The Army (search) says it has uncovered many problems with its newest troop transport, a combat vehicle first put into use in Iraq.

A study of the Stryker's (search) performance in Iraq found numerous design flaws and other problems. For example, the 19-ton, eight-wheeled vehicle bogs down in mud and the engine strains when 5,000-pound armor is added to protect troops from insurgents' explosives.

The armor's extra weight also is causing problems with the Stryker's automatic tire pressure system, requiring crews to check tire pressure three times a day, according to a report from the Center for Army Lessons Learned.rom December that was made public Thursday by the private Project on Government Oversight.

"The Army should not put inadequately tested equipment in the field, as it creates a false impression that the troops are properly equipped to fight in combat," said Eric Miller, who investigates defense issues for the oversight group.

Maj. Gen. Stephen Speakes, director of Army force development, said the Stryker has been "extremely reliable" since it went into action in October 2003.

He said the effort to review performance and get suggestions from troops using the Strykers is "exactly what we in the Army expect" when deploying a new system.

"When we field a system it's never perfect," Speakes told Pentagon reporters Thursday after the report became public. Some of the problems will be fixed by the summer of 2006, he said.

There are 311 Strykers in Iraq. The $7 billion Stryker program is intended as a stepping stone to the ultimate goal: a high-tech family of fighting systems known as the Future Combat System (search), which is expected to include unmanned ground and aerial vehicles.