The science — how it actually works
Water-based vs solvent-based is the whole story. Solvent (silicone-oil) dressings dissolve into the rubber, throw a very wet gloss, and are the ones that fling black spots up your freshly cleaned paint on the first roundabout. Water-based dressings deposit a polymer/silicone emulsion film on the surface — a satin finish, far less sling, and no solvent leaching into the sidewall.
The brown foam is not dirt. Tyres contain anti-ozonants and waxes that migrate to the surface by design, protecting the rubber from UV and ozone cracking. That's "blooming." Scrub a tyre and the brown suds you see are those compounds coming off. It's why an unprepped tyre looks tired again within a week — you're dressing over bloom, not rubber.