Ideally you should use the pressure recommended on the door jamb whether using stock or Shelby tires.

If you have stiffened the suspension, drop the pressures a few pounds if required for a more comfortable ride on the street. If you are a track-day dog, you probably will be experimenting with pressures all over the map. But for occasional track days or high speeds, up the cold pressures 5 pounds or so. This will reduce tire flexing and subsequent over heating. At higher speeds your tire pressures will run about 40 to 42 pounds hot.

I suspect the lower pressure for the convertable is because it gives a softer ride and less chance of developing rattles.

Cheers.

 

The softer ride guess is totally wrong.
It has to do with weight and loading only.
And dont go by the MAX inflation pressures
on the sidewalls either.
Thats another wide misconception...

Door jamb tire pressures are for the load range tires that are on the vehicle OEM.
Switch to Shelby tires and you need to run door stickers pressures
on a shelby door jamb.
The GT door sticker pressures go out the door when different load
range tires are employed.

 

Well, if the tire pressures have to do with weight and loading as you suggest, which I believe also, then the pressures for the heavier Shelby must be different that that of the GT. So how can justify the same pressures on the GT. Where does one find the proper pressures for a GT with Shelby tires. You may be correct but I can't see the logic. Just trying to get my head around it.

By the way, I do run the take-off Shelby wheels/tires. I run the same tire pressures as before street, (30 psi) and road course ( 34/32 psi ), and see no adverse effects except the car corners better with the wider tires.

I am ready to corrected if need be.

Cheers.

 

I run 28 in mine!

 

Quote 157db:
"Door jamb tire pressures are for the load range tires that are on the vehicle OEM."

That may be true. However does not the manufacture take into account other factors when posting recommended pressures. Such as a plush ride/better handling. Or maximum contact patch area for even tire wear. Or higher pressure for a smaller contact area for better CAFE figures. Loading the car up with gear, the recommendation is to increase the posted pressures to regain the original contact patch size for the designed handling traits. I think the manufacture has some room to adjust the recommended posted pressures in order to obtain the desired trait and still stay within the tire's load range.

I could be wrong.

Cheers.