I have seen some interesting anomolies.
If a tire is the stock tire on your car, it almost allways rated more harshly.
The same exact tires can be purchaed aftermarket - as an upgrade. The reviews are much more favorable in this case.
I am not sure why this is, but I have seen it in many circumstances.
Survey data tends to be extremely favorable on the best deal price wise in any size, sometime surpassing some of the best tires in the size for survey results. I attibute this to customer expectations.
The buyers of our best value tires may often be a commodity consumer, typicalling buying their 4-$100 local bargen basment tires.
When you buy into Tirerack's entry level tires, the quality is considerably higher then they are accoustom to. This is why the cost leaders on Tirerack get such great marks.
Allways consider the mileage reported when looking at survey data. A few survey can greatly affect the review ratings when there are less than 1 million miles reported back.
Survey data tends to even out and be more accurate once its past the million mile mark.