Why do tires leave marks on sealed pavers?

The mechanism starts in the tire, not the pavers. Euclid Chemical's technical bulletin CP-22 describes tire marking, or hot tire pickup, as plasticizer migration: driving heats the tires, the plasticizers in the rubber soften and leach out, and a hot tire driven or parked on concrete sealed with a cure and seal migrates those plasticizers into the sealer or coating and discolors it.

That bulletin is written about concrete sealers and cure and seals, and the mechanism is Euclid Chemical's, not a finding of ICPI or of the Concrete Masonry and Hardscapes Association; ICPI's Tech Spec 5 for interlocking concrete pavers does not describe it.

Euclid Chemical narrows the risk to specific chemistries. Most plasticizer discoloration occurs on acrylic or styrene-acrylic cure and seals, because those polymers have minimal crosslinking; epoxy and urethane coatings are more crosslinked and less likely to mark, though it says marking is still possible on them. A penetrating silane or siloxane sealer forms no film on the surface at all and does not react with plasticizer from a tire, which Euclid names as a reason it may be the better choice for exterior concrete where tire marking is a concern.

Which sealer suits a driveway that sees daily parking, against one for a pool deck, is answered under whether driveway pavers need a different sealer than pool pavers, and how the two paver sealer families, film-forming and penetrating, differ is set out on the paver cleaning page. The product on a given driveway, and what it resists, is on that sealer maker's own label.

Tires are not the only rubber Euclid names. Rubber mats, rubber-backed rugs, garage door weatherstripping and similar rubber items can cause the same migration, and Euclid says these and other rubber items may stick or cause discoloration when left sitting on concrete sealed with a cure and seal product. ASCC's Decorative Concrete Council adds that some mat backers carry plasticizers of their own that migrate together with the sealer, even in older applications.

The cure time a fresh sealer needs, and why a surface can still feel tacky after it looks dry, are a separate question, answered under why pavers are sticky after sealing.

The words hot tire pickup also turn up in places that are not about a paver sealer, a Techniseal garage floor coating among them, and ICPI's paver document treats a tire skid mark as a stain to scrub rather than a sealer reaction. Where the term is and is not printed is set out on the hot-tire pickup glossary entry.

Cleaning an existing tire mark off a paver is a separate job from why it appeared, covered under whether tire marks can be removed from pavers.