Here's Wiki definition:
A tire iron
(also tire lever
or tyre lever
) is a specialized metal tool
used in working with tires
Tire irons have not been in common use for automobile
tires since the shift to the use of tubeless tires
in the late 1950s. The term is occasionally mistakenly used to refer to a lug wrench
(esp. US),[citation needed
] which is included along with a spare tire and jack
on most new cars.
Tire irons usually come in pairs, or threes, and are used to pry the edge of a tire away from the rim
of the wheel
it has been mounted on. After one iron has pried a portion of the tire from its wheel, it is held in position while a second iron is applied further along the tire to pry more of the tire away from the wheel. This allows enough of the tire to be separated so that the first iron can be removed, and used again on the far side of the other iron. Alternating in this way, a person can work his way all the way around the tire to fully remove it from the wheel, in order to reach the tube that sits inside.