Re: Cold air Box 57 at 2012 Hershey Hillclimb
As I stated in post #11, the original CN72 was fabric (nylon) , not steel belting, and I assume this reproduction follows suit, but I will find out for sure when I see it next week.
Although not so-stated in the size designation, Pirelli claimed the CN72's aspect ratio was about 0.70. Including the aspect ratio in the tire size designation didn't become common until about 1968, and Pirelli included the aspect ratio in the size of the CN73, which was the CN72's successor.
From my old Pirelli Pocket Guide the 205HR-15 CN72 is speced at 26.68" OA diameter, 8.94" OA width on a 7.5" wide wheel. From this I compute a sidewall height of 5.84", and 5.84/8.94 = 0.65. The OA width of a mounted tire varies by about 40 percent of the difference in wheel width, so on a 6", wheel, which is the minimum of the 6-7.5" recommended range, the width would be about 8.34" and the aspect ratio would be 5.84/8.34 = 0.70, so Pirelli's claim was correct.
Keep in mind that the aspect ratio is an approximate dimension, and for any given tire will vary depending on the tire's actual dimension and the width of the wheel it's mounted on.
Duke
As I stated in post #11, the original CN72 was fabric (nylon) , not steel belting, and I assume this reproduction follows suit, but I will find out for sure when I see it next week.
Although not so-stated in the size designation, Pirelli claimed the CN72's aspect ratio was about 0.70. Including the aspect ratio in the tire size designation didn't become common until about 1968, and Pirelli included the aspect ratio in the size of the CN73, which was the CN72's successor.
From my old Pirelli Pocket Guide the 205HR-15 CN72 is speced at 26.68" OA diameter, 8.94" OA width on a 7.5" wide wheel. From this I compute a sidewall height of 5.84", and 5.84/8.94 = 0.65. The OA width of a mounted tire varies by about 40 percent of the difference in wheel width, so on a 6", wheel, which is the minimum of the 6-7.5" recommended range, the width would be about 8.34" and the aspect ratio would be 5.84/8.34 = 0.70, so Pirelli's claim was correct.
Keep in mind that the aspect ratio is an approximate dimension, and for any given tire will vary depending on the tire's actual dimension and the width of the wheel it's mounted on.
Duke
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