Tires: Replacement, inflation pressures, when to replace tires

Question
Is there a general rule on when to replace tires?  Mine have about 50,000 miles on them show some wear on the edges, but otherwise don't seem to cause any problems with handling. With winter arriving, I was wondering if it is time to replace?

Thanks for your advice.
Joe

Answer
Joe,

There are a number of situations that would indicate time to replace your tires.

1)  The tread has worn to or below 2/32nds of an inch tread depth remaining.  This is the legal minimum.  There are worn bars that will appear in the grroves at that depth to assistance in this determination.  If the wear bar appears in ANY loaction, it is legally worn out.  However, these bars do not appear in the shoulder of the tire and it is possible for the the shoulder to be worn out and still have plenty of tread in the center.

2)  When the performance of the tire degrades to the point where it becomes potentially dangerous.  For example, hydroplaning resistance is a function of tread depth and as you approach the wear out point, the hydroplaning tendancies will increase.  I think this starts at about 4 /32nds.

3)  If a tire starts to vibrate, it might indicate a separation starting to develop.  Since it doesn't take much distance from the time the vibration appears until the separation actually becomes visible and / or dangerous, it is important that this be taken care of ASAP.

4)  If a noise or a vibration appears, you might have irregular wear.  Irregular wear is caused by misalignment and aggravated by low inflation pressures and lack of rotation.  The peoper action in this case is to get an alignment, rotate the tires to a different position and hope the new wear pattern erases the irregular wear, however, the irregular wear might be so bad that this won't happen, in which case replacement is the only option.

Hope this helps.