I flatted the stock rear tire tonight. Local DPW chipped a six-inch wide section out of a poured concrete bikepath and I didn't see it until I was on top of it. Just a little pinhole, but flatting always makes me sensitive to how the tires feel for a awhile afterward. Even at 70lbs, the rear felt like it was flatting again, even though every time I checked it it was just fine and still sitting at the 70lbs I had put in it- I think being sensitive to the tire feel just made me realize how much of my weight is on the rear-I'm guessing 80%+.