ROCKFORD, Ill. (WTVO) — Just like a pair of well-loved shoes, tires start to get worn down and eventually need to be replaced.

Many residents, however, might be wondering just how often they should be replacing them.

Six-hundred and sixty-four people died in tire-related crashes in 2020, according to the National Highway Traffic Safety Administration. The reason for this has to do with a tire’s tread. The more the tread is worn down, the less grip the tire has on the road.

A good way to test if a tire’s tread is still enough to be safe is to put a penny into one of the grooves, according to Consumer Reports. They said that “if the top of [George Washington’s] head is flush with the tread, you have about 4/32 inch of tread left.”

That is enough tread to still maintain some grip in adverse weather conditions, but it does mean that the tires are on their way out. Drivers should consider replacing their tires if there is only 2/32 inch left, , according to Nerd Wallet.

Different factors can lead to the tread wearing quicker or slower. These can include how many miles a person drives, weather conditions and maintenance. No matter what, tires will eventually need to be replaced.

There is no set requirement for age when it comes to replacing a tire, but it is generally recommended for people to replace them six years after the manufacture date.

Drivers should also remember to not drive on tires that are over 10 years old.