PP2 tire sizes

[wtb6mtv8rwd]

305/30/19 Cup2 OD: 26.3"
305/35/19 PSS OD: 27.4"

26.3 ÷ 27.4 = .95985401
.95985401 x 3.73 gears = 3.58 effective ratio.

Switching to 305/35 PSS is almost like going back to non perf pack gearing. I'd also note that those tires are 5lb heavier each (+ 20lb unsprung weight).

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[D Bergstrom]

Guess I look at it differently. A PP1 car has the same 3.73 gear ratio with a 27.66” tall tire, so a PP2 has a 3.94 equivalent gear ratio. I am going to run a 27.13” tall tire, so a 3.86 equivalent ratio. (This comes from me having a PP1 car prior to the PP2.) Yes, compared to what I have now, 26.2 vs 27.13, I will be loosing gear, 3.60 equivalent, but that difference is only 77 rpm at 75 mph, not enough for me to care about driving on the street.

Michelin’s website lists the weight difference as 2.71 pounds between the oem cup 2’s and 305/35 pilot sports. I am going with 295/35’s, and that is only a 0.53 pound difference. Since both will be installed on a heavy ass PP2 oem wheel, I am not concerned at all.

The other reason I would like a larger tire also is because of my Automotive Authority spare tire. It measures about 27.5” in diameter. That diameter doesn’t match up well with a 26.2” tire.

Doug

 

[Mikepol2]

Force applied to the ground by the rear wheels is engine torque (let's use the max 420 ft-lbs @ 4600 rpm) x gear ratio (1st in a 2018+ MT82 car is 3.24) x axle ratio (3.73) all divided by the tire radius in feet (for the PP1 it's 1.1525) and split evenly between the two wheels = 2,202 lbs per wheel.

If we change the rear wheels from the stock 275/40-19 PP1 rears to the 305/30-19 PP2 rears, which as listed above in post 16 have a 26.3" diameter, the road force increases to 2,316 lbs per wheel.

Going to the GT350 305/35-19 rears, which have a very similar diameter to the stock PP1 wheels, the road force is around 2,223 lbs per wheel.

So in effect, changing from stock PP1 wheels to the GT350 wheels has almost no impact on force applied to the road, but dropping down to the smaller PP2 sidewall increases road force by around 5%. Whether that would translate into measurable numbers on the track or seat of the pants feel on the street, who knows.

 

[D Bergstrom]

Got the new tires mounted up on the new Ford Performance wheels yesterday and got them installed on the car this morning with some Gorilla black lugs. Only pic I have so far, but will get some more once I get it out of the garage over the weekend.

Doug

 

[Mikepol2]

Excellent choice with the black wheels to go with the magnetic car.

 

[Jonyxz]

looks fantastic, you added the gt350 center caps?

 

[D Bergstrom]

Yes, I already had them. Was running them on the SVE wheels I had on my 2017 GT.

Doug

 

[D Bergstrom]

Couple of pictures after her bath this morning.

Doug

 

[HoustonGT]

Yep that was me. I actually ran the 295/35 front and 305/35 rears on both stock GT350 wheels and the PP2 wheels. Different offsets between the two. Zero rubbing with the stock suspension and the GT350 wheels. @Jonyxz is right, I did get a little rubbing in the front with the PP2 wheels but that was with a 7/8" drop spring. Now running the GT350 springs which gave me about 3/8" drop, and solid as a rock, no rubbing.

What tires?

 

[Mikepol2]

What tires?

Pilot super sports

 

[HoustonGT]

Pilot super sports

Is a 285 too narrow for the PP2 OEM front wheels? Anyone know?

 

[Jonyxz]

Is a 285 too narrow for the PP2 OEM front wheels? Anyone know?

Its perfect for a 10.5 wheel

 

[Mikepol2]

Yep according to Tire Rack's specs, a Pilot Sport 4S in 285/35-19 fits a 9.5" to 11" wide wheel.

 

[jmorris47]

Are you using the M-1007K-DC105 and M-1007-DC1911 wheels? Thank you.

 

[D Bergstrom]

Are you using the M-1007K-DC105 and M-1007-DC1911 wheels? Thank you.

Yes, I bought the kit that included the 19x10.5 and 19x11 wheels and tpms sensors, part # M-1007K-DC19XMB.

Doug

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