I think the tire subject is another typical De Tomaso rabbit hole. To add to it:
I have a brownline print, that came from Ford Design, that came from GHIA.
It is 1/10 scale. It is the four views of the Mangusta PRODUCTION car. Not the show car and it was signed by Giugiaro. Dated August 10, 1964. The show car was shown with the chassis later in October at the Turin show. The production car, like mine, has very large wheel tubs for, wide race tires?
The side view drawing shows the tire size on the tires. 225X15X70 on the rear and 185X70X15 on the front. Tire information and ground height is some of the essential information required to start the drawing.
I sent two copies of the drawing to Giugiaro, one for him and one for his signature to be returned to me. They didn't read that part of my message
So I never got the return copy.
When I saw his son Fabrizzio the following January at the NAIAS he said that his dad framed it and put it on his office wall.
I would like to put better tires on my car but the 275X15X60 rears and the 235X60X15 fronts look very good on the car, fill the wheelwells in the rear and give me good road clearance. They are very good tires.
As I said I wish they rode better but that is the problem of the Michigan roads not the tires.
Regarding the speed rating, I am done driving the car over 140.
1959, while in college I put a small block in my MGTD and after getting it running my dad worried about the tires. He sent me to a tire store and I had them put 670X15X70 Something on the car, same size as the current Corvette. I went right out and drove it about 140.
The bill, for 4 tires installed and balanced was something like $16.50.
He got a discount. Scary.
Dick Ruzzin