Treadwear ratings are determined by each manufacture. A 140 rating from BFG is not necessarily the same as a 140 from Khumo.
From Tire Rack
"
When looking at UTQG ratings it is important to realize that the Department of Transportation does not conduct the tests. The grades are assigned by the tire manufacturers based on their test results or those conducted by an independent testing company they have hired. The NHTSA has the right to inspect the tire manufacturer's data and can fine them if inconsistencies are found. While most new tire lines have their grades established when they are introduced, they are allowed a 6-month grace period to allow the tire manufacturer to test actual production tires. Once a grade is assigned it must be branded on the tire's upper sidewall and printed on its label.
Unfortunately, the rating that is of the most interest to consumers is the one that appears to be the least consistent. While the Treadwear Grade was originally intended to be assigned purely scientifically, it has also become a marketing tool used by manufacturers to help position and promote their tires."
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=48
Choosing a tire based upon tread rating makes as much sense as choosing a wife based upon Breast size. There are so many other important factors to consider and you should only consider tread rating comparisons between the same brand of tire.
Take for example two Khumo tires. The 712 and the SPT. The 712 has a treadwear rating of 280 and the SPT 320. By those numbers and your logic of treadwear ratings the 712 is a grippier tire and will wear out sooner. Let me tell you, the 712 is a piece of garbage and Khumo will do the world a favor when it is gone. I have owned at least 4 sets of the 712 and hated every time I bought them. Wheras the SPT is an excellet tire with much better grip and water pumping ability.
You might ask, why the disparity? Well, first look at the tread design. The 712 is designed more like an all season tire and has a ton of siping. This creates a serious problem for initial turn in and rapid transistions because it creates flex in the rubber. However once they have reached a constant radius they grip very well. The SPT on the other hand has an old school block tread design. Makes it great at transistions and turn in. It also has large water channels and works great in the rain.
From owning both sets it feels like they have simular sidewall construction as they are both stiff tires. Especially compared to the 711 that has a great tread design but a horrible sidewall. The 711 is another tire that looks great but heavily dissapoints.
The fact is, if you drive really hard plan on replacing your tires every 12 - 14 months no matter what tire you buy. If you don't drive hard on the street then buying the RE-01 is not a good investment IMO. If you want something better than the SPT but less than the RE then look at the Khumo MX.
Those things will stick like epoxy. BTW why did you leave a UIM manifold in my garage?! Punk!