I have 2 different tires on the back because that is how the car came. Why do you say the Yokohama tire is shot? The tread ware is even and the depth of the tread is very good. I don't think the ride is bad because of the rear tires. The ride is back from the front. When I hit a small crack or a pot hole it feels like the car has no suspension.

 

the tread depth based on those pics is not that great compared to what they look like when new. All in all the ES100 are junk, you would be well served to buy a complete set of new tires...treat the car right! Always have to be concerned when someone tosses is on a set of mismatched tires just to sell a car. Often times it's a clear indicator that they didn't care for the car when they had it, and thus are looking to just dump the issues onto the new buyer for the least amount of effort.

As for the noise, I presume you noticed this when you test drove the car originally? 2003 struts were nothing to write home about in the first place and you might just have a "tired" car with 58k hard miles on it. I'd take this opportuning to invest a small amount of money into the car with some good shocks (Bilstein would ride very nicely, as do the Tokico). Would be a good chance to lower the car at the same time with a set of quality springs, to make it look and behave like it should, and reverse the fate the previous owner started.

 

Dude,

I would get 2 new back tires....check out these. I had them and liked them on my stock rims, but sold them.

http://www.tirerack.com/tires/tires....+Pole+Position

Also it wouldn't hurt to have the cambers aligned.

 

Like the guy mentioned a while back. NT555's are junk (I didn't know this before) and the AVS ES100's are junk (I know from experience).
Purchase new tires all around and the car will feel completely different, a lot smoother, and quieter.

http://www.tirerack.com/tires/tires....1=yes&place=10

Those are what I have on my Z. Amazing tires.

 

Now, this is what we'd rather hear you say: "Wow, and I was actually thinking about getting an alignment and two new good tyres, or even better a full set, so I have safe rubber on the road".

Have to agree with both of Adam's posts + 100000!!!