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The Pro-Am Class is another class where professional drivers are not allowed, but the rule set for the cars is pretty wide open. This gives amateur drivers the opportunity to build their cars exactly how they want without having to worry about strict rules, while evening the playing field by not allowing professional drivers. The Pro-Am class gives teams the opportunity to replace all glass with lexan and also allows for the the use of composite/carbon materials. The minimum weight is ~2,645 pounds (1,200kg) or factory weight minus 20%. 
The Pro-Am class was introduced last year and it has attracted some impressive builds, like the Tilton/53-Thirsty Honda Civic. Engine modifications are unlimited and sequential gearboxes are allowed. The spec tire for this class is the Advan A050. Again, the only difference between this and the Pro Class is the restriction on professional drivers.
This year a new one-make class is debuting for the R35 GTR. This new class will have Pro and Tuner sub divisions. The R35 GTR Pro Class runs under the same rule set as the world renowned Pro Class, with the exception of the spec tire which is the Yokohama A005 instead of the Advan A050 that the non-GTR Pro Class runs. The R35 GTR Tuner Class does not allow for elaborate aero or body modifications, but engine modifications are pretty wide open as long as the displacement of the engines remain under 3,800cc. Just like the Clubsprint Class, professional drivers are not allowed and the cars must be street registered. 
The Open Class is quite unique as this is where skilled amateur drivers and privateers can test their skills against professional drivers/tuners. Though it may seem that aero is wide open, it has some very specific restrictions. For example, vehicle width (excluding mirrors) can extend past the original body lines but only by 250mm. Lexan is also allowed in this class though the original glass windshield must remain.
Engine modifications in the Open Class are unlimited and sequential gearboxes are also allowed. This open rule set has resulted in the largest field out of all the WTAC classes. It's truly awesome to see the large variety of cars in this class. This year we saw everything from a FWD Integra to this beautiful 240Z. The spec tire for the Open Class is the Advan A050.
