I've been using these brushes for many, many years. I've never had a problem with scratching and I'm fairly paranoid too. The reason I don't use household sponges/brushes (and even several "automotive" brushes) is they typically have metal underneath all the bristles or sponges. I'm PARANOID about the brush wearing out and scratching my wheels.
BTW, if you want REALLY clean wheels especially the barrel section then I have three words for you . . . Meguiar's Wheel Brightener. This stuff is SO POWERFUL. I also have the Poorboy's Spray & Rinse, but it's not as powerful and is much more expensive than the Meguiar's. I recently helped a friend detail his Boxster S with 5 spoke wheels. I whipped out the Wheel Brightener and started spraying. Then I start scrubbing the barrel section with the Griot's brush. He says "don't bother you'll never get that part clean." I gave the barrel a quick once over with the Griot's brush then rinsed off the Wheel Brightener and he looked like this . . . :wow: The entire wheel was cleaner than he'd ever seen it. This includes the barrel area.
The reason I don't use [something like the Quickee].. is they ..have metal underneath ..[the]..sponges. I'm PARANOID about the brush wearing out and scratching my wheels..
Repeating myself here in agreement with Mikeyc, this danger cannot really be overstated. You simply *must* toss them before they wear and be very careful how you use them. The metal loop is such that you *can* use it without marring, but not if you're gonna be (even a little bit) careless. Worth the risk for me, but then I've been using them forever.
Even if you're not gonna accept the risk on your wheels, they're great for wheelwells. Just note that the same caveats about scratching apply to painted surfaces in there too.
Twitch- Heh heh, yeah the EZ Brush *does* spray nasty liquid all over