That would seem to explain where the 15 and 17 come from in the Dayco numbering system, 15/32 and 17/32. Although I’ve just nominally measured and casually discussed them as 3/8” and 1/2” belts, when I’ve found a width reported on the Dayco chart it’s in decimal form but slightly wider than 3/8” and 1/2”. I obviously never gave a lot of thought to the widths as length was the biggest struggle in finding belts that fit. The power steering belt is the only one on my car that is 17/32.














