Noisy tires on a Prius

After 45,000 miles, I replaced Goodyear originals with Firestones that are very similar except for 86T not 86S and DOT A8LX not DOT VWLX. I also had an alignment done as the original tires were wearing out along the four outside edges. The new ones are very noisy and buzzy feeling even on smooth pavement. As a hybrid,it was always so quiet but is now quite noisy. Any ideas?

Tires vary greatly in how much noise they make. Sadly, you never know how noisy or quiet a given tire will be until it’s on your car.

After a few thousand miles, the noise may diminish, I’t’s often mold flash that will wear away.

The numbers/letters you note don’t tell you much about the tires. Next time go to TireRack.com and read reviews of possible tires for your car.

As Tex suggested, the reviews at tire rack will tell you if this is common for these tires.

Tires designed to give maximum fuel economy often transmit road surface irregularities to the vehicle (buzz) but you noted that this occurs on smooth pavement as well, which seems odd.

The numbers you gave mean very little in the noise your tires make.

86T and 86S refer to the load rating and speed rating of the tires.
86 is the load rating for both tires, and T and S are different speed ratings.

The biggest creator of noise with tires is the tire tread shape.

BC.