Is it worth the price? Is performance really that much better?

 

Huh? Don't consider performance at all. The wheel size is not an indication of performance. You'll change tires relatively frequently anyway, so stickier tires are always an option in either size.

If you like the looks of the 19in wheels better than the 18in, then get the 19's. If you're gonna switch to aftermarket anyway, then just get the cheapest wheel available.

Another thing to consider might be availability and pricing of replacement tires. Back in the day...19's didn't have a lot of choices, and they were considerably more expensive than 18 or even 20 inch sizes. However this may not still be true.

 

Choose the wheel/tire combo that gives you the stickiest tire and lightest combo.
The lightest combo lowers your rotating mass giving you best acceleration for a given HP.
Sticky tires will give you the best cornering.
You only get a slight advantage from a lower sidewall height, which is the only possible performance improvement of a larger diameter wheel of the same width.

 

 

Technically a bigger tire means a bigger surface of contact with the ground. Bigger contact means more grip. I don't know if the difference is noticeable, but according to my basic notion of physics, there must be a slight improvement in performance (grip/braking/cornering) for sure, but only if you use the same brand of tire too. Common sense tells me that you cannot compare improvement in performance from 18" Pirelli to 19"Goodyear, for example.

In terms of bang for the buck, I am not sure, cause the choice of rims and tires is smaller with 19s than 18s or 20s, and it cost more for 19s, Stupidgenuis36 was right on.

 

The actual contact patch remains largely unchanged, actually. Plus, bigger wheels and tires means more weight, which have a more noticeable impact on performance.

 

Yes. The shape of the contact patch changes much more than the area with wider tires.

To understand it, imagine tires with zero stiffness. At a given pressure, the total contact patch areas would be absolutely identical regardless of the dimensions of the tires. And the contact patches could be used to actually weigh the car. The contact patches in square inches (the SI in PSI) multiples by the PSI would be the weight of the car in pounds (the P in PSI).

But since tires are NOT infinitely flexible, a change in width or height will have some effect on the size of the contact patch.

 

I have the 20" foundry wheels as an option. I like the looks of them over all the other options. Performance? They're probably the worst.

 

Putting 19' Sve drift wheels on tuesday along with my aluminum driveshaft Ive heard they are fairly light wheel.

 

If you want your car to look like every other mustang that you see driving keep the 18s. Me for one, I like something unique and not "off the lot". I went 20s for two reasons. First they look way better and two price is pretty reasonable. Got a really good deal from AM during a wheel sale and tires from direct tire direct.