What is the proper speed adjustment for a tractor-trailer entering a curve?

The correct technique is to slow down before entering a curve and maintain steady speed (or gentle acceleration) through it. Braking inside a curve transfers weight forward, reduces grip on the rear, and increases jackknife risk. Accelerating inside the curve adds force that can push the trailer outward. Slowing before the curve gives you time to brake straight (when braking is most effective and safest), then carrying steady speed through lets the trailer follow the tractor smoothly. Choose your entry speed conservatively — posted curve advisories are for cars, not loaded tractor-trailers. If you have to brake hard in a curve, the curve was too tight for your entry speed.