Another post above kind of describes what I mean. It doesn't seem to get in there and start turning brown like others I have tried. With a brush, it just moves around without really doing anything. Tuf Shine, Bleche White, and others start pulling out dirt and dressing before I even start brushing.
That's strange, I always get brown to come off the tires before I even scrub. Try applying it to a dry tire. If you wet the tire first it will dilute the apc and won't be as effective.