Hot Tire Resistance

Why coatings lift under hot tires, and why this one does not.

Hot tire pickup is the failure people have usually seen with their own eyes: a patch of garage floor coating lifted off in the exact shape of a tire. It is the first thing anyone asks about, so here is what causes it, and what in this system bears on it.

What actually happens

A tire driven any distance gets hot. Rubber that is hot is softer and tackier than rubber that is cold, and the plasticizers in the compound become mobile. You then park, and the hot contact patch is pressed against the floor under the weight of a corner of the car for hours.

Two things happen while it sits there. The soft rubber conforms into the surface texture, and the coating softens under the same heat. As the tire cools it contracts and stiffens, and it grips whatever it has settled into. When you drive away, that grip is applied straight upward to the coating.

The coating then loses in one of two ways. Either its bond to the concrete is weaker than the tire grip, and the film comes away from the slab. Or the film is not strong enough in itself, and it tears, leaving part of it stuck to the concrete and part of it stuck to the tire. Both are called hot tire pickup and they have different causes.

Why thin water-based coatings lose this fight

A one-coat, water-based garage floor paint has two problems at once. Most of what is in the can is carrier that evaporates, so the film left behind after it dries is a fraction of the thickness you rolled on — there is very little material there to resist anything. And a film that dries by evaporation rather than curing by chemical reaction stays comparatively soft, so it softens further under a hot tire exactly when it needs not to.

What is different about a 100% solids system

Nothing evaporates. Every layer is 100% by weight solids, so the film is the material. Coverage is arithmetic — 1604 ÷ mils square feet per gallon, so the body coat lays down 100 sq ft per gallon at 16 mil — and the thickness you apply is the thickness you keep.
It cures rather than dries. The film is a thermoset network built by reaction, not a deposit left by evaporation. It does not re-soften on warming the way a dried film does.
It is hard. Shore D 72 to ASTM D-2240. A hard surface gives a hot tire less to sink into in the first place.
There is a great deal of it. The clear topcoat alone goes down at 12 mil nominal, over a pigmented body coat, over a primer at 5 mil nominal. A departing tire pulls on whatever film is there, and a one-coat paint leaves single figures of mils to pull on.

Where this claim comes from, since there is no ASTM test for it

Hot tire pickup is not an ASTM line item on any of the five data sheets, and it is not one anywhere else either — there is no standard method for it, so no coating on the market has a test number to show you. What exists instead is the manufacturer’s position on their own product, and Duromar have given us theirs directly: No hot tire pickup.

That is a manufacturer’s statement rather than a laboratory result, and it is worth knowing which one you are reading. The properties above are the published, measured evidence that bears on the same mechanism. One related figure we still do not hold: no pull-off adhesion figure on file.

The two things that decide it, and both are yours

In practice, hot tire failures are overwhelmingly not chemistry failures. They are preparation failures and cure failures, and both are in the installer hands.

Preparation. The tire pulls on the bond between coating and concrete. A film applied over a sealed, polished or contaminated slab has a poor bond no matter how strong the film is, and the tire will find that out. The manufacturer specifies abrasive blasting, shot blasting or grinding, with acid etching acceptable only in some cases. This is the step that decides this page. What preparation involves.
Cure. A floor driven on before it is cured is a floor whose network is still forming. The base coat gives 10 hours to light foot traffic and 120 hours to full cure, and a cold garage takes longer. Before a vehicle goes back on it, the number that governs is the topcoat’s full service: 5 days. Hot tires are the hardest thing a new floor meets, so this is the wait worth keeping.