The world's fastest roller coaster has been found to be something of an overachiever and will get brakes to slow it down.

The Steel Phantom at Kennywood Park debuted to rave reviews Friday. Its 225-foot drop is billed as the steepest among roller coasters anywhere and its projected top speed of 80 mph is promoted as the world's fastest.But after some riders complained they were being jerked around too much, park officials timed the ride and discovered it was making the 3,000-foot looping, plunging and corkscrewing dash in 1 minute 40 seconds, five seconds faster than it should. That gave the Steel Phantom a speed of about 81 mph.

Kennywood Park closed the Steel Phantom on Sunday to find out why.

Ron Toomer, president of the manufacturing company, Arrow Dynamics Inc. of Clearfield, Utah, said computer analyses showed the Phantom was going too fast as it hit the two boomerangs, loop and corkscrew that make up the last part of the ride.

"We're still trying to figure out why," he said Wednesday.

The brakes initially will be set manually, but Arrow eventually may install sensors that would apply the brakes only when the coaster's speed tops 80 mph.

The only other option to slow the ride would have been to change the elevation of the track, a costly and time-consuming task, Toomer said.