On wet wheels it dilutes the product making it less effective, they demo'd the other wheel cleaner - clean wheels (the stronger cleaner)on alloys that were damaged already and that was used dry as well. The tech did say though that they offer different advice as to what the boffins state. The glass polish is another example he advised not to let it dry to avoid the white chalkiness flying about, and this works far better but it contradicts the bottle
I have to say though i use custom wheel cleaners trade version and I use it on wet wheels.
