After an airliner touches down, why do wing spoilers help the wheel brakes slow it down?

Answer: They load the wheels

They load the wheels ✓ — Right. Spoilers kill much of the remaining wing lift, so more of the airplane's weight sits on the landing gear. That lets the tires press harder into the runway and makes wheel braking more effective. SKYbrary notes that timely spoiler deployment is especially important because spoilers directly improve brake grip.

They blow air forward — No. Spoilers are panels on top of the wings; they do not stop the airplane by blowing air forward like an engine system might. Their trick is less visible: they spoil lift, shifting weight from the wings to the wheels. That turns a flying machine back into a ground vehicle that brakes better.

They cool hot brakes — No. Brake heat is a real operational concern, but spoilers do not mainly help by cooling brakes. They change the load path: less lift on the wings means more normal force on the wheels. That is a transferable physics idea too: friction capacity depends on how hard two surfaces are pressed together.