim wants to go out

Performance tires will always have a small sidewall.
For "comfort" (not performance), taller sidewalls are the way to go.

[dmark101]

also consider the weight of the new wheels. that will decrease or even increase the overall performance, depending on the wheel you purchase. racing wheels are extremely light as opposed to other aftermarket wheels.

i have a set of 00 R wheels on my cobra. i know they're a bit heavier than the stockers, but they perform better due to their wider track when i autocross or road race the car. on my probe, the 17's are much heavier and decrease the overall performance due to the added weight and rotational mass.