My local Sears here in Washington doesn't carry trailer
tires and won't balance lug-centric tires.
Domenica, the thing about trailer tires is to keep them properly pumped up and avoid driving fast, especially in hot weather on hot roads.
WDH is
weight distributing hitch, which takes some tongue
weight off the rear of the tow vehicle and spreads it to the front
axle and the trailer
axle. WDH alone provides some stability but does not itself provide any sway control, however, some WDHs can have sway control built in. Equalizer provides friction sway control and Reese has a dual cam system.