Tires: Sidewall cracks, passenger car tires, passenger car tire

Question
How bad can cracks be, before a passenger car tire should be replaced?

My Town Car has had cracks high on the sidewalls & all the way around on all 4 tires for at least a couple of years; The cracks don't appear to be getting worse.  The tires are about 6 years old, but have a lot of tread left, because the car only gets about 2,000 miles/year, mostly towing a boat (5,000 GTW).

I live in Michigan, which means that the tries should otherwise be good for another 4 years going by your other responses.

I've found RV tire recommendations that tires should be replaced if the crack is more than 2/32 deep.  Is there a similar recommendation for passenger car tires?

Thanks

Answer
Armand,

Cracking is a hard area to judge, because there are several different causes, and therefore, several different reasons why and when a tire should be removed, but the cracks look very similar.

First, you need to assess for yourself if you've done a good job of maintaining the inflation pressure.  If you've always had within 2 or 3 psi of what the placard calls for, then the cracks are probably OK.  If not, why not be safe and replace the tires?

Another thing to look for.  If there are cracks on the surface of the tread - the part that actually touches the road surface - then remove the tires immediately.  If there are cracks in the grooves - well, those cracks might be normal, but again it is difficult to judge without knowing the history of the tire.