I just assembled a couple of bikes with disk brakes for the first time and it took a number of tries to get it right -- and a number of adjustments until the cables had stretched fully. Now they work just fine. I read a post from a guy who used a piece of plastic he described as "the thickness of a gift card" between the movable pad and the disk to quickly adjust the brakes. When I get a spare evening this week I am going to see what kind of "shim stock" I have laying around and give that a try. Frankly I would have designed them so that you just bolted them to the fork and used a couple of screws to adjust them side-to-side but these were the entry level disk brakes. Maybe the nicer ones have more precise adjustments.

The bikes I assembled were from Nashbar and while I was happy with the quality for the price, the documentation was poor. I've built a number of bikes up from bare frames so it wasn't too bad, but if I hadn't had that experience, I might have found the job to be too difficult. The disk brake manual was separate and much better, but it would still have been very difficult if I wasn't handy with tools.

Bob