We have used both of these tires and others on Vipers and find virtually all of them quite satisfactory for the majority of drivers. There gets to be a bit of hysteria, in my opinion, about availability of various brands, and frankly it was only a bit over a year ago that Kumhos were impossible to get. Nittos, as a Japanese brand, are obviously quite likely to have a bit of a delay with the horrendous disaster in Japan, but this will also affect Yokohama, Bridgestone and many others. Kumho, as a Korean Company , should be in better shape, but as noted it was not that long ago that they were experiencing shortages. With a low volume car like the Viper , this has been a common occurence for a very long time, and in fact we have gone through periods where even the vaunted Michelins were hard to get.
As a consumer , and a Dealer, we have been pleased with Kumho, Nitto, and Michelin and are quite pleased that various manufacturers see fit to make tires to fit our beloved machines.
When viewing your purchase , tires should be viewed based on what you will use them for. Frankly my first drive on Nittos at the track ( in a different car ) brought us to the conclusion they ran better with alot higher cold temperatures than some other brands. It is even noted here that some of the guys drag racing are running traditionally high tire pressures for their trips down the strip. Michelins, in my experience, hook up a ton better with less air than noted here, work great on a road course with slightly higher than recommended street temps, yet chew themselves alive on an autocross course. In other words, even one of the best tires on the Planet for our car, the PS2, has some limitations.
Just my random thoughts, but hopefully it sheds a bit of light on the current situations and also how things have occurred in the past.
