Originally Posted by
gugie
A set of braze-ons for racks, like the hour glass shaped ones shown above, would cost you $20-25 to add by most framebuilders.
In almost all circumstances, I prefer a brazed-on attachment over clamps. Anything you clamp on will dig into the paint (or powder coat), and be a place for water to accumulate. Once that happens, you'll eventually get rust. In addition, clamps seem to be one more failure mechanism - if you're riding and one breaks, you don't have a backup plan. I almost always carry a few M5 screws of different lengths in my kit and a tiny tube of locktite.
The one exception to my personal rule is front derailleurs. A brazed on bit there will limit your chainring selection, and I've always had a difficult time adjusting them vs. a clamped on derailleur.
snip . . .
Sure everything else being equal, I'd prefer a brazed on attachment too for the reasons you gave but I still think p clamps are fine for a bike that lacks them. The p clamps I've used all have a nice rubber coating so they do not dig into the paint. Heck they're stainless steel and I don't see them failing readily. They're cheap; swap them out every other tour if you're worried about failure. Plus there are a lot of vagaries when it comes to mounting a rack; p clamps at least are adjustable.