Tires: Tire Noise, directional tires, mechanic shops

Question
I have Bridgestone Potenza's on a 2002 Mitsubishi Eclipse. The first set I bought were a little pricey but HEY...they lasted 90,000 miles. I was very pleased with this, however, as the tires got older they began making a noise. I had my mechanic look at it because I thought it was a bearing. It wasn't! Firestone told me directional tires begin to make noise after they begin to wear. When it was time to buy new tires I decided to buy the same ones since the first set were guaranteed for 50,000 miles according to the manufacturer and I pulled 90,000 and had tread remaining. I now have 60,000 on my second set and again, there is a tremendous amount of noise when you pick up speed and the faster you go the louder it gets. Someone else had written in about this problem and was told to have the car checked out for an alternate problem. My question is...why do directional tires do this? It is very annoying and for my next set I am not so sure I want directional tires. Traction is EXCEPTIONAL...AA rating...but the NOISE!!! OMG!!! One idiot at Firestone told me the only reason directional tires make noise is if the suspension is weak and once the tires start to chop they never stop. My suspension is fine so I think he was trying to make some extra money for the company AND make an idiot out of a woman who grew up working on cars with her Dad...Wrong thing to do! I lost confidence in the tire store after he told me that. WOMEN beware of men at auto mechanic shops who want to take you for an idiot. Not all women are car stupid. I would really like to know if all directional tires do this and if so...why? Thank you for your time!

Answer
Jean,

First, ALL tires do this - directional, non-directional, asymmetrical, symmetrical.  Some tires are more susceptible than others, but none are immune - and it is caused by misalignment with insufficient rotation practices and insufficient inflation pressure aggravating the problem.

What is really going on is irregular wear and it becomes apparent in 2 ways - noise and / or vibration (but those are really the same thing, just a difference in frequency.)

So if you got 60K out of 50K tires, you did great - and I think the lesson here is to stick with what works.