Tires: High speed intermittent hum on tires

Question
Hi, I own a 2011 CRV EX-L AWD with Michelin Defenders (23600 miles).  Overall CRV has 43000 on it.  Recently in the past 5K or so at highway speeds (55+) and after 15-20 min of driving, when going road goes to right, there is a loud hum that starts.  When the road straightens or goes left, the noise stops.  It started on the front (sounded as if driver side).  I had them rotated (22500) and the noise followed to rear.  Since I've had them I have them regularly rotated and I also get an alignment check every spring as the roads in Buffalo are rough.  Any ideas and if I need to replace them, can I just replace the rear two or do I need to do all four.

Thanks,
Marc

Answer
Marc,

It sounds like your tires have developed irregular wear - and the problem is the alignment spec in the rear = more than a degree.  That spec tends to wear tire unevenly, but develop good cornering power.

I would recommend you get an alignment that minimizes the camber - an ALL positions and ride it out.