Bad move.

 

Not sure about offsets but you could probably use spacers. The rear tire there is 27 inches tall assuming it is a stock sized gt4 tire, you would need new tires that match or try to squeeze that on with the front drive removed. The new smaller tires would be really low profile which may or may not work for you. The 996 has smallish wheel wells so IMO the 20's look deliberately oversized. Stebo has some 20's and likes them though.

 

I'm stock ride height though. I dont like driving slammed cars... and I dont have to worry about curbs or inclines at all in my baby. And NO it doesnt look like a monster truck either! Lol. I get many compliments on the setup.

Here's the fitment I'm running:

20x8.5 et +45 245/30/20
20x11 et +47 305/25/20

I could even add a spacer to my rears, if I wanted. Theres plenty of room if I wanted to move them out some. The fronts sit perfect.

The number one thing I would do is verify the offsets, which will be stamped into the wheel somewhere. Get pics of the offset (or whatever level of confirmation you're comfortable with) and we can help you from there.

I forgot to mention that I've had these on for 4 years and previous owner had them on for who-knows-how-long before that!

 

Sooooo I just remembered that I have the promo book for the gt4 and the OEM wheel and tire package is specified. Pics below. They are as follows:

20x8.5 et 61 245/35/20
20x11 et 50 295/30/20

So what does that mean, right... looks like you could run them (on stock suspension settings) with 15mm spacers in the front. The backs are probably fine, but you could space them out anywhere up to 17-ish mm maybe more. I would try them on then go from there... but yeah you could certainly run them with the right spacer and tire setup.

And I would have to use a tire calculator to determine the overall diameters of front vs back, but the rule of thumb is to make sure the fronts are TALLER than the backs. Mine are pretty close to even, and I havent had problems but others have warned about taller rears blowing the front diff.

Guys feel free to correct me on any of this. I am just comparing to my setup.

 

20"s are big for the 996 but certainly work, I've run a set of wheels I had kicking around, key is good quality coilovers/dampers and life is good...
based on offsets ^ spacers are needed but should otherwise work

 

Agreed. That's why I went with the smallest overall diameter I could get. My tire choice makes my setup a +1 despite the fact that my rims are +2.

I just used Discount Tire's online calculator. This gt4 setup is 1" taller than my setup at all 4 tires. Which means your ride height will be 1/2" higher than mine (unless you have supension mods) and the diameter ratios are basically identical so I believe you'll be fine. Also your clearance between tire and fender wells will be different than mine. I cant speak to that specifically. But worst case scenario, you just get new tires.

Do your due diligence, check all my math and verify for yourself... but my gut tells me you're looking ok with some 15mm spacers in the front.

These gt4 tires are 2" taller than stock, making this a true +2 setup, so your speedometer is gonna be off too. Not sure it matters to you, just an FYI. It looks like it'll show 65 when you're doing 70. NBD.

If you have any more questions just holler.

 

 

Tire-wise, I am naturally going to recommend the tire sizes I selected for myself, as mentioned in my first response above.

Since you're lowered, that changes things a bit. I can't say with certainty what works on my car will work on yours. Too many variables, with height, camber, etc...

My main concern at the moment is that a 15mm spacer in the front may be a tad too wide to fit the front tires in the fender especially if you tuck them. Like I said above, mine sit perfect in the front (which means to me: flush in a vertical plane with the fender sheetmetal) on my non-lowered car. I'll take a closer look at my geometry when I get home from work and see if I can provide some further advice on the front spacers.

Keep in mind that I am just one resource on this and I am definitely not any kind of expert. Just a dude with a car willing to help.

Also, now that I'm this invested in your success I expect that you post pics and feedback!! Share the win.

 

Alright Charlie... I'm very glad you inquired about this because it turns out my front fenders are rolled and I never noticed. Just at the top. Lol. Its about 6" each way from top center... anyhow back to the info relevant to you.

FRONTS
You're gonna need the 15mm spacers to clear the spring perch on the inside. AND You aren't going to want them out much farther than that, especially since you're lowered. This is gonna be a tight fit. You may have to consider raising your car a bit to clear everything. The clearance between the top of my tire and the sheet metal fender is about 1.5" so you've got some leeway there. Just leave yourself enough height that you have some usable shock travel. I still think you'll be alright, if you're open to changing your ride height to make it work. I have no idea how your coilovers are setup. It all relates to how much shorter your springs are, and then how much the perch is dropped on your coilovers.

And if you dont know what I'm talking about, you should have a shop do the setup! Matter of fact you should probably do that anyway; get an alignment and corner balance at the same time... my 2 cents. Now that I think about it, there are other guys out there running 9" wide fronts. Maybe look into their experience.

REARS
Are no problem. I could probably safely space mine out 10mm without rolling fenders and 25mm if I rolled them. Maybe more.

Long story short, it can, and has been done.