How to know when timing belt change is a must?

[RacerX125]

As title states. Someone might say its a must when it breaks, but what i mean is how to check or what to check to see if changing timing belt is a must.
2003 na cruiser with 103,854 miles and has had no timing belt change before in its life.

[LionPT]

Anything over 95,000 & your pushing your luck...get the water pump & timing belt replaced at the same time.

[CREWZIN]

[rob342]

mine looked fine when it snapped. you could still read the writing on it just fine. there was no cracking or shredding, no grooves, etc.. infact the only clue that it was not new was the slight railroad-tie pattern starting to appear. after 10 minutes searching the internet, i'd say it looked similar to this

then when you'd pinch it, you'd see little cracks like this open up. unfortunately, in order to pinch it, you have to remove it anyways.

[quicksilverdon]

As Dirty Harry said, "Do you feel lucky.....?"
You are due.

[ColTED]

had my wife's PT's first TB change recently at 164K miles.....don't push your luck......It's like a ticking bomb that won't give you a peace of mind like I had for quite a time....