Rick just to be clear your chain measured under tension at 256 mm across 17 pins would be about 0.75% stretched. At 20,000 miles and the same rate of wear that gives you about 4,000 miles if you replace at 1% stretch or 8,000 miles if you replace at 1.25% stretch. I replaced my original Honda chain at 1.5% stretch that's 258 mm and was at 26,581 miles, yes I keep a record of all these things.