20" Rears, 19" Front on GT500, anyone know why?

This was optional on the 2011/12 GT500 as part of the Performance Package, but this setup is now standard equipment on the 2013 GT500's.

For those that don't know, the GT500 uses the following:

19 x 9.5 Front - 265/40/19 @ 27.4"
20 x 9.5 Rear - 285/35/20 @ 27.9"

So anyone want to take or guess, or give some insight here? I was thinking of doing something similar with the Forgestar F14's:

19 x 9" Front - 265/40/19 @ 27.4"
20 x 11" Rear - 295/35/20 @ 28.1"

 

I think as big a part as the handling comes into play with those choices, that there is also a one upmanship thing going on too.

You know, mine is bigger than yours...

 

Well I was thinking more along the lines of this. A taller rear tire, under normal circumstances, should give the car more front grip.

With the GT500 being a staggered setup, the wider rear tires should cause a more noticeable push (understeer) condition, but coupled with the taller rear tire diameter, you should get more front bite back to counteract the increased understeer.

Thoughts?

There seem to be lots of high-end rear drive sports cars doing this, adding about .6" to .8" taller tires in the rear, sometimes with same diameter wheels, sometimes with +1" diameter wheels.

 

The issue with large diameter wheels with short tires is greater NVH, ride harshness and less wheel protection due to the short sidewall, taller tires alleviating this somewhat.

Taller tires also fill the wheel opening better.

 

Just my opinion. Taller tire in rear should give more footprint on ground for traction. The wider the tires on the front the more the car tends to follow irregularities in the road; not so good.

 

kn7671 - Did you ever have any luck with what you were trying to do? Its a huge coincidence that I have also been talking to Forgestar about a set of F14s. They were also interested in my reasoning for 19F and 20R. I just said it was because I wanted to reduce the massive gap at the rear in my Boss 302, without going to shorter springs. I also wanted the 11 inch rear and deep concave wheels, but they were saying that I can only do 10.5's in the rear. I have seen other mustangs with 11 F14 rears, but I am not sure if they are regular or deep concave F14s.

As for why the GT500 has this, I was thinking it might be better with the gearing the car has. 19 and 20 inch wheels have a different revolution count right per unit time/distance? I dont know, just an idea. I just want the look for now, track tires are going to straight to business 302R/302S setup lightweight 18's.

Sarosh

 

https://themustangsource.com/f726/th...s-rear-505396/

 

Why would you go smaller in the front with just a 9" wide wheel. You can go ET45s with 19X9.5 and run a 285/35/19 front and run a 305/30/20 rear.