Tires: Hairline Cracks in Tires, Tire Cracking

Question
My tire dealer inspected my tires and saw hairline cracks all over the tread area and some on the sidewalls.  All 4 tires are about 4 years old.  The tread was still good.  He said I should get new tires because of the possibility of blowouts because of the cracks, which I did.  He said such cracks are a major cause of blowouts.  I'd rather be safe than sorry.  I feel he was being sincere.  Was he being overly conservative?  What is your opinion?

Answer
Sarah,

I can't make an assessment without looking at the cracks.  Superficial cracks might be OK, but it depends on where they are - and the detail is important.

Rubber degrades over time, and one of the ways this gets exhibited is by cracking.  The cracks are caused by the oxygen in the air attacking the hydrocarbons in the rubber - and then the tire is flexed and a crack is the result.  However, a tire that is merely old might not have cracks and still be a problem, because not enough revolutions have taken place for the crack to develop.  

The more inflation pressure maintenance (monthly pressure checks) you've done to the tire, the less likely small cracks are something to worry about - if the cracks are superficial.