So I've just bought 2 new Pirelli Scooter Angels for my GTS. The front is std size 120/70-12, but the rear I bought is 140/70-12 and I'm trying to derive the circumference of the std 130/70-12 to determine the ratio change (i'm just being overly curious)
I took a cloth tape and measured the circumference of each. 120/70-12 came out as 1415 mm and the 140/70-12 is 1535 mm. If I take the two and average them to split the difference, that comes to 1475 mm for the 130/70-12. With those assumptions, I can tell you that the circumference of the 140 is 4.06% greater than the 130.
But I'm fairly certain it's not that simple. Mathemetically, you can take the diameter of a circle and multiply by 3.14 to get the circumference. But I don't have a way to measure the 130/70-12 tire
Ultimately, I'm trying to determine improvement in mileage and top speed by moving from the 130 to the 140 in the rear.
I'm certain there is someone who can help me out here.
Thanks, Carl