19s or 20s?

[re-rx7]

Originally Posted by Steve Only heavy cast wheels will hurt performance. There are plenty of quality wheels out there to choose from in a 20 diameter that are lightweight. My car is a perfect example of that. In my opinion, 18's are way too small for these cars due to the size of the large fenderwells. 18's are just too small to the point almost look like a spare tire. These new 5.0's are quite large cars especially when compared to the fox 5.0's back in the day where 17's were the norm or a custom wheel was an 18 to fill the fenderwell. When it comes to wheels, it's especially true, you get what you pay for. If you buy a "cheaper" wheel, it's going to made cheaply using cheaper, heavier materials.

Larger wheels also affect the gear ratio. 18's are to small in your opinion but with a drop it looks perfect to me. 20's just look too big.

[Grandpa]

Originally Posted by re-rx7 Larger wheels also affect the gear ratio. 18's are to small in your opinion but with a drop it looks perfect to me. 20's just look too big.

Unless one is a major track whore, the minimal changes to the gear are hardly noticeable. Only stockish cars would really notice it. If you any kind of decent power its not even noticeable.

[kn7671]

Originally Posted by re-rx7 Larger wheels also affect the gear ratio.

Wrong. Wheels have absolutely no relation to gear ratio.

Tire diameter effects gear ratio, but you can choose tires for larger wheels that have an equal tire diameter as stock 17, 18, or 19's in 20" sizes without affecting gear ratio.

That being said, if you choose tires with different diameter than stock, say approx. 3/4" shorter or taller, the effect on gear ratio is minimal, about 3% on average. At 70mph you'r speedometer would be about +2mph with smaller tires or -2mph with larger tires.

Originally Posted by jng2985 20's offer more tire choice's, but a loss of power.

You don't lose power if the overall weight of your 20" wheels/tires are the same overall weight as the stock 18" or 19" wheels/tires, which isn't too hard since the factory wheels are usually on the heavier side.

Originally Posted by re-rx7 Why not just a nice set of 18's with a 1'' drop all around? Nice and subtle.

Agreed, the right 18" wheels can look nice, but you need to know what your plans are for the brakes, as more of the 18" wheel choices will not work with the larger 14" Brembo brakes, or other big brake kits.

Originally Posted by JDBishopArts The whole 19" and 20" staggered never made much sense to me.

The Corvette has done this since the C5 in 1997. Other car high performance car manufacturers do this as well, so apparently there is real benefit when tuned and setup. Just because it doesn't make sense doesn't mean we should fear it.

[re-rx7]

Originally Posted by kn7671 Wrong. Wheels have absolutely no relation to gear ratio. Tire diameter effects gear ratio, but you can choose tires for larger wheels that have an equal tire diameter as stock 17, 18, or 19's in 20" sizes without affecting gear ratio. That being said, if you choose tires with different diameter than stock, say approx. 3/4" shorter or taller, the effect on gear ratio is minimal, about 3% on average. At 70mph you'r speedometer would be about +2mph with smaller tires or -2mph with larger tires. You don't lose power if the overall weight of your 20" wheels/tires are the same overall weight as the stock 18" or 19" wheels/tires, which isn't too hard since the factory wheels are usually on the heavier side.

At that point you will sacrifice ride quality. Thats why if the car is lowered 18's seem to work fine.

[kn7671]

Most people don't realize that the Mustang comes with several different diameter tires, spreading over 1.1" in difference.

V6 with 17 = 28.0"
GT with 18" = 27.2"
GT with 19" A/S = 27.7"
GT with 19" Brembo = 27.2"
Boss 302 rear = 26.9"
GT500 with 20" rears = 27.9"

In this regard, if you had a normal 245/45R19 (27.7") All-Season equipped GT, which is .8" taller than the 285/35/19 (26.9") rears on a Boss 302, and then jumped to to a 20" 285/35R20 rear tire (27.9") would give you .4" shorter sidewall than the stock 19" AS tires, but a 100% equal sidewall height to a Boss 302 rear tire.

Additionally, the 20" tire at 27.9" rear tire will give you a better ride than the 26.9" rears, while giving a little more overall grip from a slighty larger contact patch.

[Grandpa]

Originally Posted by kn7671 Most people don't realize that the Mustang comes with several different diameter tires, spreading over 1.1" in difference. V6 with 17 = 28.0" GT with 18" = 27.2" GT with 19" A/S = 27.7" GT with 19" Brembo = 27.2" Boss 302 rear = 26.9" GT500 with 20" rears = 27.9" In this regard, if you had a normal 245/45R19 (27.7") All-Season equipped GT, which is .8" taller than the 285/35/19 (26.9") rears on a Boss 302, and then jumped to to a 20" 285/35R20 rear tire (27.9") would give you .4" shorter sidewall than the stock 19" AS tires, but a 100% equal sidewall height to a Boss 302 rear tire. Additionally, the 20" tire at 27.9" rear tire will give you a better ride than the 26.9" rears, while giving a little more overall grip from a slighty larger contact patch.

And there you have it. Solid post sir.

[Dan12GT]

18s are definetly noticeably smaller when comparing to 19s and obviously more noticeably with 20s. I myself am tempted to go the 18s route on the Forgestar FR5s I want buy, but in the future want to go big brake as well (brembo at a minimum) and don't want to have to deal with getting different wheels again. I just hate how 19s are such the odd cat with tire selections and 20s are EXPENSIVE!

[Dominic Toretto]

Originally Posted by kn7671 The Corvette has done this since the C5 in 1997. Other car high performance car manufacturers do this as well, so apparently there is real benefit when tuned and setup. Just because it doesn't make sense doesn't mean we should fear it.

+1

All the high performance cars use a staggered wheel fitment. Corvettes, Vipers, Ferraris, Porsches etc. Even the GT500 comes stock with 19s front and 20s rear.

As others have stated, wheel weight makes the most difference for unsprung weight. TSWs Nurburgrings are excellent. I saw one member on another forum with a 19X9.5 TSW N that weighed 22lbs. In that size is it definitely lighter than stock AND allow for a larger brake kit. Also on those other cars, because the front fender of those exotics are generally much shorter than the rear fenders, if they ran same size front and rear wheels, the fronts would look bigger.

-Alex